Theses and dissertations (Applied Sciences)
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Item Non-nutritive sweeteners: consumer awareness, consumption and inclusion in food and beverage products in South Africa(2022-09) Naicker, Shakun; Naicker, Ashika; Singh, EvonneBackground: While there are several advantages that have promoted the consumption of non-nutritive sweeteners (NNSs) like aiding weight loss and supporting diabetes management, there are also concerns about potential negative side effects, such as cancer, insulin resistance, and compensatory appetite that overshadow their use. Globally, NNSs has become a steadfast ingredient in the reformulation of sugar sweetened beverages (SSBs), but more recently there has been a growing inclusion of NNSs in a wide variety of food items making this ingredient widespread across food categories available in South Africa (SA) due to its functional profile. Furthermore, a sugar tax levy was introduced in SA in 2018 as a counter measure to support the strategic health plan to reduce the country’s prevalence of noncommunicable diseases (NCDs) broadening the widespread usage of NNSs in food and beverage industry. Aim: The aim of the study is to investigate consumer awareness and consumption of NNSs in SA. This study further explores the widespread usage of NNSs through a sub-set of food and beverage products in the South African market. Methodology: The study used exploratory and quantitative methods to gather data for the research through a cross-sectional survey. The NNS consumer survey was administered to South African participants aged 18 years and older, to all races, men, and women. Convenience and snowball sampling methods was used to recruit 385 participants. The NNS consumer survey was adapted and developed from a study that assessed the knowledge and perceptions of NNSs in the (United Kingdom) UK population. At the beginning of the survey, the introductory paragraph described the background and the aim of the survey, a letter of information and ethical approval for the study was also provided. Sequentially, the questions were related to the participants general health, knowledge, and awareness of NNSs. The survey flowed into a regulatory section which give further insight into participants level of knowledge, perception, and trust of NNSs and concluded with a list of beverages, sweeteners and snacks products to determine consumer consumption thereof. The last section was the NNSs product consumption part of the survey where participants were presented with a list of products containing NNSs and were asked to indicate if they consumed these products. The questionnaire design and the reliability of the questionnaire was pilot tested prior to the survey administration among consumers that were excluded from the main study (n=10). The survey was disseminated through social networks, LinkedIn™, Facebook™ and WhatsApp™ and was designed on 2 different survey design platforms: Google Forms and Microsoft Forms. A scientific product database was established to determine the number of products that contain NNSs within specific categories which included snack foods, dairy products, sugar-free chewing gum, candy, sugar-sweetened beverages, energy drinks, diabetic products, and baby foods, found in three major South African retail stores: Checkers, Woolworths and Dis-Chem. The scientific product database also identified the type of NNSs used, singularly and different combination in products and health and wellness claims for all products examined. Results: The NNSs consumer survey was completed by 388 South African adults nationally. The survey was opened to all provinces in SA, but high participation came from Gauteng 31.4% (n=122), and KwaZulu-Natal 29.6% (n=122), followed closely by 19.8% (n=77) from Western Cape. Women participants dominated the survey with a weighted 66.5% (n= 258) of the responses, followed by 33.5% (n=130) of the responses received from men. All races participated in the survey with most responses from Black participants (40.2% n=156), followed by Indian/Asian (30.2% n=117), White (18.0% n=70) and Coloured participants (11.6% n=45). Results showed that mainly the younger South African population with 24.2% (n=94) aged 18-24, 27.6% (n= 107) aged 25-34 and 24.7% (n=96) aged between 35-44 took part in the survey. Participants were asked to indicate if they had any NCDs and the prevalence of the common three NCDs noted were high blood pressure 13.1% (n=51), type 2 diabetes 9.3% (n=36), heart disease 5.4% (n=21) and cancer 2.1% (n=8). A large percentage of participants reported no prevalence of NCDs 73.7% (n=286). Participants were then probed to identify from a list of sweeteners that was provided and indicate which sweeteners they heard off. Interestingly, the results indicated that a large proportion of the participants did not hear of NNSs like neotame 94% (n=363), acesulfame-K 