Department of Food Science

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The addition of rooibos tea extract (Aspalathus Linearis) as a natural antioxidant to South African Droëwors
(Stellenbosch : Stellenbosch University, 2013-12) Jones, Maxine; Hoffman, Louwrens C.; Muller, M.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: The effect of rooibos tea (Aspalathus linearis) extract (RBTE) as a natural antioxidant on the lipid and protein stability and sensory profile of traditional South African droëwors (dried sausage) was investigated. Ostrich meat (Struthio camelus) and pork back fat was used in the initial study as the meat and fat sources. Four treatments were prepared with each treatment increasing in concentration of RBTE: RBTE 0%, RBTE 0.25%, RBTE 0.50% and RBTE 1.0%. The lipid stability of the droëwors increased after drying with RBTE 0.25% having lower TBARS than the other treatments. The protein stability and heme-iron results of the droëwors did not differ (P > 0.05) between treatments. The second study investigated the effect of added RBTE to droëwors of three different game species namely, blesbok (Damaliscus pygargus phillipsi), springbok (Antidorcas marsupialis) and fallow deer (Dama dama). No significant effects (P > 0.05) were seen between treatments in terms of the lipid and protein oxidation of the dried product within a species. Protein oxidation increased after drying but did not differ (P > 0.05) between the treatments within a stage (raw or dried) within species. Using different meat sources to the initial study and a shorter drying period did not result in any differences between treatments however, RBTE 0.25% did give the best results for lipid stability after drying. Heme-iron concentration differed (P < 0.05) between the RBTE treatments within the dried stage within a species with RBTE concentrations being inversely correlated with the levels of heme-iron. The final study investigated the addition of RBTE to blesbok and springbok droëwors using an improved formulation, drying parameters and a different (beef) fat source. The results indicated that RBTE 1.0% significantly (P < 0.05) slowed down lipid oxidation after a two week storage. The added RBTE, however, did not result in any significant differences (P > 0.05) in protein oxidation and heme-iron concentration. A positive correlation between lipid oxidation and heme-iron concentration was noted. Throughout the study the proximate composition analyses gave consistent results with the drying procedures. When the total moisture content decreased after drying, the fat and protein content became more concentrated. There were no differences (P > 0.05) between the moisture, protein and fat contents between treatments within a specific stage. High concentrations of oleic acid, stearic acid, linoleic acid and palmitic acid were detected. The fatty acid profile suggests that after drying there is a decrease in polyunsaturated fats which could explain the increase in lipid oxidation. With the addition of RBTE, differences in sensory attributes between the different droëwors treatments were detected by a trained panel. From these results it can be concluded that RBTE can be marketed as a natural antioxidant for use in droëwors. The composition of the RBTE particularly as pertaining to the levels of aspalathin and quercetin should however be considered when evaluating the level of RBTE to use.
Adoption of ICT by sheep farmers in the Western Cape (Karoo and Eden): towards sustainable farming
(Stellenbosch : Stellenbosch University, 2021-04) Mucheri, Vimbai; Molotsi, Annelin H.; Kirsten, Johann; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
Thesis (MScFoodSc)--Stellenbosch University, 2021.
Advances in design and performance evaluation of fresh fruit ventilated distribution packaging : a review
(Publishers version, 2020-02-17) Mukama, Matia; Ambaw, Alemayehu; Opara, Umezuruike Linus
This review was initiated to realise the state-of-the art in optimising the ventilation and structural requirements of corrugated packaging carton design. Researchers have been using computational methods: computational fluid dynamics, particularly, the finite volume method, to analyse the airflow and heat transfer performances, and computational structural dynamics, particularly, the finite element method, to analyse the loss of compression strength due to vent-holes. Models are validated using actual testing: wind tunnel based forced air cooling system to study the produce cooling kinetics and box compression test machine for the package industry to study the structural dynamics. Studies on the rate and uniformity of produce cooling and the loss of structural strength in corrugated cartons as a function of size, shape, and location of vent-holes are reviewed. Based on experimental data, results show that the loss in strength can range between 10–40 % on addition of vent and hand holes on cartons, and reasonable increase in cooling rates is only achieved with increase in carton face ventilation area only up to 7–8 %. With regards to internal packaging components, increasing awareness of consumers to the environmental degradation of especially disposable plastic packaging means packers and suppliers must devise means to cut back and eventually eliminate plastic packaging from fruit and vegetables.
Anaerobic bioconversion of liquid and solid wastes from the winemaking process
(Stellenbosch : Stellenbosch University, 2015-02) De Kock, Michelle; Sigge, G. O.; Britz, T. J.; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: South Africa is a developing country that relies on its agricultural sector as a main source of overall economic welfare. Development does not only give rise to new technology and new products but also results in increased amounts of liquid and solid waste. Generally, the production of wine is considered an environmentally friendly process, but significant amounts of natural resources and organic amendments are necessary, while generating large amounts of liquid and solid wastes. Anaerobic digestion (AD) is an attractive and proven treatment option for both liquid and solid wastes as valuable products and depollution can be obtained. AD of liquid waste results in an effluent and biogas, while anaerobic composting of solid waste results in an organic amendment, leachate and biogas. The overall objective of this study was to investigate the operational feasibility of the cotreatment of leachate produced during the anaerobic composting (AnC) of grape skins in an upflow anaerobic sludge blanket (UASB) reactor while treating winery wastewater. This first aim of this study was to investigate the efficiency of the anaerobic composting of grape skins. Laboratoryscaled digesters (1L) were utilised as anaerobic composting units. The most important operational parameters were identified (pH, moisture content and inoculum (size, ratio, composition)) in order to produce a pH stable, odour free compost in 21 days. Experimental studies highlighted the importance of shredding waste as well as the addition of calcium oxide and green waste to increase the initial pH of the composting mixture. After optimising a 50% (m.m-1) cow manure inoculum, lower inoculum concentrations (10, 15 and 25% (m.m-1)) were investigated to make the process more economically viable. A 10% (m.m-1) anaerobic compost (AC) inoculum was found to produce the most favourable results in terms of pH stabilisation and leachate generation. A 50% (m.m-1) moisture level performed the best by attaining a pH > 6.5 on day 6 and having the highest end pH (7.65) on day 21, while white and red grape skins in an equal ratio were found to generate a higher end pH. With all these optimum parameters in place (shredded waste, green waste, CaO, inoculum, moisture, grape skins), a compost with a final pH (7.09), moisture (58%), nitrogen (2.25%), phosphorous (0.22%) and potassium content (1.7%) was obtained. The optimised parameters were scaled-up (1:10) by using polyvinyl chloride anaerobic digesters (20 L) to suit the operational requirements of the AnC process and also produced a stable compost within 21 days. The second aim of this study was to investigate the combined anaerobic digestion of winery wastewater (WWW) and leachate obtained from the anaerobic composting of grape skins in an upflow anaerobic sludge blanket (UASB). This involved the operation of a 2.3 L laboratory-scale UASB reactor for 205 days. The reactor successfully co-treated WWW and leachate at ca. 8.5 kgCOD.m-3d-1 with a final chemical oxygen demand (COD) reduction of over 90%, a stable reactor effluent pH (7.61) and alkalinity (3 281 CaCO3 mg.L-1). This study showed the feasibility for the combined treatment of liquid and solid waste from the winemaking process. Although the legal limits for reactor effluent disposal onto land was not met, significant reduction in COD concentrations were achieved, whilst producing a soil amendment that could potentially result in cost savings for chemical fertilisers. The benefits related to using anaerobic bioconversion as a treatment option for liquid and solid waste could possibly be advantageous to the wine industry as an environmental control technology, by converting liquid and solid waste into valuable resources.
