Theses and dissertations (Applied Sciences)

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Anthropometric profile and food consumption patterns of an emerging middle income community in Umlazi
(2017) Memela, Sinenhlanhla Ntokozo; Napier, Carin E.
Introduction: The nutrition transition is a global phenomenon affected by developing economic prosperity. ‘Nutrition transition’ may be defined as changes in dietary patterns and nutrient intakes occurring in individuals, families, groups of people or whole populations when the food environment and other circumstances change. Post-1994 democratic elections in South Africa, economic laws called for the de-racialization of the economy. As a result of the annulment of the apartheid laws in the 1990s entrepreneurial opportunities became available for black people. Based on the 2011 Census, the middle class constituted 8.3 million (17%) out of the 51 million population in South Africa. Blacks made up 51%, whites 34%, coloureds 9% and Indians 6%. This is a vast difference from two decades prior to this when blacks made up only 3.3% of the population, with coloureds making up 9.1% and Indians 18.5%. In a number of Sub-Saharan African studies obesity has been shown to have a significant link to socio-economic status determined by access to water and electricity, smaller numbers of members residing in one household and increased amounts of money spent on food among other factors, which all promote a tendency to leading a more Westernised lifestyle. The main objective of the study was to determine the anthropometric status and analyse the food consumption of a community of emerging middle income status in Umlazi Township (Ward 84) outside Durban in the province of KwaZulu-Natal. Methods: This study had a sample size of n=250 adult men (n=56) and women (n=194) who were heads of households or primary caregivers above the age of 19 years old with households receiving a total household income of more than R100 000.00 per annum/ more than R8000.00 per month. The study was quantitative and descriptive in nature with different tools used to measure the sample population. These included waist circumference and height and weight measurement to determine BMI and WHtR. A socio-demographic questionnaire was completed where the multi-dimensional poverty index (MPI) was established; a food frequency questionnaire (FFQ) and three 24-hour food recall were also administered to all participants; one weekend day recall and two weekday recalls. Data were analysed on SPSS and nutrient analysis done through Food Finder Version 3 Software and compared to the World Health Organisation standards recommendations for optimal health. Results: The mean age of the group was 52 years old. Slightly more than half (51.6%; n=129) of the population was unemployed. Retired participants made up 27.2% (n=68) of the population. The majority (80%) of the households indicated that between one to three members contributed to the total household income. The MPI of the Ward 84 community amounted to 9.09. The prevalence of obesity was 37.59% (n=21) among men and 76.80% (n=149) for women. Women had a higher prevalence of risk factors linked to non-communicable diseases than men. Mineral and fat soluble vitamin intake was deficient; however protein and carbohydrates were consumed in excess with means of 187.70% and 111.43% respectively. Top 20 foods consumed lists indicated that little fruit or vegetables were consumed. The average food variety score was medium indicating the consumption of between >30 but <60 different foods across the total population. A positive relationship of statistical significance was found between food variety score and income (p=0.007). Conclusion: The Ward 84 community consisted of an ageing population with households mostly supported by another member’s income from within or outside the household. The adults had sufficient education to have secured promotions in the employment arena and could afford a lifestyle similar to that of those who had always been more privileged. Although the Umlazi residents benefited from good housing and infrastructure and appeared to have averted poverty, the prevalence of overnutrition malnutrition was high and linked with an excessive intake of macronutrients. Majority (70%) of the community of Ward 84 is ‘food secure’ as indicated by the number of participants’ households indicating never having a shortage of money to buy food. This correlates negatively with the high prevalence of overweight and obesity (BMI) (p=-0.029). According to literature a persistent issue in black communities is the acceptance of an overweight body image being perceived as ‘healthy’ and an indicator of affluence. This community appears to be in the 4th stage/ pattern of the nutrition transition. It appears that a ‘westernised diet’ and lifestyle is more accessible and is embraced by this urban community as described in various literature and seen in the top 20 foods lists compiled from the 24 hour recalls. There is some oversight regarding the nutrient quality of a varied diet and achieving energy balance with macronutrient intake linked to informed nutritional choices. Suggested interventions could include the dissemination of information regarding nutrition and practical suggestions to achieve energy balance. In addition, future research could investigate the prospects of introducing participation in urban agriculture, investigate the issue of physical activity, and foster an environment for more physical activity and increase availability and access to micronutrient dense foods and investigate the development of a body mass index specifically for the black African population.
Anti-HIV activity of selected South African medicinal plants
(2013-09-17) Hurinanthan, Vashka; Odhav, Bharti; Parboosing, Raveen
South Africa has the largest number of people infected with HIV/AIDS. It also has more than 30 000 species of plants and many of these have a long tradition of medicinal use. It is highly likely that the treatment for HIV will come from this traditional knowledge. The need for effective preventative and therapeutic agents for HIV remains an urgent global priority. The aim of this study was to screen selected South African medicinal plants for anti-HIV activity and to identify and characterise an active compound from a plant that can be used for HIV treatment. The aqueous and methanolic extracts of the roots, leaves, flowers and stems of thirty eight plant species (108 extracts) were screened for anti-HIV activity. The plants which had anti-HIV activity were further screened for anti-reverse transcriptase activity. Thirty-two extracts exhibited varying degrees of anti-HIV activity. Cleome monophylla, Dichrostachys cinerea and Leonotis leonurus aqueous leaf extracts had anti-HIV-1 reverse transcriptase activity. The aqueous extracts of D. cinerea showed the best anti-HIV activity with a Selectivity Index of 43.5 and significant anti-HIV-1 reverse transcriptase activity. Crude phytochemical screening of D. cinerea showed that it had tannins, saponins, flavonoids and alkaloids but did not contain any phlobatannins, terpenoids, steroids or phenols. D. cinerea displayed a high degree of free radical scavenging activity with an IC50 of 25 μg/ml, therefore the anti-HIV activity could be attributed to the flavonoids present in the plant. Bio-guided fractionation was used to isolate and purify the active compound from the D. cinerea extract. Compounds were isolated by thin layer chromatography and were tested for anti-HIV-1 and anti-reverse transcriptase activity. From these results the active compound was identified, and purified using preparative TLC. The active compound was characterised by High Performance Liquid Chromatography, Ultraviolet-visible spectrophotometry, and Ultra Performance liquid chromatography coupled to MS/MS. Structural elucidation was performed using Nuclear Magnetic Resonance. From these results, it was deduced that the compound isolated from D. cinerea was a catechin. In this study we show that the catechins present in D. cinerea are responsible for the anti- HIV-I activity and inhibits the reverse transcriptase activity which is a key factor in the progression of HIV. Potentially, these results can be used to develop a new drug for the treatment of HIV or as a cost effective therapeutic agent in treating HIV-infected individuals with oxidative stress.
