Masters Degrees (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.
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.
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 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.
Assessment of access to food by households in Epworth (Ward 3) Harare, Zimbabwe
(Stellenbosch : Stellenbosch University, 2024-03) Phiri, Alice; Boatemaa Kushitor, Sandra; Sigge, Gunnar; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Urban food insecurity is on the rise globally, particularly in the global south which is experiencing a surge in urbanization. High poverty levels, high levels of unemployment, volatile exchange rates, inflation, rising food prices, and generally high cost of living are some of the drivers of urban food insecurity in sub-Saharan Africa. Zimbabwe has gone through decades of macro-economic and political instability increasing the vulnerability of urban and peri-urban dwellers to food insecurity. This study assessed how households in Epworth, Ward 3 access food and the degree of coping when households do not have enough food or income to purchase food. The study sought to determine the level of food insecurity in Epworth Ward 3, the levels of income of households in Epworth, their sources of income and food, the percentage of income they spend on food and the degree of coping employed by households. To answer these questions quantitative research based on a case study approach was carried out in Epworth Ward 3 in which 200 households were sampled using a random sampling technique. A questionnaire that adopted the FANTA questions (Coates et al., 2007) was used to capture the Household Food Access Insecurity Score (HFIAS), Household Dietary Diversity Score (HDDS), Food Consumption Score (FCS), and the Reduced Coping Strategy Index (rCSI) indicators of food security. Findings from the research showed that more than half of the sampled households were moderately and severely food insecure. A greater number of households in Epworth Ward 3 consumed 2 meals per day. There is varied dietary diversity among the sampled households however, there is a sizeable population that consumes poor diets. Most households in Epworth rely on market purchases as their source of food. Total monthly incomes of the sampled households are very low and households spent a greater proportion of their incomes on food. Results showed that households with low monthly incomes were more food insecure. The study also showed that the more food insecure the higher the degree of coping. Overall food insecurity in Epworth Ward 3 is still very high. The research recommended continuous monitoring of the food security situation in Epworth with evolving macroeconomic conditions in Zimbabwe to continuously have a clear picture of the food insecurity in the area. This will inform the local board and decision-makers to tailor-make interventions that address the needs of different households in Epworth. Since most households rely on street and mobile vendors as sources of food there is a need to monitor and assess the safety and hygiene practices. The research recommends school feeding programs to increase the number of meals consumed by school-going children thereby improving their food and nutrition security situation. The researcher also recommends the government to introduce social safety net programs in Epworth as households are in precarious food security situation.
Assessment of hectolitre mass (HLM) equipment and HLM measurements of oats
(Stellenbosch : Stellenbosch University, 2012-03) Emvula, Sakeus; Manley, Marena; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: Hectolitre mass (HLM) measurements allow rapid and accurate determination of grain density. HLM devices from different countries (Australia, Canada, France, Germany, South Africa, the United Kingdom and the United States of America [USA]) have been investigated for their effect on the HLM measurements of oats. In addition, the potential of near infrared (NIR) hyperspectral imaging has been evaluated to distinguish between oat samples with different HLM values. Comparing HLM measurements obtained from the respective devices, the USA and the South African devices resulted in significantly (P<0.05) lower HLM values compared to the other devices where as the German device resulted in higher values (P<0.05) than the other devices. HLM values from all the devices were highly correlated with intra-class correlation (ICC) consistency values of at least 0.90. These high correlations would allow direct replacement of the South African device with any of the other devices. The equipment selected as replacement should ideally be calibrated according to the ISO 7971-3 standard (i.e. the device currently used in Germany). HLM values significantly (P<0.05) increased when oat samples were rubbed before measurements were made, indicating the importance of continuation of this sample preparation step. The investigation on the effect of the operator on HLM determinations showed that the unskilled operator measured HLM values significantly different to those obtained by the skilled operator. This emphasises the importance of training in spite of HLM measurements being a simple procedure. A poor correlation (r = 0.18) was found between protein content and HLM values of oat samples. Moisture content significantly affected the HLM values of oats and results clearly showed a decrease in HLM values with increasing moisture content. Scanning electron microscope (SEM) micrographs revealed that the starch granules became swollen and that they increased in size with an increase in moisture content, resulting in a decrease in HLM. NIR hyperspectral imaging offers the testing of individual grains non-destructively. This is often required by plant breeders because they subsequently need to plant selected grains. NIR offers this option to plant breeders. NIR hyperspectral imaging, which combines NIR spectroscopy with digital imaging, was used to distinguish between six oat samples with varying HLM values. NIR spectroscopic differences were observed between the images of the two samples with the highest and lowest HLM values (60.2 and 49.35 kg.hL-1). Less distinct differences were observed in the NIR hyperspectral images of two samples differing by less than 2.0 kg.hL-1. Although mixed oat samples were used, these preliminary results established the possible use of NIR hyperspectral imaging in evaluating oat samples from breeding trials. The use of this technique could also be extended to evaluation of other quality characteristics of oats.