Anaerobic bioconversion of the organic fraction from the fruit processing industry
(Stellenbosch : Stellenbosch University, 2002-12) Griessel, Wilmare; Britz, T. J.; Fourie, P. C.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: South Africa is a developing country that relies heavily on its agricultural sector for economical welfare especially in the Western Cape Province. However, development gives rise to new technologies, new products, economical stability and unfortunately also to the production of larger volumes of liquid and solid waste. Anaerobic composting is becoming a very attractive treatment option for solid waste disposal because of its unique operational advantages and two valueadded by-products, compost and biogas. Over the last decade progress has been made in anaerobic digestion of solid wastes, but no literature could be found on the anaerobic composting of apple and peach pomace. The main objective of this study was to develop a method to anaerobically compost apple and peach pomace. In the first phase important operational parameters were identified and a method was developed to optimise the parameters. In the second phase of the study, the scaling-up and optimisation of the process were the major objectives. During the first phase of this research 2 L modified glass containers were used as composting units. The most important operational parameters (leachate pH, inoculum source and size, and initial moisture levels) were identified. Anaerobic compost from previous tests, brewery granules and anaerobic sludge were also used as inocula and evaluated for the best source of microbes. After optimising all the identified parameters, good results were obtained, which included higher biogas production, good volume reductions, less bad aromas and a compost product with a neutral pH. After developing the 2 L laboratory-scale method to compost the apple pomace anaerobically, the next step was to ascertain if the method would work if larger volumes of solid fruit waste were composted. A special 20 L composting unit made of PVC was designed to suit the operational requirements of the anaerobic composting process. It was also decided to mix apple pomace and peach pulp together and to use this solid waste source as part of the composting substrate. Different inocula, including cattle manure, anaerobic sludge, brewery granules and anaerobic compost produced in the previous tests, were used. Although good results were obtained with the anaerobic compost and cattle manure as inoculum, the aim was also to decrease the composting period by shortening the pH stabilisation period. To achieve this, it was decided to add NaHC03 to the substrate to be composted to facilitate a faster pH stabilisation. The composting period was subsequently shortened to 25 days with satisfactory results, which included a volume reduction, biogas production and faster pH stabilisation. An upflow anaerobic sludge blanket (UASB) bioreactor was also used to assist the composting process by facilitating the removal of the VFA's present in the composting leachate. This proved to be a valuable addition to the composting process as the UASB bioreactor also provided the composting units with a 'moisturising liquid', which was 'enriched' with a consortium of active anaerobic bacteria when the effluent from the bioreactor was re-added to the composting units. With all the operational parameters in place, good results were obtained and these included a volume reduction of 60% (m/m), a good biogas production, a composting period of only 25 days, a compost that was free of bad aromas, a final compost pH of > 6.5, final leachate COD values of less than 3 000 rnq.l", and a final leachate VFA's concentration of between 0 and 250 rnq.l". If in future research further scaling-up is to be considered, it is recommended that the composting unit be coupled directly to the UASB bioreactor, thus making the process continuous and more practical to operate. If the operational period of the anaerobic composting set-up could be further shortened and the inoculum adapted so that the process could be used for the treatment of other difficult types of solid wastes, it would probably be advantageous for the fruit processing industry to use this method as an environmental control technology.