Anti-inflammatory, anti-oxidant and wound-healing properties of selected South Africa medicinal plants
(2017) Mzindle, Nonkululeko Betty; Odhav, Bharti
South Africa has a wide range of medicinal plants that are used traditionally by black Zulu South Africans for the treatment of a range of illnesses, including inflammatory ailments; disease conditions caused by oxidative stress and wound healing. It has been indicated that bioactive compounds isolated from plants contribute to their anti-inflammatory, antioxidant and wound healing properties; hence, herbal remedies have been widely used traditionally in many countries in the management and treatment of wounds. Inflammation is the main condition that relates to a variety of diseases affecting most of the world’s population. It is the body’s immune response to infection and injury and is induced by the release of pro-inflammatory mediator’s —prostaglandins and leukotrienes—following wound occurrence. Wounds result in disruption of living tissue caused by oxidative stress. Anti-inflammatory agents, antioxidants, and antimicrobials play an important role in the wound healing process and they prevent aggravated wound conditions.Controlling inflammation during wound repair is important to minimize any additional complications that may result; hence, chemical agents such as non-steroidal anti-inflammatory drugs (NSAIDS), synthetic antioxidantsand steroids are frequently used. These drugs block the enzymes that are responsible for prostaglandin synthesis in inflammation, react with free radicals thereby interfering with oxidation process as a result affect one or more phases of wound healing. The use of these drugs, however, has been limited as they can cause detrimental side effects when used over long periods of time.There is, consequently, a need to find alternative natural therapeutic drugs. Studies on medicinal plants confirmed that herbal drugs exhibit fewer side effects in comparison with chemical agents and are more cost-effective.Thus the aim of this study was to investigate South African medicinal plants, for anti-inflammatory, antioxidant and wound healing properties. Dissolved extracts of thirty-eight medicinal plants were evaluated for theiranti-inflammatory activity using the 5-lipoxygenase assay as well as free radical scavenging activity using the 1; 1-diphenyl-2-picrylhydrazyl (DPPH) assay.Their safety was evaluated using brine shrimp lethality assay. Proliferation and viability of fibroblast cells was determined by the3-(4, 5-dimethylthiazolyl)-2, 5-diphenyltetrazolium bromide(MTT) assay furthermore a scratch wound assay was used to study the properties of wound healing in vitro and to confirm the anti-inflammatory activities of the dissolved extracts. Migration rate was evaluated quantitatively by an image analyzer. Methanol was chosen for extraction because it completely dissolves extracts. Anova was used for statistical analysis. Almost all aqueous extracts were found to be effective in inhibiting lipoxygenase enzyme when compared to nordihydroguaiaretic acid (NDGA). Aqueous extracts exhibited remarkably high percentage inhibition of lipoxygenase with most above 100% when compared to methanolic extracts. Amaranthus dubius and Portulaca oleracea were found to have good biological activities in the inhibition of 5-lipoxygenase enzymes when compared to the other plants. However, Galinsoga parviflora and Syzygium cordatumwere least effective in inhibiting enzyme activity with percentages as low as -2% and 34% respectively. Percentage inhibitions for methanolic extracts were lower than that of aqueous extracts. Amaranthus spinosus had the highest percentage inhibition among all the methanolic extracts andGalinsoga parviflorahad the lowest. The methanolic plant extracts were found to be more effective in scavenging DPPH free radicals than the corresponding aqueous extracts. All the methanolic extracts exhibited free radical scavenging ability in the range of 60%–104%. Asystasia gangetica, Ficus sur, Heteropyxis natalensis, Hibiscus sabdariffa, Pelargonium sp. showed notably higher scavenging abilities, ranging from 101%–104% compared to Rutin. Methanolic extracts of Heteropyxis natalensis and Hibiscus sabdariffa exhibited scavenging ability even at the lowest concentration of 10μg/ml. Furthermore, aqueous extracts displayed remarkably lower activities than methanolic extracts with thirty-one extracts having a scavenging capacity ranging from 22%—59%. None of the extracts were found to be detrimental to brine shrimp. Almost all the extracts were shown to stimulate the growth of fibroblast cells except the methanolic extract of Solanum nodiflorum, which was shown to be killing the cells at high concentrations with a percentage viability of 46%.As the concentration decreased, however, the viability of cells with this extract increased to 143%. An increase in the number of fibroblast cells was observed in the scratched area of the treated cells and a significant migration rate was also noted with some of the extracts. Aqueous extracts of Sonchus oleraceus (86%), Justicia flava (85%) and Dichrostachys cinerea (85%) and methanolic extracts of Senna occidentalis and Hibiscus sabdariffa were found to have the highest migration rate compared to untreated cells that served as a control. No cell migration was observed with methanolic extract of Solanum nodiflorum.Instead, the extract was found to be toxic to the cells. Some of the plants evaluated in this study have been studied for either anti-inflammatory, antioxidantand wound healing properties in vivo, however, no work has been conducted to demonstrate a correlation between anti-inflammatory, antioxidant and wound healing properties of plant species in vitro. The current study was, therefore, conducted to review medicinal herbs considered as anti-inflammatory, antioxidants and wound healing agents as well as collecting evidence for their effectiveness and pharmacological mechanisms in modern science. In the plant species investigated Amaranthus dubius, Asystasia gangetica, Bidens pilosa, Buddleja saligna, Carpobrotus dimidiatus, Chenopodium album, Dichrostachys cinerea, Emex australis, Ficus sur, Guilleminea densa, Hibiscus sabdariffa, Physalis viscose, Syzygium cordatum, Taraxacum officinale and Tulbaghia violacea demonstrated good anti-inflammatory and wound healing properties.In conclusion the results from this study demonstrated promising anti-inflammatory and antioxidantactivities as well as wound healing properties,furthermoreit was aslo shown that the plant extracts were not toxic to the cells hencethis suggested that the plants investigated, can be used as substitutes or to formulate wound healing agents that are safe to use in primary healthcare.
Application of lipid extracted algae in feed and energy production
(2019) Ansari, Faiz Ahmad; Bux, Faizal; Gupta, Sanjay Kumar; Guldhe, Abhishek
Microalgae are well considered to be promising feedstocks for biodiesel production. Microalgae can be grown under different types of cultivation conditions and their biomass has tremendous potential to be used as biofuel feedstock and for other applications such as feed, food, cosmetics, pharmaceutical etc. Despite the many benefits and the significant development in the field of microalgal biodiesel production, there are several challenges including high cultivation cost and developing efficient downstream processing methods. The biomass production cost is high, which significantly hinders the use of microalgae as a feedstock. Most of the available literature is focused on upstream, single strain and single product strategy, where mainly algal lipids are used for biofuel production. Hence, for improving the sustainability of the algal biofuel production processes and related process economics, a multiple applications approach using integrated biorefinery and exploiting microalgae for environmental benefits is required. To explore the microalgal biorefinery concept it is vital to understand the various cultivation conditions and applications of biomass in different sectors. There are various strategies, which have potential to make algal biofuel technologies more economically feasible and environmentally sustainable. Use of alternative culture media, improving the biomass production and the efficiency of downstream processing (drying, cell disruption, lipid extraction etc.) algal biofuel technology economical. Utilizing lipid-extracted algae (LEA) for energy and aqua feed application will maximize overall economic return and will leave minimal residues as by-product. The major focus of this thesis was to utilize LEA as substrate for biomethane production and protein source in aquaculture feed. However, effect of preceding steps such as microalgae cultivation, biomass drying and cell disruption on major metabolites extraction was also studied. Microalgae were cultivated in different medium (domestic wastewater and BG11) and their biomass yields and biochemical composition (lipid, protein and carbohydrate) were compared. Different drying and cell disruption techniques were employed for lipid extraction and their effect on lipid, protein and carbohydrate yields were evaluated. The yield of major metabolites on whole cell and LEA were also compared. Suitable solvent systems were selected for optimum lipid extraction from wet and dry biomass with minimal toxic effect on LEA metabolites so that LEA can be further used for biomethane and aquaculture feed production. The choice of microalgae at large scale depends upon the number of factors such as their adaptability to large-scale cultivation, biomass production, major metabolites content, robustness towards the open system cultivation and contamination. In this study, S. obliquus and C. sorokiniana were cultivated in wastewater and BG11 medium at laboratory scale. Both strains are indigenous to KwaZulu-Natal. C. sorokiniana showed lower biomass and major metabolites (lipid, protein and carbohydrate) production at large scale compared to S. obliquus. Considering better adaptability to open cultivation, high biomass and metabolites yields, S. obliquus strain was selected for the LEA application study. Microalgae species, C. sorokiniana and S. obliquus were cultivated on BG11 and using different ratios of raw domestic wastewater and post-chlorinated wastewater as nutrient media. The cultivation of S. obliquus and C. sorokiniana showed biomass yield of 1.2-3.5 and 0.78-1.8 g L-1 in BG11 medium, respectively. While biomass yield observed in wastewater was 0.59-1.59 g L-1 for S. obliquus and 0.67-1.45 g L-1 for C. sorokiniana. The higher biomass yield in BG11 medium attributed to the higher nutrient contents in this medium compared to wastewater. The lipid contents for S. obliquus and C. sorokiniana were 20 and 16.5% dry cell weight (DCW), respectively when grown using BG11 medium. While increases in lipid contents of 26.25 and 29.4% DCW were found for S. obliquus and C. sorokiniana, respectively when cultivated using wastewater. Similarly, carbohydrate contents for S. obliquus and C. sorokiniana were 18 and 17% DCW, respectively for BG11 medium. Increased in carbohydrate contents of 25% for S. obliquus, 28.4% DCW for C. sorokiniana were observed for wastewater. Microalgae tend to accumulate more lipids and/or carbohydrates under nutrient stress condition. The nitrogen and phosphorus contents in wastewater are lower than BG11 medium, which were responsible for stressed condition for microalgae. With limited nutrients in wastewater compared to BG11 medium, growth of microalgae is also lower which resulted in lower protein content. Protein content for S. obliquus and C. sorokiniana in BG11 medium were 37.83-48.8 and 25-35.3% DCW, respectively. The protein contents for S. obliquus and C. sorokiniana in wastewater medium were 16.4-27.29 and 15.8-27.3% DCW, respectively. The biochemical composition depends upon the nutrient composition of the medium and cultivation conditions. The two selected microalgae have shown potential for nutrient removal while cultivated in wastewater. The removal efficiency by S. obliquus was found to be 76.13% for COD, 98.54% for nitrogen and 97.99% for phosphate. Microalgae C. sorokiniana cultivation in wastewater removed 69.38% COD, 86.93% nitrogen and 68.24% phosphates. Increased lipid accumulation in the cells was also recorded in stressed conditions due to low nutrient availability from wastewater. After harvesting