92% (n=356), malitol 84% (n=324), stevia 65% (n=253), saccharin 59% (n=227) and sucralose 59% (n=229) however, a significant 61% (n=238) of participants have heard of xylitol, p<.001 and 45% (174) have heard of aspartame. A total of 33.5% (n=130) p<.001 participants indicated that they consumed products labelled “sugar-free” or “diet” either ‘never’, ‘less often than once a week’ or ‘a few times a week’, p<.001. The relevance of this result is that although a significant 33.5% (n=130) p<.001 of participants consumed products labelled ‘sugar-free’ and/or ‘diet’, they may not actually know the ingredient contained in these products that qualifies it is as ‘sugar-free’ and/or ‘diet’ contain. Participants were given a list of products to select from and were requested to state which products they consume that they think may contain NNSs. A significant 68.3% (n=265) (p<.001) of participants indicated that they consumed cool drinks that they think contain NNSs whilst a significant 71.4% (n=277) (p<.001) did not consume cakes and desserts with NNSs, 70.1% (n=272) did not consume tea, coffee and hot beverages with NNSs and 63.7% (n=247) did not consume chewing gum that contain NNSs. Regarding the use of NNSs in everyday routine, a significant 68.3% (n=265) participants reported that they did not knowingly use NNSs in their everyday routine (p<0.001). The results from the survey further indicated that 50.8% (n=197) of participants were aware of health concerns related to the consumption of NNSs which represents just over half of the participants view. The result for these three statements – ‘I think calling them "artificial" makes me sceptical about their safety’(p=0.00), ‘I worry about the effects that non-nutritive sweeteners can have on my body’ (p=0.00), ‘I have concerns about non-nutritive sweeteners and the risk of cancer’ (p=0.00), was significantly agreed with. There was significant agreement on these benefit statements – ‘non-nutritive sweeteners are helpful for someone who wishes to lose weight’ (p=0.00), ‘non-nutritive sweeteners allow for a little indulgence without feelings of guilt’ (p=0.00), ‘non-nutritive sweeteners allow for diet products to be a viable option’ (p=0.00). When participants were probed on trusting information on health and wellness, the results presented that a significant 55.36% (p=0.00) of participants do not trust the information from government health agencies, regulatory bodies and the information coming from the Department of Health (DOH p=0.00). The results also presented that there was a significant agreement (M=3.11) that NNSs are not good for one’s health, (p=.020). Finally, a list of products consisting of beverages, sweeteners and snack products was provided, and participants were requested to indicate which products they consume. The list of products that was presented to participants in the survey were a mix of products where some were most likely to contain NNSs and some were not, like smoothies, chocolate bars and cakes. The data presented that a significant 92% (n=356) (<.001) consume hot beverages (tea, coffee, hot chocolate), 76% (n=294) consume fruit juice and concentrates, 55% (n=213) said yes to milkshake and 54% (n=208) consume diet cool drink. Interestingly, 68.3% (n=265) of participants that said no to knowingly using NNSs in their everyday routine said yes to consuming beverages that may contain NNSs. Of these 68.3% (n=265), 77.2% (n=95) consume fruit juice and concentrates, iced tea, 73.2% (n=90) consume diet cool drinks, 64.2 % (n=79) consume flavoured sparkling water, 55.3% (n=66) consume milkshakes, 53.7% (n=66) consume energy drinks and 40.7% (n=50) consume protein drinks. Participants also indicated their passion for snacking when they were asked to indicate which snacks they consumed. A significant 81% (n=351) consume crisps, 85% (n=330) consume biscuits/rusks, 87% (n=339) consume chocolate bars, 82% consume (n=320) cakes and 82% (n=319) consume ice-creams. A scientific product database consisting of 419 products that contain NNSs was established. These ranged from snack food, dairy, confectionary, SSBs, energy drinks and diabetic products. The data presented that the highest product category containing NNSs were snacks which made up 45% (n=186) and this was followed by the SSBs category with 21% (n=91) that contained NNSs. The snack food category was made up of the following subcategories: desserts 30% (n=55), crisps 26% (n=48), biscuits 23% (n=43), cereal 9.6% (n=18), sauces 6% (n=12), energy bars 4% (n=7), frozen snacks 1% (n=2) and popcorn 0.53% (n=1). From the NNSs and consumer survey, the results demonstrated that snacks were the highest and most popular consumed products with 81% (n=315) consuming just crisps. From the 419 products that were examined, 65% (n=273) products contained a combination of NNSs used to formulate the product and 34% (n=146) products consisted of single NNS. An interesting outcome