Anti-microbial activity of rooibos tea (Aspalathus linearis) on food spoilage organisms and potenial pathogens
(Stellenbosch : Stellenbosch University, 2001-12) Schepers, Sonette; Britz, T. J.; Witthuhn, R. C.; Joubert, E.; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT:Aspalafhus linearis is an indigenous fynbos plant cultivated in the Clanwilliam area of the Western Cape, South Africa. The rooibos tea that is prepared from this plant, has become popular worldwide mainly due to the alleged health properties. Studies on the anti-microbial properties of green, black and oolong teas have shown that these teas have strong anti-microbial activity against a wide range of microbes. No studies have been done on the anti-microbial activity of rooibos tea and the aim of this study was to determine what impact rooibos tea extracts would have on the growth of different food spoilage and potential pathogenic microbes. Water and ethyl acetate extracts of fermented and unfermented rooibos tea were used to determine the inhibitory effect on the growth of an Escherichia coli strain. The E. coli culture was grown in tea-MRS with either added fermented or unfermented rooibos tea extracts. Both the water and ethyl acetate extracts showed a strong inhibitory effect against the E. coli strain in that there was a decrease in the final bacterial cell density (Nmax)(from 0.59 00 to 0.25 00) and the maximum specific growth rate (~max)(from 1.12 h-1 to 0.20 h-1) and an increase in the doubling time (~) (from 0.59 h to 1.80 h) and lag time (tlag)(from 4.81 h to 6.60 h) as the concentration of the soluble solids of the tea extracts was increased from 0.5 to 5.0 g.r1 . Furthermore, it was found that the fermented rooibos tea had a much stronger inhibitory effect (69% decrease in growth at 5.0 g.r1 soluble solids) compared to the unfermented rooibos tea extracts (35.1% decrease in growth at 5.0 g.r1 soluble solids). The resulting data indicated that rooibos tea had a very strong inhibitory effect on the growth of the E. coli strain. It was also found that the water extracts of rooibos tea showed a stronger inhibitory effect on the growth of the E. coli than the ethyl acetate extracts, indicating that the antimicrobial activity of rooibos tea is not exclusively due to the polyphenolic content - individual compounds. It was also determined that the rooibos tea water extracts showed a bacteriostatic action against the E. coli strain in that as soon as the tea is no longer part of the growth medium, the E. coli resumed a normal growth pattern. The data obtained showed that the inhibitory effect of rooibos tea water extracts (69% decrease in growth) against the growth of E. coli was more pronounced than that found when black tea water extracts (25.7% decrease in growth) at the same concentrations were used.Rooibos tea water extracts (0.5 - 5.0 g.r1) of fermented and unfermented tea were also used to determine the inhibitory effect on other food spoilage microbes and potential pathogens. Strains of Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Streptococcus mutans, Saccharomyces cerevisiae and Zygosaccharomyces rouxii were grown in the presence of fermented and unfermented rooibos tea water extracts. The effect that fermented rooibos tea had on the growth of all the microbes tested was in the following order: Staph. aureus (90.8% decrease in growth) > L. monocytogenes (89.2% decrease in growth) > Strep. mutans (84.1% decrease in growth) > B. cereus (80.3% decrease in growth) > Sacch. cerevisiae (77.7% decrease in growth) > E. coli (69.0% decrease in growth). The rooibos tea clearly had an inhibitory effect on the growth of all the microbes, with the exception of the Z. rouxii strain where the presence of the tea water extracts was found to enhance the growth. The inhibitory effect of rooibos tea on the growth of these microbes was shown by changes in the growth parameters with Nmax and IJmaxshowing decreases, while the ld and tlagincreased as the concentration of the tea soluble solids was increased. As with E. coli, the fermented rooibos tea water extracts showed the stronger inhibitory effect on the growth of the various microbes. The data obtained in this study suggests that rooibos tea is not effective as an anti-microbial agent against all yeast species, but will strongly retard the growth of specific Gram-positive and Gram-negative bacteria. As long as rooibos tea is present, strong anti-microbial activity will be observed at a cup of tea concentration of 2.5 g.r1 soluble solids. These results may be of value to support the health claims associated with rooibos tea and may in the future lead to the use of rooibos tea as a "natural" food preservative.
Antibiotic resistant bacteria prevalent in livestock and wildlife species in South Africa
(Stellenbosch : Stellenbosch University, 2019-04) Van den Honert, Michaela Sannettha; Gouws, Pieter Andries; Hoffman, Louwrens C.; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Much research has focussed on the fate of antibiotics in clinical settings whereas research of antibiotics in natural environments has been comparatively limited. It has been hypothesised that wildlife could play a significant role in the development of antibiotic resistant bacteria in nature as a variety of wildlife species carry antibiotic resistant bacteria and cover a large territory throughout their lifespan The aim of this study was to determine whether wild ungulates, namely, African buffalo (Syncerus caffer), black wildebeest (Connochaetes gnou), blue wildebeest (Connochaetes taurinus), bontebok (Damaliscus pygargus), eland (Taurotragus oryx), fallow deer (Dama dama), impala (Aepyceros melampus) and springbok (Antidorcas marsupialis), host antibiotic resistant bacteria, specifically, Escherichia coli, Enterococcus faecalis and Staphylococcus aureus, from various South African farms. The Kirby-Bauer disk diffusion method was used according to the Clinical and Laboratory Standards Institute 2018 guidelines. Overall, antibiotic resistance among the wild ungulate species was low towards the selected antibiotics. On average, the antibiotic resistance levels were 8% E. coli (N= 353), 4% E. faecalis (N= 194) and 22% S. aureus (N= 106). The highest antibiotic resistance was towards antibiotics which are of natural origin, namely the β-lactams and streptomycin. These antibiotics are found in the soil microbiome, produced by Actinobacteria. In addition, certain resistant genes were detected using the polymerase chain reaction in isolates which showed phenotypic resistance. The resistant genes sul1 (40%), sul2 (80%), sul3 (0%), blaCMY (98%), tetA (63%), tetB (75%), tetC (0%) and aadA (98%) were detected in resistant E. coli isolates (N= 44); tetK (7%), tetL (100%), tetM (100%), blaZ (100%), vanA (95%) and vanB (10%) in resistant S. aureus (N= 5) and E. faecalis (N= 22) isolates. The results of this study indicate that wildlife can be considered a natural reservoir of antibiotic resistant genes. The wildlife were also found to be more multi-drug resistant than the livestock. Thus it is speculated that these resistant genes are picked up from the soil and the surrounding environment and are spread by the animals as well as by other natural vectors like the wind and flies. Various factors and agricultural practices were found to influence the antibiotic resistance of the bacteria harboured by the wildlife species, namely, co-grazing with livestock, the practice of wildlife supplementary feeding and farm history of antibiotic use. Bacteria isolated from game meat was frequently more antibiotic resistant than bacteria from the faeces, indicating human cross-contamination during slaughter. The level of antibiotic resistance determined in this study from the bacteria of the wildlife from pristine areas, could serve as a baseline for monitoring the influence of human activities on the development of antibiotic resistance in various environments, which this study contributed towards.