of microalgae from culture media, the water content in thick algal slurry (>85% DCW) lowers the products recovery. To overcome this challenge drying and cell disruption are required to enhance the efficiency of lipid extraction. Where drying and cell disruption increase the viability of biomass for lipid extraction process. Three biomass-drying techniques viz. sun, oven and freeze-drying and four-cell disruption techniques viz. microwave, sonication, osmotic shock and autoclave disruption were studied for their effect on recovery of major metabolites from S. obliquus. Microalgae metabolites recovery from whole cell and LEA were analysed and compared. The results showed that after lipid extraction, LEA still contained comparable protein to whole algae biomass however, the carbohydrate concentration was reduced. Oven drying exhibited the highest recovery of all the major metabolites followed by freeze-drying; sun drying however, showed lower yields. Despite lower metabolites recovery sun-drying technique is preferable at large scale due to its easy application and cost-effective nature. The main drawback of sun drying technique is weather dependence and required longer period to dry. The microwave and autoclave microalgal cell disruption improved the lipid yield but loss of other compounds was observed. In osmotic shock treatment, due to poor cell disruption efficiency low lipid were obtained and comparably lower protein loss was noticed during lipid extraction. Lipid extraction is crucial step for microalgae biodiesel production. Solvent-assisted lipid extraction is widely used technique for lipid recovery from dry or wet algae biomass. In a biorefinery approach, it is vital to choose appropriate solvents for the optimum lipid extraction whilst having minimal effect on the remaining metabolites (protein and carbohydrates) in LEA. LEA could be used for energy generation or aquaculture feed applications. Six commonly used organic solvents/ solvent systems were used for lipid extraction from wet and dry biomass. The results showed that the lipid extraction efficiency depends strongly on types of biomass as well as solvent systems selected. Lipid extraction from wet algal biomass could reduce the processing steps and save energy incurred in drying. However, the water present in wet algal slurry acts as a barrier, which results in lower lipid yield compared to the dry biomass. The results revealed that among all six-selected solvents, chloroform: ethanol (1:1 v/v) was most effective if wet biomass used specifically for lipid purpose only. To explore the biorefinery concept, isopropanol/hexane composition is the most suitable solvent system because it is less toxic and resulted in high protein (20.07% DCW) and carbohydrate (22.87%) yields in LEA. For dry algal biomass, chloroform: methanol (2:1 v/v) is an appropriate solvent system if biomass used especially for lipid (19.25%) extraction. If LEA to be used for energy and/or aquaculture feed application, DCM: methanol was found to be a suitable solvent system, which gave 32.79% protein and 26.92% carbohydrate yield. Comparatively hexane has lower lipid recovery but shown higher protein and carbohydrate yield in LEA. Due to less toxic, easy to scale up and inexpensive, hexane is preferable as a solvent for lipid extraction if LEA is to be further utilized at large scale for energy or feed application. Anaerobic digestion (AD) of organic residues is well-researched technology for biomethane production. Whole microalgae and LEA has promising potential for biomethane production. The anaerobic sludge used as inoculum for microalgal biomass digestion. Biomethane production from whole algae and products extracted algae highly depends on sludge to algae biomass ratio for higher methane production. The extraction of metabolites also changes the biochemical composition of residual biomass, which can affect the biomethane production. It is vital to understand the effect of various product-extracted algae and as well as pre-treated algae on the biochemical methane potential. In order to compare biomethane potential, four types of biomass were selected namely sun dried powder algae (SDPA), mild heat-treated algae (MHTA), LEA (using hexane as lipid extracting solvent) and protein-extracted algae (PEA). The average methane (CH4) production rate was ~ 2.5 times higher for protein and lipid extracted algae than for whole algae SDPA and MHTA whilst the cumulative CH4 production was higher for pre-treated algae. Highest cumulative CH4 production (318.7mL CH4 g-1 VS) was found for MHTA followed by SDPA (307.4mL CH4 g-1 VS). The CH4/CO2 ratios of 1.5 and 0.7 were observed for MHTA and LEA, respectively. Outcome of this objective revealed that pre-treatment process disrupts the microalgae cell walls, exposing intracellular material and increasing the surface area. The product-extracted algae changes the elemental composition, which decreases the cumulative gas yield CH4/CO2 ratio. Presence of high nitrogen in the form of protein produces ammonia (NH3) which inhibits the methane production. Therefore, it is imperative to use PEA biomass to improve the methane production yield than the whole cell biomass. Due to escalating price and unstable supply of fish meal (FM), alternative protein sources are used in aqua feed, however these sources do not meet to the requirement. The use of less expensive protein source in aquaculture feed as alternative to FM is required. Microalgae are primary producers in the food chain as well as a natural food for fish. Microalgal biomass is comprised of proteins, lipids, carbohydrates, pigments and many other bioactive compounds. The microalgal proteins have an appropriate balance of all essential amino acids, while lipids are rich in polyunsaturated fatty acids (omega-3 fatty acids, EPA, DHA). Whole algae contain all required ingredients while LEA also contain protein, carbohydrates, vitamins, bioactive compounds even though most of the lipid soluble nutrients have been removed. Thus, microalgae have promising potential to be used in aquaculture feed. Aquaculture production continues to increase globally, to meet the aquaculture feed demand algae supplemented aquaculture feed will play an important role in providing good quality fish. In this study, approximately 200 kg of microalgal biomass was harvested for the feed application. Due to lower toxicity, ease of availability and ease of recovery from mixture, hexane was used as a lipid extracting solvent at pilot scale to generate LEA. The 44 weeks (from juvenile to finisher stage) feeding trials were conducted to evaluate the effect of whole and LEA supplementation of S. obliquus strain on growth performance, disease tolerance, feed utilization, physiological activity, and fillet biochemical composition of Nile tilapia (Oreochromis niloticus). In the first trial, fish were fed with an algae free diet (control) and four experimental diets (2.5, 5, 7.5 and 10 wt%) as protein source of dried S. obliquus. The study showed that microalgae could be used as a protein supplement in the Tilapia feed for enhancement of morphological characteristics and nutritional value. The 7.5% and 10% supplementation of whole algal biomass in tilapia feed showed significant improvement in weight and length of the fish compared to the control. The daily body weight gain was 0.25 g higher in experimental groups than the control. The hepatosomatic index percentage was also higher in fish feed when 7.5% whole algae was used in fish feed as a protein source. The results also showed that 7.5% and 10% have better specific growth rate (1.57 and 1.5%), daily body weight gain (1.1 and 0.86 g), overall body weight gain (427.16 and 331.48 g), protein assimilation (43.96 and 40.46%) higher than the control diet fed fish. The survival rate of fish were 100% at every inclusion level. In second trial (44 weeks), two supplementations (7.5 and 10 wt%) of LEA as protein source were used in Nile tilapia diets. Results showed 7.5% and 10% LEA supplemented feed shown better growth performance than control. The protein content were 42.2%, 41.3% and 36.1% in tilapia fed with 7.5%, 10% LEA and control feed, respectively. The body weight gain, tilapia fed with 7.5% LEA shown 357 g while 10% LEA and control have 331.78 g, and 330.08 gm, respectively. The application of whole and LEA of S. obliquus in tilapia feed, shown appropriate supplementation level for tilapia feed at demonstration scale. This thesis presents advances in knowledge in the field of microalgae biorefinery research for pilot scale operations. This research work has covered various aspects such as effect of drying, cell disruption and lipid extraction on whole and LEA metabolites yield. The extraction of lipid from wet and dry microalgal biomass using various solvent systems provides a new insight for the selection of appropriate solvent systems, which can be used for the large-scale lipid extraction. The study on LEA for biomethane production enhances the understanding about the effects of different pre-treatments and product extractions on biomethane production. The results revealed that the supplementation of whole cell and LEA using S. obliquus for tilapia feed is safe therefore, can be used as an alternative protein source. The findings of this study have both academic and industrial value.
Application of thermostable a-Amylase from Thermomyces lanuginosus ATCC 58157 to nutritionally enhance starch based food
(2006) Padayachee, Thiriloshani
In Sub-Saharan Africa there is an urgent need to sustain and improve the quality of its food resources. Poverty eradication features high on the agenda of a number of world health organisations, while the number of underweight children in Africa continues to increase (Pellet, 1996). Providing nutritionally enhanced foods to the poor will help towards achieving this objective. Protein-energy malnutrition has been identified as one of the most important problems facing Africa, with maize as the staple diet (Nkama et al., 1995). However, a combination of several factors limits availability and the nutritional quality of maize. During starvation, energy and protein intakes decrease by 20-30%, with most of the children in Africa having an average protein intake of only 20 g per day (Igbedioh, 1996). Energy availability also affects protein utilization because of interrelationships of protein and energy metabolism (Elwyn, 1993). The diets of inhabitants in developing regions depend mainly on cereals (maize) for both protein and dietary energy which lacks indispensable amino acids, minerals, vitamins and carbohydrates. In light of these growing concerns an attempt was made to devise a scientific strategy to combat the nutritional shortfalls of maize meal. A multidisciplinary and concerted approach was followed within this project aimed at designing an improved thermostable amylase and applying the enzyme to nutritionally enhance maize meal. It was envisaged that the manipulation of maize meal, by the application of enzyme technology will improve the nutritional status of this staple food. The consequences is that an alternate solution for the eradication of an ailing, poverty stricken and malnourished African population is achievable. It is possible that the boundaries defining the limits of life will extend to even greater extremes through the application of novel technologies.
Assessing milk quality using the electronic nose
(2007) Govender, Samantha
There are many ways for milk and dairy products to develop flavour defects. Sensory evaluation, has been the traditional approach to characterize off flavours. The need for odour sensing devices becomes greater when volatile and semi-volatile organic compounds are present in the product in parts per billion or even in the parts per trillion concentration range that cause off flavours. Today, sophisticated, sensitive instrumental tests such as electronic nose technology coupled with gas chromatography are capable of detecting, identifying and quantifying the specific chemical agents responsible for off flavours. This study focused on the use of the electronic nose as a novel technology for the detection and monitoring of milk quality by testing the effects of heat treatment at 63˚C and shelf life. Microbiological testing, sensory evaluation and gas chromatographic analysis were carried out together with aroma profiling using the electronic nose to determine milk quality.