that was noted here was that sucralose was most common in formulations where it was found in 38% (n=55) products followed by sorbitol in 16% (n=24) and stevia in 16% (n=23) of the products. Data presented that xylitol was not used individually in products examined. Conclusion: The outcome of this research has highlighted key consumer insights, presenting sound data that brings to light the current consumer position on the topic of NNSs and its broad use in products in SA. The data highlighted the education gap confirming the initial assumption that there is a high probability that many South African consumers are consuming NNSs without being aware of it. This research has created so many opportunities to improve consumer knowledge and investigate if there is a need to enforce stricter formulating measures with NNSs based on the evidence obtained through the NNSs survey and the scientific product database. These findings should be used to challenge manufacturers, the governmental guardians within the Department of Health and regulators in SA to guide consumer knowledge, awareness, perception and trust. There is a much bigger responsibility and significant role to play in protecting, sustaining, and investing in consumer health and wellbeing, with a priority to focus on consumer education.Item Electrochemical enzymatic biosensing of neotame in sweeteners by experimental and computational methods(2020) Lephalala, Matshidiso; Bisetty, Krishna; Kanchi, Suvardhan; Sabela, Myalowenkosi I.An enzymatic biosensor comprises of an enzyme, which recognizes and then reacts with the target analyte producing a chemical signal. In this type of sensor, an electrode is a key component that is employed as a solid support for the immobilization of biomolecules and electron movement. This work focuses on two case studies to assess the signal enhancing strategy that can potentially be used to quantify Neotame (NTM) in food and non-alcoholic beverages. The first case study involves a highly sensitive electrochemical enzymatic biosensor for the detection of NTM in the soft drinks developed, based on multiwalled carbon nanotubes (MWCNTs) decorated with aloe vera-derived gold nanoparticles (AuNPs) and carboxylesterase (CaE) enzyme. This electrochemical biosensor showed high sensitivity with a limit of detection (LOD) and limit of quantification (LOQ) of 27 μg L-1 and 83 μg L-1, respectively. The calibration plot revealed a linear dependence of the cathodic peak current on the NTM concentration profile with anR2 of 0.9829, indicating an improved electrocatalytic property of the glassy carbon electrode. The viability of the proposed strategy was confirmed by assessing the interactions between the enzyme and the analyte using computational methods. The density functional theory (DFT) calculations of NTM showed a HOMO–LUMO energy gap of -0.46618 eV, indicating that NTM can act as a good electron donor. Moreover, adsorption and enzyme-analyte docking studies were carried out to better understand the redox mechanism. These outcomes showed that NTM formed hydrogen bonds with LEU 249, GLU251, and other amino acids of the hydrophobic channel of the binding sites, making it easier for the redox reaction to take place for the detection of NTM. The results confirmed that the aloe vera-derived AuNPs are good platforms for immobilizing CaE because of their high surface area, encouraging an electron transfer from NTM to form a substrate-enzyme complex, contributing to improved biosensing signals. The second case study deals with an enzymatic biosensor developed, based on graphene oxide (GO) anchored with honey-derived nickel nanoparticles (NiNPs) and alcohol oxidase (AOx) enzyme. The biosensor showed high sensitivity with a limit of quantification (LOQ) of 47 μg L-1 and a limit of detection (LOD) of 15 μg L-1, respectively. The calibration curve of the cathodic peak current on the analyte concentration profile showed an improved electrocatalytic property with an R2 of 0.9926. The interactions between the enzyme and analyte were assessed using computational tools to confirm the viability of the proposed biosensor. A HOMO– LUMO energy gap of -0.46618 eV was confirmed using density functional theory (DFT) calculations, this suggested that NTM has great potential to act as an electron donor. Analyte-enzyme and adsorption docking studies were carried out for a better comprehension of the redox reaction mechanisms. These outcomes indicated that NTM forms hydrogen bonds with TRP 47, ARG 56, VAL 328, PRO 55, and other amino acids, thus assisting the redox reaction for the determination of NTM. The results confirmed that the honey-derived NiNPs have a high surface area, which acted as a good platform to immobilize AOx so that the electrons can be transferred from NTM to form a substrate-enzyme composite to give out an improved biosensing signal. Moreover, the magnified catalytic activity of these two