Antimicrobial effects of chitosan and essential oils on postharvest diseases of pomegranate fruit
(Stellenbosch : Stellenbosch University, 2017-12) Munhuweyi, Karen; Opara, Umezuruike Linus; Caleb, Oluwafemi James; Lennox, Cheryl L.; Sigge, G. O.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: Pomegranate (Punica granatum L.) fruit diseases often caused by a range of fungi and bacteria, pose significant financial, nutritional and postharvest losses along the value chain. This study aimed at identifying pomegranate postharvest diseases in South Africa and improving the shelf life of whole and minimally processed pomegranates using chitosan and essential oils (EOs). To identify pomegranate postharvest pathogens and their origin in the value chain, samples of leaves and fruit at different development stages were collected from commercial orchards of cultivars ‘Herskawitz’ (mid harvest) and ‘Wonderful’ (late harvest) located in the Western Cape region of South Africa. Fungi were isolated from healthy and intact pomegranate flowers (open, closed, diheased), immature fruitlets buds, immature green fruit and ripe pomegranate fruit as well as leaves. Isolated fungal pathogens were identified using phylogenetic analysis of the internal transcribed spacer (ITS: ITS1 and ITS2) of the nuclear ribosomal DNA and the 5.8S ribosomal RNA genes. Aspergillus niger Tiegh., Cytospora spp., Clonostachys spp., Embellisia eureka E.G. Simmons, Pestalotiopsis spp., Nigrospora oryzae and Rhizopus stolonifer Ehrenb., were associated with non-disinfected plant materials. The major pomegranate spoilage pathogens were isolated from surface sterilised samples and comprised of Alternaria spp., Aureobasidium pullulans, Botrytis spp., Penicillium spp., and Pilidiella granati Sacc. (syn. Coniella granati [Sacc.] Petr. & Syd.). The open flower stage had the highest incidence of spoilage pathogens and the same pathogens were isolated from fruit at postharvest. Pathogenicity tests were carried out on the major postharvest spoilage pathogens isolated namely Botrytis sp., Penicillium sp. and P. granati. This is the first report of P. granati on pomegranate fruit in South Africa. A restriction fragment length polymorphism (RFLP) tool was developed for the detection of pomegranate postharvest pathogens. This tool will be important in the monitoring of pomegranate pathogens in orchards and packhouses. The antifungal activity of crab shell chitosan (0-10 g/L) and fludioxonil (0-1.0 g/L) was tested against Botrytis sp., Penicillium sp. and P. granati previously isolated from pomegranate. Pathogen sensitivity to crab shell chitosan based on the EC50 values (concentration causing a 50% reduction in mycelial growth) showed that P. granati (EC50-0.47 g/L) was the most sensitive followed by Botrytis sp. (EC50-1.19 g/L) and Penicillium sp. (EC50 2.21 g/L). For fludioxonil Penicillium sp. (EC50 0.02 mg/L) was the most sensitive followed by P. granati (EC50 0.48 mg/L) and Botrytis sp. (EC50 0.09 mg/L). Pre-treating wounded fruit (preventive treatment) with chitosan prior to pathogen inoculation gave better disease control (30-66% decay reduction) compared to introducing the chitosan after pathogen inoculation as a curative strategy (18-38%). Applying chitosan (0, 2.5, 7.5 and 15 g/L) as an edible coating on minimally processed pomegranate arils prior to cold storage significantly (P<0.05) lowered counts for mesophilic aerobic bacteria, yeast and moulds. In addition, the chitosan treatment also maintained the physico-chemical attributes of the arils (total soluble solids (TSS), titratable acidity (TA), moisture, colour, firmness, total phenolics, anthocyanins and ascorbic acid). The findings demonstrate that crab shell chitosan can be considered as a potential green fungicide for postharvest disease management of both whole and minimally processed pomegranate fruit. A follow up study to enhance the antimicrobial properties of chitosan was conducted using chitosan as a polymeric carrier of volatile EOs (cinnamon, lemongrass and oregano). The EOs were assayed for antifungal activity against Botrytis sp., Penicillium sp., and P. granati. Lemon grass was the least effective EO as it failed to provide complete inhibition of any of the fungal pathogens while oregano EO was the most potent as it gave complete inhibition of P. granati by both vapour and direct contact methods. In vivo application of chitosan-oregano as an edible coating effectively controlled fungal growth by 59-100% but induced negative effects on the fruit skin. When applied as active film, the chitosan-oregano film still significantly (P < 0.05) reduced fruit decay by 34-100% without elucidating cosmetic damage to the fruit rind. The findings revealed the potential application of chitosan-EO based films in developing antimicrobial based active food packaging systems. To further improve use of EOs in antimicrobial packaging, cinnamon and oregano EOs were encapsulated in β-cyclodextrin (β-CD) and a nanofibrous matrix based on chitosan and polyvinyl alcohol (PVA) to reduce the thermal instability of the EOs and achieve prolonged release. A GC-MS analysis revealed that the β-CD was significantly (P < 0.05) more efficient in encapsulation of cinnamon EO (4.86%), compared to oregano EO (1.75%). However, similar EO concentrations were obtained when the essential oils were incorporated into electrospun chitosan based nanofibres. The EO based β-CD microcapsules and nanofibres both had antimicrobial effect on Botrytis sp. and thus could be used in antimicrobial packaging. This study identified the major postharvest spoilage pathogens of pomegranates in the Western Cape Region of South Africa and further determined that the orchard was the major source of these pathogens. Crab shell chitosan independently and in combination with EOs was shown to effectively control pomegranate postharvest pathogens on whole and minimally processed fruit. While exposing the pomegranate fruit to direct contact with EO emulsions reduced postharvest spoilage it also resulted in a negative cosmetic appearance of the fruit rind. However, exposing fruit to in-direct contact with encapsulated EOs controlled postharvest spoilage without affecting the fruit cosmetic appearance.
The antioxidant activity of South African wines in different test systems as affected by cultivar and ageing
(Stellenbosch : University of Stellenbosch, 2002-03) De Beer, Dalene; Joubert, E.; Gelderblom, W. C. A.; Manley, M.; University of Stellenbosch. Faculty of Agriscience. Dept. of Food Science.