Assessment of microalgal ACCase and rbcl gene expression as a function of nutrient and metal stress
(2017) Singh, Poonam; Bux, Faizal; Kumari, Sheena K.; Guldhe, Abhishek
Microalgae are considered to be a potential feedstock for biodiesel production. However, the main concern with regard to the large scale microalgal biodiesel production process is its competence and economic viability. The commercial realization of microalgal biodiesel production requires substantial impetus towards development of efficient strategies to improve lipid yields upstream. Nitrogen (N) and phosphorus (P) stress during cultivation are the widely used lipid accumulation strategies for microalgae. However, these individual nutrient stress strategies are associated with compromised biomass productivity which hampers overall lipid productivity. Lipid enhancement strategies based on light, temperature and CO2 are associated with technological barriers for scale up and incur additional cost. Thus, the main aim of this study was to develop an integrated, easily applicable and scalable lipid enhancement strategy based on nutrients and metals such as N, P, iron (Fe), magnesium (Mg), calcium (Ca) and EDTA stress for selected indigenous microalgal strains. The effect of metal concentrations individually and in combination on microalgal lipids and biomass production is a scarcely exploited area. In this study, a novel approach involving individual as well as combined metals and EDTA stress under N and P limited conditions for lipid enhancement in microalgae was investigated. Microalgal growth physiology, photosynthetic performance, biochemical composition (lipid, carbohydrate and protein) and expression of selected key genes involved in photosynthesis (rbcL) and fatty acid biosynthesis (accD) were studied both under selected individual and combined stress conditions. Out of seven microalgal isolates obtained during the initial isolation and screening process, two strains were selected for lipid enhancement study based on their growth rates, biomass yields, lipid content and lipid productivities. The strains were later identified as Acutodesmus obliquus and Chlorella sorokiniana based on both morphological characteristics and phylogenetical analysis. The selected strains were thereafter subjected to different cultivation conditions involving varying metal, EDTA and nutrient stress conditions. A significant increase in lipid productivity was observed when the concentrations of Fe, Mg and EDTA were increased and Ca was decreased to degree in the N and P stress BG11 medium. For A. obliquus, a highest lipid productivity of 80.23 mgL-1d-1 was achieved with the developed strategy under limited N (750 mg L-1) condition which was 2.18 fold higher than BG11 medium and 1.89 fold higher than N limited condition alone. Similarly, for C. sorokiniana, highest lipid productivity of 77.03 mgL-1d-1 was achieved with the developed strategy under limited N (500 mgL-1) and P (10 mgL-1) which was 2.67 fold higher than BG11 medium and 2.35 fold higher than N and P limited condition alone. For both the microalgal strains, Fe was the most significant trace metal affecting their lipid productivity. These above observations were further confirmed through photosynthetic performance analysis and gene expression studies. At mid log phase, 6.38 and 5.15 fold increases in the expression levels of rbcL gene were observed under combined stress (OCMS+OE) as compared to the control (BG11) condition in A. obliquus and C. sorokiniana respectively. This also resulted in an increased expression level of accD gene involved in lipid biosynthesis to 10.25 fold and 9.79 fold in A. obliquus and C. sorokiniana respectively at late log phase. The results from expression studies of rbcL and accD genes were in compliance with biomass yields, photosynthetic performance, protein yield and lipid productivities for both the strains under different cultivating conditions. The universal applicability of the above strategy was confirmed by applying it to five other microalgae strains isolated in this study which resulted in considerable increase in their overall lipid productivity under optimized conditions. Attempts were made to scale up the lab scale study to open circular pond (3000L) cultivation for A. obliquus. Results showed a 2.08 fold increase in lipid productivity under optimized conditions compared to the control, which emphasizes the scalability of the developed strategy even under uncontrolled conditions. In conclusion, the developed combined metal and EDTA stress strategy not only assisted in alleviating the biomass productivity but also enhanced the lipid accumulation which resulted in overall increased lipid productivity under N and P limited condition. Furthermore, the improved carbohydrate and protein productivities observed with the developed lipid enhancement strategy make it suitable for biorefinery approach with multiple products. An improvement in lipid profile and high biodiesel conversion were also observed with this universally applicable and scalable lipid enhancement strategy confirming their potential applicability during large scale cultivation for biodiesel production.
Characterization and modification of Bambara groundnut globulin fractions for the enhancement of functional properties
(2023-05) Alabi, Opeyemi Olaitan; Amonsou, Eric Oscar
There is a growing interest in the utilization of leguminous grain proteins for food and industrial applications. Bambara groundnut is a xerophyte pulse grain and a potential source of protein that can replace soybean protein, a trusted and widely used food ingredient in the food industry. However, the use of Bambara groundnut proteins including the subunits (legumin and vicilin) is limited in food applications. The understanding of the composition of Bambara groundnut proteins at the subunit level is vital to unlocking their potential and facilitating utilization. In this study, Bambara groundnut globulin is characterized in terms of the structures, composition, and physicochemical properties at the subunit level, and then modified using atmospheric plasma and enzymatic hydrolysis. Bambara globulin consisted of about 70% vicilin, whilst legumin protein was found in relatively low quantity. Gel electrophoresis revealed three major protein bands in globulin similar to vicilin with predominant β-sheet structures. The presence of a disulfide bond was also revealed in legumin. Bambara globulin showed major vicilin (7S, Mw: 120 kDa) and minor legumin (11S, Mw: 410 kDa) components. Fluorescence and hydrophobicity data suggested a folded structure for the legumin fraction dominated by the helical secondary structure compared to the vicilin fraction. Bambara proteins contain an appreciable amount of methionine that is even higher than the FAO/WHO recommended value. Bambara vicilin had the highest amount of negatively and positively charged amino acids compared to globulin and legumin. This coincides with its high solubility profile (approximately 82% at pH 3.5). The least gelation concentration (LGC) significantly increased in the order of globulin (8%) < legumin (18%) < vicilin (20%) at pH 7. Bambara groundnut proteins formed weakly structured gels as indicated by the frequencydependent behaviours of both the storage (Gʹ) and loss (Gʺ) moduli with a difference of lesser than 1 log cycle. The highest Gʹ of vicilin gel indicated more firmness of the gel compared to the gel formed by globulin and legumin. The sol-gel transition temperatures increased in the order of globulin (40℃) < legumin (50℃) < vicilin (80℃). The Gʹ and Gʺ of globulin showed relatively low dependency on heating time beyond the gel point compared to legumin and vicilin subfractions, suggesting a more rapid establishment of its gel network during gelation. Vicilin gel consisted of a microporous structure with a small lath sheet-like structure compared to globulin and legumin. Emulsifying stability of the proteins significantly differed (p < 0.05) at pH 7. The foaming capacity of the vicilin fraction was significantly (p < 0.05) higher than that of the storage protein at pH 3, 7, and 9. Atmospheric cold plasma-activated water (PAW) and enzymatic modification of Bambara groundnut globulin were further assessed. The cold plasma treatment resulted in the loss of the helical structure of Bambara globulin. The plasma treatment increased the hydrophobicity of Bambara globulin indicating an unfolded structure that was also reflected in the observed redshift in fluorescence intensity. No major changes were observed in gel electrophoresis, protein surface charge, and solubility profiles, except for about a 20% reduction in the glutamic acid content of the amino acid profile. Bambara globulin had reduced emulsifying capacity after treatment with PAW. However, foaming capacities were significantly better and stable at up to 15 mg protein/mL. Hydrolysates produced from Bambara groundnut globulin and vicilin, respectively using a combination of pepsin and pancreatin were investigated for ACE and renin inhibitory activities. The hydrophobic amino acid residues in both globulin and vicilin hydrolysates are high, improving the entry of their peptides into target organs via hydrophobic associations. Surface hydrophobicity increased significantly (p<0.05) with an increase in peptide size from <1 to <3 kDa with that of vicilin hydrolysate and membrane fractions having the highest values. The low molecular weight peptide (<1 kDa) membrane fractions from globulin at 1 mg/mL exhibited significantly higher (p<0.05) invitro ACE inhibitory activities compared to vicilin hydrolysate and its fractions. However, higher molecular peptide fraction (<3 kDa) favoured renin inhibitory activity at the same concentration. Vicilin is the major protein fraction of Bambara groundnut globulin. Bambara groundnut globulin was stabilized by disulfide linkages from the legumin, a minor fraction of the storage protein. Bambara globulin and its subfractions formed a weakly structured gel with the dominance of an elastic structure. The dominancy of the β-sheet structure in vicilin protein and the high crosslink density of the vicilin gel could be related to the firmness of the vicilin gel. The variations in the gel points of Bambara globulin and the subfractions were linked to the differences in their amino acid and subunit composition, the thermal unfolding properties of the protein fractions, and the presence of disulfide linkages. Modification of Bambara groundnut globulin using cold plasma-activated water treatment and enzymatic hydrolysis, respectively increased the hydrophobicity of the protein and influenced the emulsifying and foaming properties and the invitro angiotensin-converting enzyme (ACE) and renin inhibitory activities. Therefore, Bambara groundnut globulin could be a potential functional ingredient in the food system. The low molecular weight peptide (<1 kDa and <3 kDa) membrane fractions from globulin have the potential to serve as functional bioactive peptides against hypertension.