Assessment of microbial levels in the Plankenburg and Eerste Rivers and subsequent carry-over to fresh produce using source tracking as indicator
(Stellenbosch : Stellenbosch University, 2012-03) Huisamen, Nicola; Sigge, G. O.; Britz, T. J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: The agricultural sector of South Africa is currently facing a serious water crisis. The decreased availability of water as a result of climate change and the constantly growing population has left many farmers increasingly dependant on surface water as primary source of irrigation. Urbanisation along with out-dated and insufficient wastewater treatment works have all contributed to polluting large volumes of these resources. Consequently, many farmers have been forced to use irrigation water, not only of poor quality, but often water which has been polluted with untreated sewage. As a result, this project aimed at investigating the link between the quality of irrigation water and the impact on the safety of fresh produce. A base-line of the microbial load at three sites along the Plankenburg and Eerste Rivers was established using standard microbial methods for the detection of indicator organisms such as total and faecal coliforms, Escherichia coli and Enterococci as well as potential pathogens that included Salmonella, Listeria, Staphylococcus, endosporeformers and aerobic colony counts. Chemical parameters such as pH, alkalinity, conductivity and chemical oxygen demand (COD) were also monitored, but were not correlated to microbial pollution levels in the rivers. High faecal coliform and E. coli concentrations, ranging from 310 to 7 x 106 cfu.100 mL-1 and 230 to 7 x 106 cfu.100 mL-1, respectively, were detected. The recommended irrigation water guidelines of ≤1 000 (WHO, 1989) and ≤4 000 cfu.100 mL-1 (DWAF, 2008) for faecal coliforms and E. coli were exceeded, indicating faecal pollution and thus a high health risk. This health risk was confirmed when potential pathogens such as Aerococcus viridans, Klebsiella, Listeria monocytogenes and Salmonella typhimurium were detected at all three sites. The carryover of organisms from rivers to produce (green beans and grapes) was investigated by comparing the microbial population of the Plankenburg and Eerste Rivers to the population recovered from irrigation water and the surface of fresh produce. Faecal coliforms, E. coli, Aerococcus viridans, Enterobacter aerogenes, Klebsiella, L. innocua, L. grayi, L. monocytogenes and Staphylococcus aureus were detected in all three sample types, indicating a similarity between the microbial populations found in the river, the irrigation water and produce. Thus, the transfer of potential pathogens from the rivers to produce is a strong possibility. The build-up of organisms on the surface of green beans as a result of multiple irrigations was also confirmed by an increase in faecal coliform concentrations from initial concentrations of none detected to 44 000 cfu.100 mL-1 over a 10 day irrigation period. Finally, microbial source-tracking techniques including multi-antibiotic resistance (MAR) profiling, and the API 20E classification system were used to determine genotypic and phenotypic characteristics of 92 faecal isolates (from irrigation water and produce) and 13 reference strains. Numerical classification systems was used to classify the 105 faecal isolates according to the degree of similarity between the genotypic and phenotypic characteristics of the 105 isolates. A high degree of similarity indicates a high probability that isolates originate from the same strain and therefore from the same source, thereby confirming the transfer of organisms Faecal isolates (93 and 98%, respectively) were found to be resistant to Vancomycin at both the 5 and 30 μg concentrations. The majority of isolates presented some resistance to Erythromycin (15 μg) and Ampicillin (25 μg), with 82% of isolates presenting an inhibition zone ≤4 mm. Isolates were sensitive towards Ciprofloxacin (1 and 5 μg), Ofloxacin (15 μg), Ceftriaxone (30 μg) and Cefotaxime (5 μg), which were able to inhibit the growth of 79.8, 93.3, 79.8, 88.5 and 71.2% of the isolates, respectively. The 13 medical reference strains all presented different genotypic and phenotypic characteristics and thereby indicated a high degree of variability between isolates from the same species. Finally, 35% of the isolates could be grouped together based on similar genotypic and phenotypic characteristics, therefore, more than a third of the faecal isolates obtained from the surface of the fresh produce was as a result of faecal contaminants in the irrigation water. It could therefore be concluded that a health risk is associated with the water from the Plankenburg and to a lesser extent, Eerste River when used as source of irrigation, thereby risking the transfer of potentially harmful organisms, present in the rivers as result of faecal pollution, to the surface of fresh produce.