ENGLISH ABSTRACT: Phenolic compounds in wine, due to their antioxidant activity, are reportedly responsible for the health-promoting properties of wines. The effect of cultivar and in-bottle ageing on the antioxidant activity of South African wines in different types of antioxidant assays was, therefore, investigated. The antioxidant activity of commercial South African red (Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) and white (Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) cultivar wines was compared using the 2,2’-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation (ABTS·+) scavenging, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) scavenging and microsomal lipid peroxidation (MLP) assays. The red wines was more effective than the white wines on an “as-is” and an equal total phenol content. The total antioxidant activity (TAAABTS and TAADPPH) of Ruby Cabernet was the lowest of the red wines, but the antioxidant potency (APABTS and APDPPH) of red wine phenolic fractions did not differ (P ³ 0.05). Ruby Cabernet and Pinotage were the least effective inhibitors of MLP, while Merlot was the most effective of the red wines. Pinotage phenolic fractions had lower (P < 0.05) APMLP than that of other red wines. Of the white wines, Chardonnay and Chenin blanc had the highest and lowest effectivity respectively according to all antioxidant parameters. Ascorbic acid present in some wines increased and decreased their TAA and % MLP inhibition respectively. TAA and % MLP inhibition correlated well (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavanol content of red wines and tartaric acid ester content of white wines. The % MLP inhibition also correlated well with flavanol content of white wines. No correlation (P > 0.01) was obtained between TAA or % MLP inhibition and monomeric anthocyanin content of red wines. In the deoxyribose assay, red wines were more pro-oxidant and exhibited lower hydroxyl radical scavenging and metal chelating abilities than white wines. The effect of in-bottle ageing on antioxidant activity of wines was determined using the ABTS·+ and DPPH· scavenging assays. The TAA and total phenol content of experimental red (Pinotage and Cabernet Sauvignon)and white (Chardonnay and Chenin blanc) cultivar wines, decreased (P < 0.05) during 12 months of storage at 0, 15 and 30 ºC. The TAAABTS of Cabernet Sauvignon and Chardonnay, stored at 30 ºC were lower (P < 0.05) than at 0 ºC. The APABTS and APDPPH of most wines also decreased during storage. The monomeric anthocyanin content of red wines decreased (P < 0.05) rapidly at 15 and 30 ºC. The flavanol content of wines (except Chenin blanc) increased during the first 9 months, decreasing again after 12 months, while minor changes in the flavonol and tartaric acid ester content of both red and white wines were observed. The TAAABTS exhibited a good correlation (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavonol and tartaric acid ester content of red and white wines and flavanol content of white wines. The monomeric anthocyanin content of red wines correlated (r = 0.50, P < 0.001) weakly with TAAABTS. The decrease in the TAAABTS of wines could thus be mainly attributed to a decrease in their total phenol content.
The antioxidant and antimutagenic activities of Cyclopia spesies and activity-guided fractionation of C. intermedia
(Stellenbosch : Stellenbosch University, 2003-03) Richards, Elizabeth Siân; Joubert, E.; Gelderblom, W. C. A.; Manley, M.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: Please refer to fulltext for abstract
Antioxidant capacity of Pinotage wine as affected by viticultural and enological practices
(Stellenbosch: University of Stellenbosch, 2006-12) De Beer, Dalene; Joubert, E.; Marais, Jeannine; Manley, M.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science.
The aim of the study was to provide the South African wine industry with guidelines for the production of Pinotage wines with optimal total antioxidant capacity (TAC), while retaining sensory quality. The contribution of individual phenolic compounds to the wine TAC is important in this regard. The wine TAC was measured with the 2,2 -azino-di(3-ethylbenzo-thiazoline-sulphonic acid radical cation) (ABTS +) scavenging assay. The contributions of individual phenolic compounds to the wine TAC were calculated from their content in the wines and the Trolox equivalent antioxidant capacity (TEAC) of pure phenolic standards. The effects of climate region, vine structure, enological techniques (pre-fermentation maceration, juice/skin mixing, addition of commercial tannins, extended maceration) and maturation (oak barrels, alternative oak products, oxygenation) on the phenolic composition, TAC and sensory quality of Pinotage wines were also investigated. The TEAC values of quercetin-3-galactoside, isorhamnetin and peonidin-3-glucoside were reported for the first time. TEAC values observed for most compounds were much lower than those reported previously, although TEAC values for gallic acid, caftaric acid, caffeic acid and kaempferol were consistent with some previous reports. Caftaric acid and malvidin-3-glucoside were the largest contributors to the wine TAC. The contents of monomeric phenolic compounds and procyanidin B1, however, only explained a small amount (between 11 and 24%) of the wine TAC, with the remaining TAC attributed to oligomeric and polymeric phenolic compounds and other unknown compounds. Some synergy between different monomeric phenolic compounds was also demonstrated. All the viticultural and enological factors investigated affected the phenolic composition of Pinotage wines, while the wine TAC was only affected by some treatments. Changes in wine TAC could not always be explained by changes in phenolic composition as the contribution of oligomeric, polymeric and unknown compounds could not be assessed, but could play a large role. Differences in wine colour were also difficult to explain due to the large number of factors involved and the dark wine colour, which made objective measurements difficult. The concentration of vitisin A, an orange-red pyranoanthocyanin, was increased consistently as a result of prefermentation maceration treatments and affected the wine colour of oxygenated wines. Increased wine TAC was observed when cultivating Pinotage grapes on bush vines and in cooler climatic regions, compared to cultivation on trellised vines in warmer climatic regions. All the climatic regions and vine structure treatments, however, resulted in wines with good sensory quality. In terms of enological techniques, pumping-over, as opposed to punching-down and rotor treatments, is not recommended as a juice/skin mixing technique, due to reduced wine TAC, colour and sensory quality. Pre-fermentation maceration, addition of commercial tannin preparations, and oak maturation using traditional and alternative treatments, resulted in improved sensory quality, but with no change in wine TAC. However, optimisation of the tannin addition protocol may result in increased wine TAC if additions are made after fermentation or higher dosages are used. Oxygenation of Pinotage wine needs further investigation to optimise the protocol, as improvements to the wine colour and fullness were observed for some treatments, but loss of sensory quality and TAC were observed in most cases.
Antioxidant properties and effect of forced convection roasting on South African wheats
(Stellenbosch : Stellenbosch University, 2016-03) Zhang, Songlei; Manley, Marena; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: See full text for abstract.
Die antosianienpigmente van Vitis vinifera cv. Barlinka
(Stellenbosch : Stellenbosch University, 1964-12) Basson, D. S. (David Stephanus); Koeppen, B. H.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science .