biosensors for the determination of NTM in soft drinks showed great potential in the beverage industry.Item Development of electrophoretic and biosensor methods applied to high intensity sweeteners(2015) Bathinapatla, Ayyappa; Dovey, M.; Bisetty, KrishnaMaterials which show sweetness are classified as nutritive sweeteners and non-nutritive sweeteners or artificial sweeteners. In the present work, capillary electrophoresis and electrochemical biosensors have been used to analyse and quantify the natural and chemical artificial sweeteners in different food samples. The experimental work was further supported by computational studies. Capillary electrophoresis (CE) is a technique in which charged molecules can efficiently be separated in a buffer solution within a capillary tube under the influence of a strong electric field. While in the case of a biosensor, the analyte interacts with the bioreceptor and the resulting output is measured by a specially designed transducer. Steviol glycosides (rebaudioside A and stevioside) are natural sweeteners, extracted from Stevia rebaudiana Bertoni belonging to the Asteraceae family. On the other hand, neotame and sucralose are chemical sweeteners manufactured from their structural analogues aspartame and sucrose, respectively. Accordingly in this work, two CE modes, namely electro kinetic chromatography–capillary electrophoresis (EKC–CE) and an indirect UV-Capillary zone electrophoresis were used for the evaluation of analytes studied. Steviol glycosides (rebaudioside A and stevioside) and neotame diastereomers (L,L and D,D) were analysed using EKC-CE in the presence of a chiral separating agent β-cyclodextrin (TM-β-CD). However, since sucralose demonstrates chromophore-like properties, an indirect UV-CZE method was therefore developed using simple amines (morpholine, piperidine, ethylamine and triethylamine) as the background electrolytes (BGE). The optimum separation conditions in EKC-CE were; UV detection at 210 nm, 50 mM phosphate buffer, 30 mM TM-β-CD, 20 kV applied voltage, 5 s hydrodynamic injection and pH of 8.0 and 5.5 (for steviol glycosides and neotame), respectively. On the other hand, optimum separation conditions for the indirect UV-CZE method were; UV detection at 230 nm, 0.2 M morpholine buffer at pH 12.0, +20 kV applied voltage, 30 0C cassette temperature and 6 s sample injection. Furthermore, a highly sensitive and novel electrochemical biosensor was developed using platinum and glassy carbon electrodes fabricated with different nanomaterials. Accordingly, cytochrome c/graphene oxide – gold NPs/multiwalled carbon nanotubes (MWCNTs) modified platinum electrodes were used for the analysis of rebaudioside A. Similarly, copper NPs capped with ammonium piperidine dithiocarbamate-MWCNTs-β-cyclodextrin and laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) immobilized graphene oxide-p-aminothiophenol capped ZnO NPs nanocomposites modified with glassy carbon electrodes were developed for the determination of neotame and sucralose, respectively. The electrochemical behaviour of these sweeteners towards the developed sensors was tested by using cyclic voltammetry and differential pulse voltammetry under optimum experimental conditions (pH, scan rate, accumulation time, accumulation potential, pulse amplitude, voltage step and voltage step time). The prepared nanocomposites were characterized using thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It was found that the developed electrochemical biosensors showed excellent catalytic activity towards the determination of natural and chemical sweeteners in commercially available food samples. Additionally, a comparative study between capillary electrophoresis and biosensor methods revealed that at optimum experimental conditions, typical detection limits ranging from 0.02017 to 0.07386 mM for steviol glycosides, 0.01857 to 0.08214 mM for neotame diastereomers and for sucralose 0.2804 mM were achieved. In contrast to CE methods, biosensor methods attained very low detection limits of 0.264 µM, 0.013 mM and 0.325 µM for rebaudioside A, neotame and sucralose, respectively. The unique properties of the nanomaterials in combination with electro chemical techniques provided best results with shorter analysis time in contrast to the conventional separation methods. Finally, the computational molecular modelling tools were used to better understand the results obtained from the separation mechanisms using capillary electrophoresis. The interaction of β-cyclodextrin with steviol glycosides/neotame diastereomers and sucralose with the amine buffers were studied and the computational results were in good agreement with the elution orders observed in capillary electrophoresis. Furthermore, docking studies were performed to predict the binding affinity interactions between the artificial sweeteners and biomolecules (cytochrome c and laccase) to understand a molecular level.