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Theses and dissertations (Applied Sciences)

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    Effect of pectin and emulsifiers on quality and stability of wheat composite bread
    (2018) Ajibade, Betty Olusola; Ijabadeniyi, Oluwatosin Ademola
    Fortification and supplementation of wheat flour with other flour sources containing essential amino acids such as lysine, for bread production could help overcome the problem of protein- energy malnutrition. Indigenous and largely underutilised crops such as millet and bambara groundnut could be incorporated into staple foods such as bread. In this study, the rheological behaviour and quality characteristics of dough and bread made from wheat-millet-bambara flour (WMB) containing mixtures of emulsifiers and apple pectin were investigated for their suitability in breadmaking. WMB was prepared by substituting wheat flour (WF) with 25% each of millet flour (MF) and bambara flour. Pectin was added (1.0-2.0 g/100 g flour) and emulsifiers namely sodium stearoyl lactylate (SSL) (0.25-0.4 g/100 g flour), polysorbate 80 (PS80) (0.5-0.8 g/100 g flour), and diacetyl tartaric acid ester of monoglycerides (DATEM) (0.1-0.25 g/100 g flour) were mixed and added in different proportions. A Mixolab was used to measure the rheological behaviour of dough. The resulting bread was analysed for physical characteristics, nutritional composition, and organoleptic properties. Bread samples were stored at room temperature (±25℃), refrigeration (4℃) and freezing (-18℃) for 7 days. The bread samples were then investigated for firmness, compression energy, colour, visual observation of mould growth (VO), total aerobic plate count (APC) and fungal counts (FC). From the Mixolab analysis of composite dough, a significant increase (p<0.05) in the dough development time and dough stability were observed. The loaf volume, specific volume and proximate composition of the composite bread increased significantly (p<0.05) relative to the control. The protein content (33%), protein digestibility (85%) and some essential amino acids (lysine: 54.6%; threonine: 36.4%) increased significantly (p<0.05) compared to wheat bread (control) WF. Sensory evaluation revealed above-average acceptability for composite bread. Also, the pectin-treated bread (PTB) was significantly different (p<0.05) in firmness (8.47 N) compared to wheat flour bread (WF) (10.33 N) at -18℃ after 7 days of storage. The WF had the lowest firmness (8.32 N) at room temperature (±25℃) storage lower than the PTB (9.25 N) and emulsifier-treated bread (ETB) (12.37 N) after 3 days storage at room temperature (±25℃). Bread firmness decreased significantly (p<0.05) with an increase in storage time for all samples. The APC for all bread samples ranged from 3.02 log cfu/g to 6.19 log cfu/g and fungal count (FC) ranged from 3.48 log cfu/g to 4.86 log cfu/g. The PTB had the highest APC (6.19 log cfu/g) among bread samples stored at room temperature (±25℃) while it also had the lowest APC (3.02 log cfu/g) at the same storage temperature (±25℃). It was found that all bread samples stored at -18℃ did not show no sign of mould growth. The use of bakery products’ acceptable limits of emulsifiers and pectin for this study significantly improved the dough rheology, physical characteristics, nutritional and sensory acceptability of WMB composite bread. The shelf life studies showed improved firmness, low microbial counts and a slower rate of degradation in cold storage conditions. This study revealed that there is potential for supplementation and fortification of wheat bread with flours from millet and bambara sources.
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    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.
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    Dietary modulation of the human colonic microbiota through plant-derived prebiotic compounds
    (2007) Kassim, Muhammad Arshad
    The human gut microbiota play a major role in host health, and attempts are being made to manipulate the composition of the gut microbiota-increase the composition of bacterial groups, such as lactobacilli and bifidobacteria that are perceived as exerting health promoting properties. These bacteria defined as food supplements (probiotics) beneficially affect the host by improving the intestinal microbial balance, and have been used to change the composition of the colonic microbiota. However, such changes may be transient, and the implantation of exogenous bacteria therefore becomes limited. In contrast, prebiotics are naturally occurring carbohydrates that are classified as non-digestible oligosaccharides present in edible plants. These carbohydrates enter the colon as intact compounds, elicit systemic physiological functions and act as fermentable substrates for colonic microflora-influencing the species composition and metabolic characteristics of intestinal microflora providing important health attributes. Currently, a widely marketed prebiotic, inulin is extracted from plants of the family Asteraceae. There are many unexploited plants that are regularly consumed and that may have a prebiotic effect or can have very high levels of inulin which could make them commercially viable. In this study, we investigated prebiotic compounds, especially inulin from locally growing, non-commercialised leafy plants. The aqueous extracts of 22 plants from the families Asparagaceae, Alliaceae, Asteraceae, Solanaceae, Cucurbitaceae, Amaranthaceae, Acanthaceae, Polygonaceae, Portulaceae, Fabaceae, Chenopodiaceae, Pedaliaceae and Apiaceae from Kwa-Zulu Natal were investigated for a prebiotic effect using a modified batch-culture technique with Lactobacillus bulgaricus, Lactobacillus lactis, Lactobacillus reuteri and Bifidobacterium longum, four common probiotics and the inulin content of the plants was determined using high performance liquid chromatography. Of the 22 plants studied, Solanum nigrum, Amaranthus spinosus, Amaranthus hybridus, Asystasia gangetica, Senna occidentalis, Cerathoteca triloba, Asparagus sprengeri, Tulbaghia violacea, Sonchus oleraceus and Taraxacum officinale exhibited a prebiotic effect. The prebiotic effect of the Taraxacum officinale, Sonchus oleraceus and Asparagus sprengeri extracts on L. lactis and L. reuteri was higher than or equivalent to inulin-a commercial prebiotic. In this study, Sonchus oleraceus exhibited the best prebiotic effect-was the only plant to stimulate all the probiotics including B. longum. Of all the plants analysed, Asparagus sprengeri tuber contained the highest amount of inulin (3.55%).