Computational studies of the folding patterns of small and medium-size polypeptides
(2010) Mokoena, Paul; Bisetty, Krishna; Perez, J. J.; Corcho, F. J.
This study involved a series of molecular dynamics (MD) simulations applied to case studies of small and medium-size polypeptides to assess the thermodynamics of their folding characteristics. Peptide folding is a complex and vital phenomenon taking place in all living systems. Bioactive conformational structures of folded peptides need to be well characterized before using them in computer-aided drug design. The computational procedure was validated on the 10-residue long chignolin-like synthetic mini-protein (CLN025). For this peptide, replica exchange molecular dynamics (REMD) calculations were carried out in explicit and implicit solvents using the generalized Born (GB)/surface area (SA) approximation with different sets of force field parameters. Following this validation procedure, case studies of the folding conformations of peptides of different lengths including the 5-residue met-enkephalin, the 27-residue pituitary adenylate-activating polypeptide 27(PACAP27) and the 28-residue vasoactive intestinal peptide (VIP) were undertaken. The latter two peptides are multifunctional hormones that mediate diverse biological functions, such as the cell cycle, cardiac muscle relaxation, immune response, septic shock, bone metabolism, and endocrine function. Results obtained indicate that when explicit water, methanol and DMSO solvents were used, it appeared that methanol (MeOH) and dimethylsulphoxide (DMSO) afforded met-enkephalin the ability to form more intra-hydrogen bonds than water, producing type I and type III β-turn structures; thus enhancing the helical conformation of the peptide. MD trajectories of longer polypeptides (VIP and PACAP27) were also populated with type I and type III β-turns, which occurred consecutively; with α- and 310-helices occurring from the middle of each peptide towards the C-terminal. Characterization of implicit solvent results, reveal that these simulations have been able to reproduce the same type of conformers obtained by experimental NMR studies published in literature, which structurally resemble the native conformation of the bioactive peptides. These conformational structures will be applied as lead agents in computer-aided drug design. One of the major achievements of this study is the ability to optimize and validate the force field parameter sets to describe the thermodynamic properties of peptide systems in an unbiased manner, a non-trivial task for even the smallest of peptides. These findings re-affirm the notion that computational methods have matured enough to model dynamic biological phenomena such as peptide folding, a feat previously thought to be impossible.
Criteria based academic and vocational predictor elements for student selection in the National Diploma of Food Service Management programme
(1996) Koen, Pauline Anne; Coertze, Dirk J.
As tertiary institutions, technikons are in the fortunate position that there is a demand for their educational programmes among prospective students, and an equally positive demand for technikon diplomates from the relevant industries who require skilled manpower. Unfortunately resources are limited and thus technikons cannot admit all the applicants who apply for the various courses. For this reason it has become essential to select only those candidates who are most likely to complete the educational training programmes, and fit successfully into the job market. When the value and nature of technikon education are compared to those of a university education, it seems appropriate that their respective students should possess different qualities and abilities, which should be accommodated in the selection criteria governing enrolment.
Design and operation of a laboratory scale photobioreactor for the cultivation of microalgae
(2011) Bhola, Virthie; Bux, Faizal
Due to greenhouse gas emissions from fossil fuel usage, the impending threat of global climate change has increased. The need for an alternative energy feedstock that is not in direct competition to food production has drawn the focus to microalgae. Research suggests that future advances in microalgal mass culture will require closed systems as most microalgal species of interest thrive in highly selective environments. A high lipid producing microalga, identified as Chlorella vulgaris was isolated from a freshwater pond. To appraise the biofuel potential of the isolated strain, the growth kinetics, pyroletic characteristics and photosynthetic efficiency of the Chlorella sp was evaluated in vitro. The optimised preliminary conditions for higher biomass yield of the selected strain were at 4% CO2, 0.5 g l-1 NaNO3 and 0.04 g l-1 PO4, respectively. Pulse amplitude modulation results indicated that C. vulgaris could withstand a light intensity ranging from 150-350 μmol photons m-2s-1. The pyrolitic studies under inert atmosphere at different heating rates of 15, 30, 40 and 50 ºC min-1 from ambient temperature to 800 oC showed that the overall final weight loss recorded for the four different heating rates was in the range of 78.9 to 81%. A tubular photobioreactor was then designed and utilised for biomass and lipid optimisation. The suspension of microalgae was circulated by a pump and propelled to give a sufficiently turbulent flow periodically through the illuminated part and the dark part of the photobioreactor. Microalgal density was determined daily using a Spectrophotometer. Spectrophotometric determinations of biomass were periodically verified by dry cell weight measurements. Results suggest that the optimal NaNO3 concentration for cell growth in the reactor was around 7.5 g l-1, yielding maximum biomass of 2.09 g l-1 on day 16. This was a significant 2.2 fold increase in biomass (p < 0.005) when compared to results achieved at the lowest NaNO3 cycle (of 3.8 g l-1), which yielded a biomass value of 0.95 g l-1 at an OD of 1.178. Lipid accumulation experiments revealed that the microalga did not accumulate significant amounts of lipids when NaNO3 concentrations in the reactor were beyond 1.5 g l-1 (p > 0.005). The largest lipid fraction occurred when the NaNO3 concentration in the medium was 0.5 g l-1. Results suggest that the optimal trade-off between maximising biomass and lipid content occurs at 0.9 g l-1 NaNO3 among the tested conditions within the photobioreactor. Gas chromatograms showed that even though a greater number of known lipids were produced in Run 8, the total lipid percentage was much lower when compared to Runs 9-13. For maximal biomass and lipid from C. vulgaris, it is therefore crucial to optimise nutritional parameters such as NaNO3. However, suitable growth conditions for C. vulgaris in a tubular photobioreactor calls for innovative technological breakthroughs and therefore work is ongoing globally to address this.
Detection and quantification of nitrifying bacteria from South African biological nutrient removal plants
(2013-07-30) Ramdhani, Nishani; Bux, Faizal; Pillai, Sheena Kumari Kuttan
Nitrification is a crucial step in biological nutrient removal (BNR) processes, mostly carried out by a group of nitrifying bacteria which includes ammonia-oxidising bacteria (AOB) and nitrite-oxidising bacteria (NOB). Nitrification failure has proven to be a common operational problem in full-scale wastewater treatment plants (WWTP) since nitrifying bacteria are very sensitive to sudden changes in environmental or plant operating conditions. The current investigation was carried out to advance our understanding of the distribution of nitrifying bacterial populations and their performance at three different BNR plants in KwaZulu-Natal, South Africa. The latest molecular techniques such as fluorescent in situ hybridisation (FISH)-confocal scanning laser microscopy (CSLM), polymerase chain reaction (PCR) and real-time quantitative PCR (Q-PCR) were applied to detect and quantify nitrifying bacteria. When using FISH to target the nitrifying population, it necessitated optimising pre-treatment protocols of the samples to improve accuracy during quantification. Sonication was found to be the superior method of dispersion based on the least disruption of nitrifier cell integrity, irrespective of the sludge type. The effect of plant configurations and wastewater characteristics on the distribution of the nitrifying bacterial population and subsequently on the nitrification performance was evaluated using FISH and PCR. FISH results revealed the dominance of Nitrosomonas (AOB), Nitrobacter (NOB) and Nitrospira (NOB) for all BNR plants. The 16S rRNA analysis of PCR products using genus-specific primers, revealed the presence of more than one species of the same group at these plants. Nitrosomonas spp. including Nitrosomonas halophila, Nitrosomonas eutropha, Nitrosomonas europaea, Nitrosomonas aestuarii and an unidentified Nitrosomonas spp. were found to dominate among the AOB and Nitrobacter vulgaris, Nitrobacter alkalicus, Nitrobacter hamburgensis and an unidentified Nitrobacter spp. were the dominant species for NOB. Among these species, Nitrosomonas aestuarii, Nitrosomonas europaea, Nitrobacter hamburgensis were detected only from the industrial wastewater samples. The efficiency of two commonly used techniques viz., FISH and Q-PCR for the detection of nitrifiers from WWTP were also studied and compared, specifically targeting Nitrobacter sp. Even though there were slight variations in the quantification results, changes in the Nitrobacter community at these plants were consistent for both FISH and Q-PCR results. Both techniques have their own limitations and advantages. This study has helped to add to the platform of understanding the distribution and activity of nitrifying bacteria by correlating population dynamics with the operational parameters at full-scale level. The observations made in this study will assist researchers and engineers to minimise future nitrification failure at full-scale BNR plants. This study also confirmed the highly complex activities of wastewater treatment processes, which is dependant on a number of factors. Specific AOB or NOB predominant in wastewater rather suggests that the wastewater type and characteristics may contribute to significantly different microbial environments. Among the AOB, Nitrosomonas dominated at all BNR plants throughout the study period and for NOB both Nitrobacter and Nitrospira were found in significant numbers but their dominance varied across the plants. These dissimilar, distinct distribution patterns could be attributed to their environment which in turn impacted on the nitrification performance of the system. It was also noted that the co-existence of more than one group of these communities at the same plant could help the plant escape complete functional failures such as nitrification, due to sudden changes in temperature and substrate concentrations, as this function can be performed by different groups. Although it would have been meritorious to conduct a nitrogen balance in this study, this was not possible since the research focused on full-scale systems.