ENGLISH ABSTRACT: no abstract available
Application of biogranules in the anaerobic treatment of distillery effluents
(Stellenbosch : Stellenbosch University, 2000-12) O'Kennedy, Onicha Deborah; Britz, T. J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: The distillery industry produces large volumes of waste water with a high organic content throughout the year. These effluents must be treated in some manner before being discharged or recycled in the factory. Several treatment options are in use presently, but they all have disadvantages of some nature, such as long retention times, bad odours or the need for large areas of land. Considerable interest has been shown in the application of anaerobic digestion, especially the UASB design (upflow anaerobic sludge blanket), to treat this high strength waste water. Thus, the aim of this study was to investigate the efficiency of an upflow anaerobic sludge blanket (UASB) bioreactor using full-strength distillery effluent. The activity of the bacteria in the biogranules was also evaluated by developing an easy and reliable activity method to estimate the general biogas and methanogenic activity and to calibrate this method using different anaerobic granules from different sources. The influence of high strength distillery effluent on the anaerobic digestion process was investigated using a mesophilic lab-scale UASB bioreactor. During the experimental study, the organic loading rate (OLR) was gradually increased from 2.01 to 30.00 kgCOD.m-3.d-1, and simultaneously, the substrate pH was gradually lowered from 7.0 to 4.7. It was found that at an OLR of 30.00 kgCOD. m-3.d-1,the pH, alkalinity and biogas production stabilised to average values of 7.8, 6 000 mg.l-1 and 18.5 I.d-1 respectively. An average COD removal> 90% was found indicating excellent bioreactor stability. The low substrate pH holds considerable implications in terms of operational costs, as neutralisation of the biorector substrate is no longer necessary. The accumulation of fine solids present in the distillery substrate was found at the higher OLR's and resulted in the granular bed increasing with subsequent biomass washout and a lowering in efficiency parameters. However, a possible pre-treatment filtration of these fine solids would eliminate this problem. The success of the upflow anaerobic sludge bed (UASB) process is mainly due to the capability of retaining the active biomass in the reactor. Over the years, several methods have been developed to characterise and quantify sludge activity but each has advantages and disadvantages. There is thus an increasing need for a rapid method to evaluate the activity of the granular biomass. The activity method of Owen et al. (1979) as adapted by Lamb (1995), was thus evaluated in terms of efficiency and applicability in determining the activity of granular samples. The method was found to be inaccurate as well as time consuming and it was thus modified. Results obtained with the modified assay method were found to be more accurate and the impact of the different test substrates (glucose, lactate, acetate and formate) on activity, was more evident. The activity of seven different anaerobic granules, was subsequently evaluated. Biogas (Ss) and methanogenic (SM) activity was not measured in volume of gas produced per unit COD converted or volatile suspended solids (VSS), but as tempo of gas production (ml.h-1) in a standardised basic growth medium. The activity data obtained were also displayed as bar charts and "calibration scales". This illustrative depiction of activity data gave valuable information about population dynamics as well as possible substrate inhibition. The "calibration scales" can also be used to group the general biogas (Ss) and methanogenic activities (SM) of any new biogranule relative to active (O-type) and inactive (W-type) anaerobic granules, providing that the same method of activity testing is used. The "calibration scales" can thus be used to give a fast indication of how the activity value of one sample relates to the activity values of other granules, even when using different test substrates.
The application of Fourier transform near infrared (FT-NIR) spectroscopy in the wine, fruit and dried fruit industries of South Africa
(Stellenbosch : Stellenbosch University, 2000-12) Van Zyl, Anina; Manley, M.; Joubert, E.; Wolf, E. E. H.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science .
ENGLISH ABSTRACT: This study shows Fourier transform near infrared (FT-NIR) spectroscopy's application on wine, fruit and dried fruit for quantitative determinations or as a discriminative method for classification purposes. During wine production optimum yeast growth, resulting in healthy alcohol fermentation rates, is monitored by the amount of free amino nitrogen (FAN) present in the must. The status of malolactic fermentation (MLF) in Chardonnay wines is monitored by determining the degree of conversion of malic to lactic acid. Ethyl carbamate (EC), a suspected carcinogen, is mainly formed during ageing of wine and is restricted by legislation in some countries. It is therefore necessary to determine the EC content in wine. Fourier transform near infrared spectroscopy can be used on wine as a rapid method to measure the °Brix (residual sugars) content of must and to discriminate between different must samples in terms of their FAN values. It can also be used as a rapid method to discriminate between Chardonnay wine samples in terms of the MLF status and between table wine samples in terms of the EC content. Calibrations were derived and it was found that a very strong correlation existed in the sample set for the FT-NIR spectroscopic predictions for °Brix (r = 0.99, SEP = 0.31%), but poorer correlations for the FAN (r = 0.405, SEP = 275%), malic acid (r = 0.64, SEP = 1.02%), lactic acid (r = 0.61, SEP = 1.35%) and EC predictions (r = 0.47, SEP = 3.6%). When soft independent modelling by class analogy (SIMCA) was applied as a discriminative method, the must and wine samples were classified in terms of their FAN and EC values and MLF status, respectively, obtaining results with recognition rates exceeding 80%. The canning of peaches has become a significant industry in South Africa, producing approximately 4.1 million cartons per year. Fourier transform near infrared spectroscopy was applied as an alternative non-destructive method for the quantitative determination of the total soluble solid (TSS) content of whole fresh peaches. The TSS content of fresh clingstone peaches is an indication of the internal quality, maturity and perceived sweetness of the fruit for the peach canning industry. By determining the TSS, fresh peaches can be graded and the farmers compensated accordingly. Results obtained by building QUANT+™calibrations for the TSS content (r = 0.96, SEP = 0.55%) showed acceptable accuracy and can replace the present destructive methods. Peak periods during the harvesting season necessitate storage of peaches for up to three weeks before canning. Approximately 5 - 10% of the peaches stored, disintegrate during canning due to loose skin, large stone cavities, soft flesh and rot. The storage potential of fresh clingstone peaches can be successfully predicted with FT-NIR and SIMCA models, using subjective internal quality evaluations. Results with recognition rates exceeding 80% were obtained in most cases and this method proved useful as a non-destructive method of quality assessment. By applying this method, losses caused when storing peaches with poor storage quality will be reduced. The golden sultana industry plays an important role in the dried fruit exporting market of South Africa. Due to the large numbers of consignments that must be checked upon arrival, and the need for rapid decision making during processing, it is essential to replace the present time-consuming analytical methods. Fourier transform near infrared spectroscopy was used as a rapid, analytical technique to determine whether the S0₂ and moisture contents of sultanas are within specifications upon arrival at the factory and during processing. High positive correlation was found between the measured values and those predicted by FT-NIR spectroscopy for S0₂ (r = 0.99, SEP = 24.09%) and moisture (r = 0.99, SEP = 0.051 %) contents.