Assessment of microbial loads of the Plankenburg and Berg Rivers and the survival of escherichia coli on raw vegetables under laboratory conditions
(Stellenbosch : University of Stellenbosch, 2010-12) Barr, Alison; Ackermann, Alison; Britz, T. J.; Sigge, G. O.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Over the last decade, studies on the quality of the water in many of South Africa.s rivers revealed an increase in pollution levels (DWAF, 1996; DWAF, 2000). In agricultural areas of the Western Cape many farmers draw water for irrigation from nearby rivers without knowing what the microbial pollution level is. In order to investigate the current quality of river water in some of the Western Cape.s major rivers and to explore the possibility of pathogen carryover from water onto produce, this research project was initiated. In an exploratory study over a five month period, the microbiological and water chemistry of three selected sites from the upper Berg and two from the Plankenbrug Rivers were assessed. Studied organisms included Salmonella, Staphylococcus, Listeria, endosporeformers, coliforms, Escherichia coli and intestinal Enterococci, while the chemical analysis consisted of pH, alkalinity, conductivity and chemical oxygen demand (COD). Faecal coliform counts ranging from 540 to 1 700 000 cfu.100ml-1 and 490 to 160 000 cfu.100ml-1 were found for the Berg and Plankenbrug Rivers, respectively. The water temperature ranged from 12º to 21ºC with COD values always below 100 mg.L-1. Potential human pathogens such as Salmonella, Staphylococcus, Listeria, endosporeformers, E. coli and intestinal Enterococci were frequently isolated from all five sites that were sampled. These results are of great concern to farmers, fresh produce retailers and consumers alike as the river water is regularly drawn for irrigation of produce that is later consumed raw or after a minimal processing step. From the exploratory study it was concluded that the water from all the sites were not suitable for use in irrigation practices as they regularly exceeded the guidelines for faecal coliforms and E.coli as set out by South African authorities. Irrigation with faecally polluted river water is one way that fruit and vegetables can become contaminated with foodborne pathogens. The risk of disease transmission from potential pathogens present in the irrigation water is influenced by the microbial load present and the numbers carried over to the produce. In this study the carry-over and survival of Escherichia coli on green beans, sugar-snap peas and cocktail tomatoes was assessed under controlled laboratory conditions. The produce was exposed to E.coli under different combinations of exposure times (5, 15 or 30 min), drying times (30 or 120 min) and different inoculum concentration ranges (107, 105, 104, 10³ and 10ª). In all cases a reduction of at least one log value in original inoculum number was found with the 10ª inoculums showing no survivors. Follow-up studies with an exposure time of 60 min and increased drying times of 6 or 12 h. Neither of these parameter changes affected the variation in numbers for the same inoculum or the E.coli survivors. Similar E.coli loads to those detected on the green beans were detected on the sugar-snap peas. The number of survivors on the cocktail tomatoes was much lower than found for the beans and peas. The number of survivors on the cocktail tomatoes was much lower than found for the beans and peas. This was attributed the 'smooth'surface of the tomato skin probably making attachment of the E.coli bacteria difficult. With the exception of the 10ª inoculum range, all E.coli survivors detected on the three types of produce studied exceeded the guideline numbers set for fresh produce. If similar survival patterns are to be found in the environment then results from this study should serve as a warning that the Plankenburg river water is unsafe for use in the irrigation of fresh produce. Some farmers are already treating river water with chlorine prior to irrigation to eliminate the chance of pathogen transfer onto produce. However, this is not a feasible solution for most farmers due to the high cost of implementing a system such as this.