Development of a sensorially acceptable food product from Cissus quadrangularis to create awareness among young adults
(2021) Singh, Vihara; Naicker, Ashika; Palmer, Karina
Among the main causes of food insecurity in Africa is drought which results in poor harvests for farmers. Drought tolerant plants are environmentally sustainable and show great promise in improving food security and preventing malnutrition. South Africa has a wide range of drought tolerant indigenous plants that possess both medicinal and nutritional value. However, most of these indigenous plants are used by older generations and are unfamiliar to younger generations. With the revival of indigenous knowledge systems and botanical decolonisation, the potential of indigenous plants as functional foods has come to the fore. Aim: The aim of this study is to develop a sensorially acceptable food product with Cissus quadrangularis and to create awareness of Cissus quadrangularis among young adults. Methodology: This food product development study was informed by key informant interviews as well as a desktop study on food and nutrition trends. Through informed consent, ten elderly community members participated in the key informant interviews and shared their knowledge, uses and perceptions of Cissus quadrangularis. The developed food product underwent pilot and final sensory evaluation through a 9- point hedonic scale and a paired preference test. For the sensory evaluation, 110 participants were used, 10 for the pilot and 100 for the final sensory evaluation. The food product also underwent microbiological testing, nutrient analysis, and shelf-life testing. Once this was conducted, an awareness tool was developed. The awareness tool underwent pilot and final evaluation via a Likert scale. For the awareness tool survey, 110 young adult participants residing in KZN were used, 10 for the pilot and 100 for the final instrument. Results: Analysis from the key informant interviews indicated that the participants viewed Cissus quadrangularis as a medicinal plant, used to treat sprains, inflammations, broken bones, cholesterol, and ulcers. The participants cooked the plant in curries, pastes or fried doughs and some participants boiled it and drank the water. The desktop study on food and nutrition trends displayed key food trends for 2019 and 2020 such as zero-waste foods, botanical beverages, alternative ingredient, sustainability, plant-based foods, and natural remedies, less sugar, health convenience items, and texture. The results from the key informant interviews and desktop study on food and nutrition trends informed the development of the food product with Cissus quadrangularis. Following the steps of product development, a trendy energy bite infused with Cissus quadrangularis was developed. The energy bite yielded 10 portions of 21.5g each. Analysis from the microbial test indicate that the microbial count in the product was high averaging between 1000 to 5000 cfu/g which was within acceptable limit. However, the product was suitable for a short shelf-life of three days. Potassium sorbate was added to the energy bite infused with Cissus quadrangularis for the second microbial test. The second test results indicated that the microbial count found in the developed product was low and that there were no microorganisms present. The Cissus quadrangularis infused energy bite (both samples) indicated that the product was to some extent high in sugar (4g: 3.4g / 6g: 3.48g per 21.5g). The nutrient analysis showed that the product was relatively low in fat and sodium. The energy bite carbohydrate level was relatively low as it contributed (Women: 6.72 %/ Men: 6.32%) to the Dietary Reference Intake (DRIs) of women and men aged 19-30 years old. The amount of dietary fibre present in this study; in both samples was high (4g: 4.02 / 6g: 4.16 per 21.5g), contributing well to both women and men DRIs of dietary fibre, respectively (Women: 16.08 % / Men: 10.94%). The protein value in the energy bite was significantly low only contributing Women: 3.17% / Men: 2.6% to the DRIs of women and men, respectively. The vitamins and minerals tested in the nutrient analysis were not present in notable amounts, contributing low percentages to both women and men’s DRIs. Analysis from the pilot and final sensory evaluation showed that both the 4g and 6g sample of the developed food product was liked, however, the 4g sample was preferred. The final sensory evaluation showed that 27% of participants chose “like extremely” for the 4g sample whilst 18% of participants chose “like extremely” for the 6g sample. The Wilcoxon signed ranks test indicated that there was no significant difference between the 4g and 6g sensory rating score (p=0.066) indicating that there was a marginal preference of sample 1 (4g) over sample 2 (6g). There was no significant difference in the sensory rating of these products across gender for the 4g (p=0.521) and 6g (p=0.673) sample. The last objective of the study was to develop an awareness tool using the developed food product to create awareness of Cissus quadrangularis among young adults. The pilot and final awareness tool survey showed that the majority of participants found the awareness tool to be informative and that the participants involved were willing to make the recipes using Cissus quadrangularis. The final awareness tool results indicate that a significant 93% either liked or extremely enjoyed the video (p<.0005). Analysis with Pearson’s chi-square (Fisher’s exact test) of the cross-tabulation of responses with demographics shows that there was a significant relationship between gender and video rating, Fisher’s exact = 11.129, (p=.007). The results indicated that 57.1% of male participants extremely enjoyed the video whereas 59.3% of females only liked the video. Conclusion: The development of a trendy and sensorially acceptable food product with Cissus quadrangularis as a main ingredient and the development of an awareness tool created awareness to this unfamiliar indigenous plant with various health benefits among young people. Food product development using indigenous edible plants can be seen as sustainable measure and can contribute towards food security initiatives in South Africa. Awareness tools that appeal to the youth can help educate young adults on various indigenous foods reducing the vulnerability of food and nutrition insecurity.
Development of an electrochemical immunosensor for the detection of steviol glycosides by experimental and computational methods
(2020-04) Hloma, Phathisanani; Bisetty, Krishna; Sabela, M. I.; Kanchi, S.
An electrochemical immunosensor employs antibodies as a capture and detection mechanism to produce an electrical charge for the quantitative analysis of target molecules. The current analytical methods for the separation and detection of stevia glycosides can be tedious in terms of sample preparation and the lack of selectivity. However, electrochemical immunosensors provide selective, sensitive and costeffective detection routes for these widely consumed sweeteners. In this study, the author developed an electrochemical immunosensor for the detection and quantification of steviol glycosides, a non-nutritive sweetener widely employed in the food and beverage industries. Most of the artificial sweeteners are low-calorie sweeteners recommended for health-related illnesses. The stability of these sweeteners at even high temperatures has increased their applications in foodstuffs widely. Constant exposure to these sweeteners is somehow associated with health complications, as some are cancer-causing agents. Although there are no reports on stevia glycosides as a health risk sweetener, its widespread use in the food industry needs to be regulated. Herein, the developed immunosensor was achieved by fabricating the platinum electrodes with graphene oxide (GO) assimilated in Zinc Oxide nanoparticles (ZnONPs) with multiwalled carbon nanotubes (MWCNTs) and immobilized with the human sweet receptor subunit T1R2. The electrochemical detection of the natural sweetening compound, Rebaudioside A (Reb A) was evaluated qualitatively and quantitatively using cyclic and differential pulse voltammetry, respectively under optimised conditions in pH 11 borate buffer from -0.4 V to 0.8 V vs Ag/AgCl. The GO/MWCNT/ZnONPs nanocomposite was characterized using High-resolution Transmission Electron microscope (HR-TEM), Thermogravimetric Analysis (TGA), Attenuated Total Reflection Mode Fourier transform infrared (ATR-FTIR) and UV-VIS spectroscopy characterization techniques. Also, asymmetric flow-field-flow fractionation and centrifugal flow-field-flow fractionation equipped with a UV-vis and multi-angle angle light scattering detectors were used to separate and characterize the size distribution of the synthesised ZnO nanostructures. The field flow fractionation (FFF) is one of the efficient separation techniques known, and centrifugal flow fieldflow fractionation separates different particle sized nanoparticles by density, thus determining size variation within the synthesised batch. The results obtained using FFF were compared and validated with the conventional characterisation techniques described above. Computational studies were used to supplement experimental results using docking and adsorption methods. Adsorption studies were carried out to better understand the mechanistic aspects between T1R2, the nanocomposite used to modify the platinum working electrode, and the analyte Reb A. Docking studies between the T1R2 receptor and the steviol glycosides were used to explore the interaction and mechanism of the immunosensor detection. The results of this study may contribute to the development of an immunosensor that can potentially be used to quantify steviol glycosides in the food and beverage industry
Development of nutrition education material for caregivers of immune compromised children in children's homes in the Durban area
(2011) Grobbelaar, Hendrina Helena; Oldewage-Theron, Wilna; Napier, Carin E.