Application of imaging techniques to evaluate micro-structural and compositional modification during Barley malting
(Stellenbosch : Stellenbosch University, 2019-12) Collins, Carla; Marena, Manley; Saeys, Wouter; Nguyen-Do-Trong, Nghia; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Over time, barley (Hordeum vulgare) has been domesticated from its wild relative, Hordeum spontaneum to cultivate breeds specialised for malting. The malting industry relies on good quality grain, with good malting characteristics from specialized breeding programmes. These malting characteristics may be expressed in a myriad of ways – most notably in malting barley cultivars, the evidence lies within the starchy endosperm. The endosperm consists of a protein matrix embedded with starch granules. Often, the structure of the endosperm may be described as either mealy or steely based on the arrangement of starch granules and proportions within the matrix. The endosperm of a mealy barley grain has a loosely packed structure with several air spaces between starch granules, while also having a larger portion of A-type starch granules compared to B-type starch granules. An endosperm that is described as steely has a structure that is tightly packed with small, B-type starch granules filling many of the voids to result in a dense endosperm. Due to the arrangement of the endosperm, water uptake into a barley grain may be influenced during the malting process. It has been theorised that mealy barley grain with a less dense endosperm structure allows water uptake to occur with ease, compared to steely barley grain where hydration may be hindered. Obstructed water uptake and uneven distribution of water throughout the barley grain in turn limits the activation of hydrolytic enzymes and subsequent malt modification. With the aid of scanning electron microscopy (SEM), the endosperm structure of barley grain may be closely inspected to evaluate the properties of a good and a poor malting cultivar. Three conventional fixation methods were compared to establish a technique to observe the endosperm structures with minimal artefacts. It was found that plunge freezing and cracking open of grain was an effective method in preserving the structure of the endosperm, compared to chemical fixation that delivered artefacts and cryo-sectioning that caused damage to structures. To observe the endosperm matrix throughout the malting process, plunge freezing was done during successive days of germination and evidence of starch degradation by enzymatic activity was seen in situ. Using the method of plunge freezing, 11 local malting barley cultivars with varying brewing performances were compared to identify characteristics that may predict its brewing performance. Evidence was found that the endosperm of a good converter appears to have a more loosely packed structure with accompanying air spaces, while the endosperm of a poor converter has characteristics of a steely endosperm that slows water uptake. The fact that water has good absorbance properties in the near infrared (NIR) region, lends to the advantage of NIR applications for the study of food products that have a moderate to high water content. Applications of NIR have evolved to incorporate hyperspectral imaging (HSI) that allows specialised applications in the field of cereal grain quality control. As barley grain hydrate during the malting process, modes of water uptake may differ between a good and a poor converter. This theory was investigated using NIR-HSI (in the wavelength range between 850 and 2500 nm) for barley breeders to identify good malting cultivars for the brewing industry. In order to track hydration of barley grain, multivariate image analysis was employed and score plots were recoloured successively in order to track changes that occur over the course of barley grain hydration. Using partial least squares discriminant analysis (PLS-DA), good converting malts were distinguished from poor converting malts at key timepoints along the steeping process. The mean spectra of individual grains were assigned to a most probable class above 0.50 probability. Classification error before steeping was high (27.1%) and gradually lowered to give the most accurate classification model (classification error of 10.4%) at 37 hours of steeping.
Application of postharvest chemical treatments to enhance storage and shelf life of pomegranate fruit (cv. Wonderful)
(Stellenbosch : Stellenbosch University, 2017-03) Atukuri, Julian; Opara, Umezuruike Linus; Olaniyi, Amos Fawole; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: Pomegranate fruit is susceptible to a number of postharvest quality problems such as external and internal decay, weight loss, internal browning, chilling injury and husk scald. Postharvest treatments offer the possibility of alleviating these challenges and maintain fruit quality. The aim of the study was to investigate the potential of exogenous application of chemical treatments (putrescine (PUT) and fludioxonil (FLU)) in reducing the incidence of postharvest physiological disorders of pomegranate fruit (cv. Wonderful). Fruit were treated at three concentrations (putrescine – 1, 2 and 3 mM; fludioxonil – 150, 300 and 600 mg/L) and stored for 4 months at 5 °C plus an additional 4 days at 20 °C (shelf life). The effects of the chemical treatments and storage duration on fruit physiological response and quality were investigated. The results showed that treating pomegranate fruit with putrescine at different concentrations (1, 2 and 3 mM) reduced incidence of physiological disorders such as external fruit decay, chilling injury and husk scald during the first 3 months of storage. However, putrescine had no effect on internal disorders such as internal decay and aril browning. Physico-chemical attributes such as peel colour, aril colour, TSS, TA and pH were not significantly (p > 0.05) affected by putrescine application. After four months of storage, treated samples had firmer fruit and arils while the control had softer fruit with lower firmness (10.12 ± 0.40 N) and aril hardness (143.20 ± 3.84 N). Fruit treated with 2 mM PUT had the best sensory quality (crispness, sweet taste, juiciness) after 3 months of storage. Although 3 mM PUT effectively reduced physiological disorders, 2 mM PUT had the advantage of both reducing the external disorders and maintaining fruit sensory quality during storage up to 3 months. Fludioxonil was very effective in reducing decay incidence among treated fruit, with 600 mg/L as the most effective FLU concentration having 15.7 % lower decay than control. However, other physiological disorders such as aril browning, chilling injury and husk scald were more pronounced in treated fruit. Fruit firmness was maintained among treated fruit while aril texture was not significantly (p > 0.05) affected. Control fruit had higher aril redness (a*) and intensity (C*) compared to fruit treated with FLU. The chemical attributes TA, TSS and BrimA generally decreased with storage for all FLU concentrations. Fruit treated with 600 mg/L were related to eating attributes for crisp, juicy and sweet fruits. Fruit were successfully stored up to 3 months without adversely affecting quality and 600 mg/L was the most effective FLU concentration. A further study on the effects of the PUT and FLU treatments on phytochemical and volatile composition of fruit revealed that fruit juice ascorbic acid content decreased slightly while total phenolic content (TPC) significantly decreased during storage for both chemicals. Fruit treated with FLU had higher TPC for the first 3 months while fruit treated with PUT only showed high TPC after month 2 of storage. Total anthocyanin content (TAC) of fruit initially increased to values above harvest regardless of FLU concentration. However, TAC decreased as storage progressed with no significant difference (p > 0.05) between FLU concentration at the end of the storage duration. On the other hand, TAC of PUT treated fruit significantly reduced throughout storage (except at month 2), with no significant differences observed among PUT concentrations at the end of storage. In contrast, the antioxidant capacity of both FLU and PUT treated fruit increased throughout the storage duration. Furthermore, a total of 31 and 32 volatile compounds were identified in fruit treated with FLU and PUT, respectively. Six chemical groups (alcohols, aldehydes, acids, ketones, esters and terpenes) were identified among fruit treated with FLU, while five (alcohols, aldehydes, acids, esters and terpenes) were detected in fruit treated with PUT. Volatile compounds evolved with prolonged storage, with new compounds, especially terpenes, detected at later storage durations. Accumulation of terpenes had adverse effects on fruit sensory quality and therefore storage for long duration may result in lower fruit flavour. Overall, the study provided insightful information on the potential of putrescine and fludioxonil treatments in reducing pomegranate fruit postharvest disorders and their effects on fruit edible and nutritional quality attributes. The application of FLU greatly reduced fruit decay but not chilling injury, husk scald and aril browning while PUT alleviated all these physiological disorders. However, PUT and FLU did not effectively reduce weight loss, and therefore, future studies may focus on combining chemical treatments together with physical treatments such as film wrapping and waxing so as to benefit from the hurdle effect. In addition, combination of FLU and PUT may be explored to harness the full potential of the two chemical treatments.
Application of science and technology by the South African food and beverage industry
(Academy of Science of South Africa, 2018) Ronquest-Ross, Lisa-Claire; Vink, Nick; Sigge, G. O.
Significant shifts in the type of foods consumed by South Africans have taken place since 1994 and packaged food and beverage innovation has accelerated since then. Globally, advances in science and technology have benefitted food processing and food manufacturing technologies and systems. Significant capital investments have been made by the South African food and beverage manufacturing industry (SAFBMI). It is, however, not clear which technology areas have received investments and for what purposes. The objective of this study was thus to understand how the SAFBMI has invested in and applied science and technology since 1994. Data were sourced from food and beverage trade magazines, dating from 1986 to 2012. Trends over the past 30 years were analysed to determine the application of science and technology. The findings suggest that the dairy, soft drinks and bakery sectors have been most active. The main advances were to upgrade manufacturing facilities and build new plants to increase capacity, deliver new products and improve efficiencies and product quality and safety. Investments to improve thermal processing and packaging were also noted. We found evidence of the application of commercially available new preservation technologies and a low level of experimentation with non-commercial novel technologies by the SAFBMI. South Africa appears to be keeping pace with advances in food manufacturing in automation, process control and quality and food safety practices, material handling, and centralised distribution centres with warehouse management systems. Continued investment in food science and technology research will ensure that the growing consumer demand for packaged foods and beverages is met.
Aspalathin-enriched green rooibos extract reduces hepatic insulin resistance by modulating PI3K/AKT and AMPK pathways
(MDPI, 2019-02-01) Mazibuko-Mbeje, Sithandiwe E.; Dludla, Phiwayinkosi V.; Roux, Candice; Johnson, Rabia; Ghoor, Samira; Joubert, Elizabeth; Louw, Johan
We previously demonstrated that an aspalathin-enriched green rooibos extract (GRE) reversed palmitate-induced insulin resistance in C2C12 skeletal muscle and 3T3-L1 fat cells by modulating key effectors of insulin signalling such as phosphatidylinositol-4,5-bisphosphate 3-kinase/protein kinase B (PI3K/AKT) and AMP-activated protein kinase (AMPK). However, the effect of GRE on hepatic insulin resistance is unknown. The effects of GRE on lipid-induced hepatic insulin resistance using palmitate-exposed C3A liver cells and obese insulin resistant (OBIR) rats were explored. GRE attenuated the palmitate-induced impairment of glucose and lipid metabolism in treated C3A cells and improved insulin sensitivity in OBIR rats. Mechanistically, GRE treatment significantly increased PI3K/AKT and AMPK phosphorylation while concurrently enhancing glucose transporter 2 expression. These findings were further supported by marked stimulation of genes involved in glucose metabolism, such as insulin receptor (Insr) and insulin receptor substrate 1 and 2 (Irs1 and Irs2), as well as those involved in lipid metabolism, including Forkhead box protein O1 (FOXO1) and carnitine palmitoyl transferase 1 (CPT1) following GRE treatment. GRE showed a strong potential to ameliorate hepatic insulin resistance by improving insulin sensitivity through the regulation of PI3K/AKT, FOXO1 and AMPK-mediated pathways.
Aspalathin-rich green rooibos extract lowers LDL-cholesterol and oxidative status in high-fat diet-induced diabetic vervet monkeys
(2019-05-02) Orlando, Patrick; Chellan, Nireshni; Louw, Johan; Tiano, Luca; Cirilli, Ilenia; Dludla, Phiwayinkosi; Joubert, Elizabeth; Muller, Christo J. F.
Type 2 diabetic patients possess a two to four-fold-increased risk for cardiovascular diseases (CVD). Hyperglycemia, oxidative stress associated with endothelial dysfunction and dyslipidemia are regarded as pro-atherogenic mechanisms of CVD. In this study, high-fat diet-induced diabetic and non-diabetic vervet monkeys were treated with 90 mg/kg of aspalathin-rich green rooibos extract (Afriplex GRT) for 28 days, followed by a 1-month wash-out period. Supplementation showed improvements in both the intravenous glucose tolerance test (IVGTT) glycemic area under curve (AUC) and total cholesterol (due to a decrease of the low-density lipoprotein [LDL]) values in diabetics, while non-diabetic monkeys benefited from an increase in high-density lipoprotein (HDL) levels. No variation of plasma coenzyme Q10 (CoQ10) were found, suggesting that the LDL-lowering effect of Afriplex GRT could be related to its ability to modulate the mevalonate pathway differently from statins. Concerning the plasma oxidative status, a decrease in percentage of oxidized CoQ10 and circulating oxidized LDL (ox-LDL) levels after supplementation was observed in diabetics. Finally, the direct correlation between the amount of oxidized LDL and total LDL concentration, and the inverse correlation between ox-LDL and plasma CoQ10 levels, detected in the diabetic monkeys highlighted the potential cardiovascular protective role of green rooibos extract. Taken together, these findings suggest that Afriplex GRT could counteract hyperglycemia, oxidative stress and dyslipidemia, thereby lowering fundamental cardiovascular risk factors associated with diabetes.

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