Nutrition plays a fundamental role in the care and support of people living with the Human Immunodeficiency Virus (HIV) and children in particular are affected by HIV and the Acquired Immunodeficiency Syndrome (AIDS) epidemic in Africa in various ways. The epidemic puts children at risk physically, psychologically and economically. Children are indirectly affected by HIV and AIDS when the epidemic has a negative impact on their communities and the services these communities provide. Undernutrition is a major problem in HIV-positive children in South Africa with severe malnutrition as a common finding in HIV-positive children. HIV contributes to an increased incidence and severity of undernutrition and micronutrient deficiency. Low serum levels of vitamins A, E, B6, B12 and C, betacarotene, selenium, zinc, copper and iron deficiencies are frequently documented during all stages of HIV-infection. Malnutrition in turn further weakens the immune system which increases the susceptibility to infections and the duration and the severity of infections. Thus, the immune response is less effective and less vigorous when an individual is undernourished. Although guidelines exist for the treatment and management of HIV-infected children, it is clear from the literature that exceptional measures are needed to ensure the health and well-being of the children are met. Furthermore, residential care should not only be considered as a last resort for children’s care, but also as an intervention that requires more than merely addressing children’s basic physical needs. Nutrition education has been utilised globally and in South Africa to address nutrition related problems. The main purpose of nutrition education is to provide individuals with adequate and accurate information, skills and motivation to buy, produce and consume the correct foods to stay healthy and lead an active life. Aim The purpose of this study was to develop reliable and valid nutrition education material for the child care workers (CCWs) of Immune Compromised children vi resident in Children’s Homes in the Durban area in order to maintain the child’s immune system and to optimise their quality of life. Methodology The FAO framework used for planning, implementing and evaluating a nutrition education programme was followed to develop the nutrition education material in this study. Phase I included a situational analysis of the children homes involved. The residential care settings that participated in this study included three Children’s Homes in Durban. The total purposive sample included: boys (5–19 years) n = 112, girls (5–19 years) n = 38 and CCWs n = 40. The sample of HIV-positive children included boys (5–19 years) n = 3 and girls (5– 19 years) n = 6. The physical measurements obtained for this study to determine nutritional status were weight and height. The anthropometric measurements were captured and analysed by the researcher using the World Health Organisation’s AnthroPlus version 1.0.2. Statistical software. The following indices were included: height-for-age (stunting), weight-for-age (underweight) and BMI-for-age (overweight and wasting). The WHO growth standards for school-aged children and adolescents were used to compare the anthropometric indicators. Dietary intake measurements were done by analysing the cycle menus by means of the Food Finder® Version 3 computer software program and comparing the results with the Dietary Reference Intakes (DRIs), specifically the EAR and AI where the EAR were not available. The data were analysed to determine the adequacy of energy and nutrient intake. Average portion sizes were established by the plate waste studies method as well as observation of practices, interviews with the central buyer and focus group discussions with the CCWs. Nutrition knowledge of the CCWs was determined by a self-administered questionnaire developed and tested for reliability and validity. The problems identified in Phase I through the implementation of the questionnaires and other methods directed the design of messages in Phase II. Once suitable media was selected, nutrition education material was developed based on existing guidelines pertaining to HIV and AIDS. The material developed was then tested for reliability and validity before it was produced. vii Results The anthropometric measurements indicated that the majority of the HIV-negative boys and girls were of normal height-for-age and weight-for-age. The results also showed that possible risk of overweight and overweight were more prevalent in girls whereas underweight was more prevalent in boys. Furthermore, the results indicated that a third (33.0%) of the HIV-positive children were stunted and 16.7% was severely stunted. Findings of the menu analysis indicated that both girls and boys consumed three times more carbohydrates than the recommended intake. The DRIs for girls and boys were met for energy and protein in all the age groups except boys aged 14-18 years did not meet the DRI for energy. However, the comparison of the actual intake of the macro nutrients with the WHO guidelines indicated that the protein (10.78%) and carbohydrate (58.07%) is within the recommendations of 10- 15% and 55–75% respectively. This comparison also showed that the total fat intake of 31.15% was above the recommended intake of 15-30%. None of the age groups met the DRIs for fibre. The comparison of the intake with the WHO guidelines also indicated that the total dietary fibre intake was only 19.67g/day and not 27–40g/day. The actual fruit and vegetable intake was a mere 68.64g/day instead of 400g/day as recommended. None of the groups met the DRIs for calcium and iodine. The results clearly showed that micro nutrient inadequacies were more prevalent in the dietary intake of age groups 9-13 and 14-18 years in both girls and boys. Inadequate intake of magnesium, vitamin A, vitamin C, riboflavin, niacin, vitamin B6, pantothenate, biotin, vitamin E and vitamin K were evident in the age group 14-18 year. Overall, it is evident from the results on nutrition knowledge that although the respondents’ knowledge was fair on general nutrition guidelines, the results of the nutrition knowledge questionnaire indicated that knowledge on the importance of a variety in the diet is lacking. The CCWs displayed a very poor knowledge of the recommended number of fruit and vegetable portions per day as well as correct serving sizes of vegetable portions. A very poor knowledge also existed regarding the role of healthy eating in maintaining and supporting the immune system and a limited knowledge on correct hygiene practices was noted. The fridge magnets developed included five messages relating to nutrition and four messages relating to food safety and hygiene. viii Conclusion This study established that malnutrition is apparent in the children’s homes and that there were many gaps in the nutrition knowledge of the CCWs. These gaps included the role of good nutrition in the support and maintenance of the immune system and the importance of adequate intake of fruit and vegetables daily. The NEM developed in this study will address these gaps.
Development of objectives for an educational programme to improve consumer knowledge of and attitudes towards nutritional information on food labels
(1994) Anderson, Diana Jane; Coertze, Dirk J.
Much attention has been given to the prevalence of diseases related to over-consumption of food, with nutritional labelling playing an increasingly prominent role in the prevention and reduction of these diseases. The development of technology and the subsequent availability of processed food have greatly contributed to these diseases, and created gaps in both distance and concept between the consumer and the manufacturer. An increasing number of food manufacturers are providing nutritional information regarding their products in order to maintain their position in the market; however, this avalanche of information is outstripping the ability of the consumer to use it effectively or to even comprehend it. This study was undertaken to identify the objectives needed for the formulation of an educational programme concerning the nutritional labelling of food containers.
Dietary diversity and nutritional status of pregnant women attending an ante-natal clinic in KZN
(2018) Warriner, Kelly Michelle; Napier, Carin E.; Grobbelaar, Hendrina Helena
Aim: This research aimed to establish the socio-demographic background, nutritional status, as well as food intake patterns of pregnant women in the first trimester of pregnancy attending an antenatal clinic in Cato Manor, Durban. This study formed part of the first phase of the MRC approved study “A multi-staged multi-disciplinary healthcare approach in reducing maternal morbidity and mortality rates in a selected district in KwaZulu-Natal”, aimed at pregnant women and planned by the Faculty of Health Sciences at the Durban University of Technology. The research was conducted in South Africa in the province of KwaZulu-Natal. This study was conducted in a primary health care clinic (PHC) in Cato Manor which falls under the auspices of the eThekwini municipality. The total sample (n=300) as predetermined by the MRC approved study included all pregnant women presenting at the PHC for their first antenatal visit over a designated period until the total sample size has been reached. These women were allocated into 3 groups: Group 1 compromised of the antenatal intervention group (n=100). A total of 139 pregnant women in the first trimester of pregnancy were eligible to be accepted to be a part of the study; however, due to a low return rate and incomplete questionnaires, a final sample of 100 women were included in the study and their data was used. Methods: A valid and relevant socio-demographic questionnaire was completed in a one-on-one interview situation wherein participants would be asked to tick relevant answers pertaining to the question at hand. Information regarding income, education level, religious influences and any other questions relating to the socio demographic background of the participants were included in the questionnaire. A valid and reliable food frequency questionnaire was also completed in a one-on-one interview situation whereby participants would be asked to tick relevant answers pertaining to the question at hand, in order to determine the food variety and food diversity intake of the participants. Participants’ dietary intake was determined through the completion of two x 24- hour recall questionnaires which were conducted in an interview situation. The two x 24-hour recall questionnaires were completed pertaining to the participant’s dietary intake during the week as well as to the participants’ dietary intake on a weekend day. Finally, participants’ anthropometric measurements were obtained through the use of a scale and stadiometer in order to measure the weight and height, respectively, of each participant and calculate the BMI (body Mass Index) of each participant. All measurements were conducted twice and the average of the two figures was used in order to ensure accuracy. Results: The majority of the participants’ role in the family was that of a daughter (72%) and they lived in a squatter camp (48%). In addition, 57% of participants shared a house with between two and five other people and the majority lived in a brick house (51%) with more than two rooms (63%). Most of the women were unemployed at the time of research (65%) and received a total monthly income of
The effect of seasonal food variety and dietary diversity on the nutritional status of a rural community in KZN
(2014-08-07) Nsele, Nelisiwe; Napier, Carin E.
Introduction: Dietary diversity is an indicator of access and measurement of household food security as it relates to income, location and seasonality. Dietary diversity is measured by physically counting the number of individual foods as well as food groups consumed over a given reference period. When dietary diversity is accurately measured, nutrient adequacy will be easily predicted. In order to measure dietary diversity accurately, it is important to determine household food security. Insufficient food and resources often result in food insecurity which leads to little or no dietary diversity. Poor populations suffer most from achieving dietary diversity because they consume a standard diet based on starchy staple food with limited fruits and vegetables resulting in multiple nutrient deficiencies. Rural communities rely on seasonal food variety in order to obtain fruits and vegetables needed by the body to limit nutrient deficiencies. Some seasons are more productive than others. Rural communities also use various coping strategies to deal with food insecurity in all four seasons. High levels of unemployment as well as a lack of nutrition education results in most rural households unable to cater for dietary diversity. Aim: The aim of the study is to determine the effect of seasonal food variety, dietary diversity and nutrient adequacy on the nutritional status of women in rural areas. Method: A hundred women in this community were weighed and measured and BMI determined and classified according to the WHO cut-off points for BMI. Waist circumference was measured in order to determine the waist-to-height ratio indication risk of metabolic syndrome. Twenty four hour recall questionnaires were used to determine actual intake compared to dietary reference intake (DRIs). Food Frequency Questionnaires for a period of seven days were completed captured and analysed using the SPSS version for descriptive statistics in order to determine food diversity. Coping strategies were determined by Focus Group interviews with community members in order to identify the various strategies used in time of food shortages. The severity of these strategies was determined by the community. Seasonal food consumption patterns and dietary intake behaviour were assessed over the four seasons. The highest frequency score (7) x severity weight (1-4) x10 strategies = maximum score of 140. Thus the higher the score the more food insecure the community is. Results: Food production from crops differs in different seasons. Food insecurity is high in summer and autumn due to a low number of food items harvested from crops. The community cope less in summer and autumn due to less crops available. The community is more food insecure in spring and winter due to the high number of food items harvested from crops. The community cope better in winter and spring due to the high level of available crops. Anthropometric measurements indicated that 41.2% of women between 31 and 50 and 49% of women between 51 and 70 years of age had a BMI of 30 and above. About 44% of total women are obese and 29% are pre obese. Only 26% had a normal weight. The 24 hour recall analysis indicates that the high level of obesity is due to the fact that a high number of participants consume large amount of carbohydrates every day. Conclusion: Overall results in this study indicated that this rural community is food insecure, on a higher level during summer and autumn, which leads to the consumption of undiversified diets. The women are malnourished and obese with a risk of metabolic syndrome. The information obtained in this study can be used to formulate strategies to develop interventions that can be used to access sufficient food in rural area in order to improve food insecurity, dietary diversity and, therefore, nutrient adequacy.
Electrochemical aptasensor for the detection of mycotoxins in food samples by experimental and computational methods
(2021) Kunene, Kwanele; Bisetty, Krishna; Kanchi, Suvardhan; Sabela, Myalowenkosi Innocent
Mycotoxins are secondary metabolites of fungi that are present in various foodstuff and feed commodities. A large number of mycotoxins exist, however only a limited number represent a major damages and toxic properties. Amongst them, the aflatoxins and ochratoxins are deemed to be the most poisonous and extensively circulated in the world and then, represent a real hazard to both human and animal. Depending on several factors like the consumption levels, exposure time, mechanisms of action, digestion and defense mechanisms, mycotoxins stimulate a wide spectrum of toxicological effects leading to both acute and chronic diseases, liver and kidney failure, skin rash, cancer, immune suppression, birth defects or even death. To address the harmful impact of mycotoxin contaminants in food and feed, health authorities in various countries world-wide have established guidelines in order to protect human and animal from the possible damages instigated by these toxins. Authorities such as the European Commission, US Food and Drug Administration (FDA), World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO) set up maximum level regulations for main mycotoxins in foods and feeds. To accomplish the expectations of these regulation levels, there is a great need for the development and validation of modern, uncomplicated, rapid, and detailed methodologies for the detection of toxins. In this study, various approaches for the rapid, inexpensive and ultrasensitive biosensors for the detection of two major mycotoxins were developed. The electrochemical-based aptasensor and immunosensor were developed for the determination of aflatoxin B1 (AFB1) and ochratoxin A (OTA) in different food products. The fabricated biosensors demonstrated good practical analytical feasibility for mycotoxins detection in real samples such as WeetBix, yoghurt, coffee and in wine samples with excellent recoveries and RSD values. To avoid fouling on the sensor surface by the constituents present in real samples, the carbon screen printed electrode (C-SPE) and carbon felt electrode (CFE) surfaces were modified with different nanomaterials such as silver nanoparticle (AgNPs), palladium nanoparticles (PdNPs), palladium doped boron nitride (PdNPs-BN) and titanium nanoparticles doped with boron nitride BN-TiO2. In addition, the aptamers and antibodies were immobilized on the modified electrode in order to enhance the selectivity of the sensor towards the detection of OTA and AFB1. The electrochemical aptasensor for OTA permitted for highly sensitive detection in Weet-Bix with a wide linear range (0.002 - 0.016 mg L-1) and limit of detection of 7×10-4 mg L-1. It is worth prominence that it is the first time that carbon screen printed electrode (C-SPE) modified with AgNPs was used, opening new pathways for highly precise analysis. Experimental results were further supported computationally for a better understanding of the interaction between the aptamer and the analytes. Computational results were in good agreement with experimental results. The same procedure was also established in voltammetric detection of AFB1 using CFE modified with BN-TiO2 (CF/BN-TiO2). A wide concentration range of 2.5 - 20 ng mL-1 with an excellent LOD of 0.002 ng mL-1 for AFB1 was obtained. For the case study of wine samples tested for AFB1 detection, a simple but very effective pretreatment method was effectively applied. The addition of acetonitrile to the wine reduces the non-specific interactions that might be accountable for inactivation of antibody and blocking of the sensor surface. Furthermore, the PdNPs-BN enhanced the electrical signal and the sensor sensitivity. Attained results allowed for AFB1 detection at concentrations range from 1.0 - 10 ng mL-1 with limit of detection of 0.832 ng mL-1 . In the case study of the electrochemical immunosensor for the detection of OTA in coffee, a linear detection range of 0.5 - 20 ng mL-1 was achieved with LOD of 0.096 ng mL-1 . The fabricated aptasensors and immunosensors in this study combines the most desirable characteristics of a good biosensor such as high sensitivity, inexpensive, rapid, and simple but portable method make proposed approaches an important and very promising tools for extensive biosensing applications.
Elemental determination of lubricating grease using ICP-OES
(2015) Marume, Cathrine; Govender, S.; Redhi, Gyanasivan Govindsamy
The focus of most lubricating grease testing has been based on performance and appearance rather than determining the concentration of chemical components. The primary reason being lubricating grease is a difficult matrix to work with from the perspective of the analytical laboratory. The purpose of this study was to develop a simple, reproducible method for elemental determination in lubricating grease and to apply the developed method to work out a flushing procedure for the filling lines in a grease manufacturing plant. The first part of the experimental work focused on developing a suitable and efficient sample preparation technique. Three techniques were explored: direct dilution, microwave assisted acid digestion and emulsification. Direct dilution involved shear mixing the lubricating grease with metal free base oil and diluting it with an organic solvent. Use of these solvents caused plasma destabilization or even plasma extinction and their use posed health risks for laboratory personnel. Microwave digestion involved mineralising the lubricating grease using an optimised microwave assisted acid digestion procedure. In the third sample preparation technique, microemulsions were formed by mixing the lubricating grease with a relatively small volume of a strong mineral acid mixture followed by the surfactant (triton X-100) at room temperature and pressure (RTP). This approach does not require the destruction of the organic matter or the use of large amounts of organic solvents. For all three techniques the sample was subsequently analysed for Al, B, Ba, Ca, Li, Na, S, Mo and Zn. All analysis was performed using an Optima ICP-OES with previously optimised parameters. The direct dilution method gave the most inconsistent results with relative standard deviation (RSD) as high as 56% for calcium, 79% for boron and 66% for lithium. Microwave digestion and emulsification gave comparable results, with the calibration curves of oil emulsions not differing significantly from aqueous ones. For microwave assisted acid digestion the limits of detection ranged from 0.028 mg/L for sodium to 0.255 mg/L for boron. Correlation coefficient values (r2) of all the elements were greater than 0.99. Likewise the limits of detection for emulsification ranged from 0.03 mg/L for aluminium to 0.37 mg/L for sulphur. The correlation coefficients for all the elements were greater than 0.99 and this indicates that the calibration curves were sufficient for analysing the digested grease samples. Five quality assurance samples were analysed using both methods and in addition a t-test performed at the 99.9% confidence level and 4 degrees of freedom showed that the two sample preparation techniques gave similar results. Emulsification has several advantages over microwave digestion technique and superior analytical performance over direct sample dilution using solvents, and hence was chosen as the method of choice for routine analysis of lubricating grease. The second part of the experimental work focused on developing a flushing procedure for filling lines in a lubricating grease plant. A flushing procedure is essential in order to minimise waste, which will in turn minimise production costs and avoids incurring disposal costs. In this series of experiments, the microwave digestion sample preparation technique was utilised for the subsequent determination of the flushing mass required in between product changes. The flushing procedure was implemented and monitored by the use of statistical quality control tools for a specified period of time, and as indicated by Shewart Control charts, the process was in statistical control.