Assessment of microbial loads present in two Western Cape rivers used for irrigation of vegetables
(Stellenbosch : University of Stellenbosch, 2010-03) Lotter, Marijke; Sigge, G. O.; Britz, T. J.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: Agriculture in the Western Cape is not only one of the most important economic sectors but also provides many job opportunities. Over the last few years the sustainability of this successful industry has become threatened by the faecal pollution of rivers used to irrigate produce that will be consumed raw or after minimal processing. This situation not only poses an enormous risk to the health of the consumer but also to farmers who stand to lose their export licenses. The purpose of this study was to determine the microbial types and loads in river water, irrigation water and on irrigated produce. A baseline study was done on four sites in two Western Cape rivers. These sites were chosen to allow for the sampling of river water, irrigation water and irrigated produce so as to determine whether a link between the use of contaminated irrigation water and the microbial population found on irrigated produce exists. The physico-chemical analyses used in the study consisted of: pH, alkalinity, water temperature, conductivity and chemical oxygen demand. The microbial monitoring included the aerobic colony counts (ACC) and the enumeration of the total coliforms, faecal coliforms, staphylococci, enterococci, and aerobic and anaerobic sporeformers present in the water samples. The presence or absence of the potential pathogens like E. coli, Listeria and Salmonella, was also determined. During the baseline study faecal coliform counts as high as 160 000 organisms.100 mL-1 were noted in the Plankenburg River, while counts as high as 460 000 organisms.100 mL-1 were found in the Mosselbank River. Apart from this, high numbers of staphylococci and intestinal enterococci were often found, while E. coli, Listeria and Salmonella were present in samples from both of these rivers. Based on the results of the baseline study on the two rivers it was decided to do a more intensive study on the microbial load of the river and irrigation water as well as irrigated produce from the Mosselbank site. Lettuce and cabbages from a commercial farmer’s fields were chosen as the irrigated produce. During the warmer summer months, ACC counts in the river samples peaked at 12 8000 000 cfu.mL-1, while faecal coliform counts of 1 600 000 organisms.100 mL-1 were found. The three potential pathogens (E. coli, Listeria and Salmonella) were present in all the river samples taken during this period. While the counts of indicator bacteria in the irrigation water was often lower, faecal coliform counts as high as 1 600 000 organisms.100 mL-1 and several other potential pathogens were found on the irrigated lettuce and cabbage. This could indicate a possible “build-up” of contamination on the produce with the repeated application of the tainted irrigation water. According to guidelines published by DWAF in 2008, water to be used for irrigation should not contain more than 4 000 organisms.100 mL-1 faecal coliforms if it is used for the irrigation of crops that are to be consumed raw or after a minimal processing step, as this would increase the health risk to the consumer. Guidelines published by the South African Department of Health are even stricter and state that raw vegetables and fruit should not contain more than 200 coliform organisms per gram, while E. coli and L. monocytogenes should be absent in one gram, and Salmonella spp. in 25 grams of the produce, respectively. From the data obtained during this study it was evident that the two rivers monitored regularly contained faecal indicators at levels much higher than those proposed in national and international guidelines for safe irrigation, making them unfit for the irrigation of MPF’s. It could be concluded that the rivers investigated during this study contained high levels of faecal contamination. Since some of the pathogens isolated from the river and irrigation water and the irrigated produce, it suggests a carry-over of microbial contamination from the river water to the irrigated produce. This was, however, only done using the traditional international methods and the presence of specific pathogens should in future be confirmed by means of molecular techniques.
The assessment of the physico-chemical, microbiological and kinetic parameters of acidulants used in the production of acidified dried sausages made from the meat of blesbok (Damaliscus pygargus phillipsi)
(Stellenbosch : Stellenbosch University, 2015-12) Van den Honert, Mathew Paul; Hoffman, Louwrens C.; Gouws, Pieter Andries; Sigge, G. O.; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
ENGLISH ABSTRACT: The physico-chemical, microbiological and kinetic parameters of Blesbok (Damaliscus pygargus phillipsi) dry acidified sausage produced by chemical acidification were assessed. Initially, Blesbok meat dry acidified sausage was manufactured using five different concentrations of Glucono-delta-lactone (GdL), notable 0.5, 1.0, 1.5, 2.0 and 3.0%. All of the treatments pHu differed (P<0.05) from one another, although, only 1.5, 2.0 and 3.0% were below 5.0. Water activity aW, mass loss and hardness also differed (P<0.05) where 2.0 and 3.0% had the lowest aW, the highest mass loss and highest hardness values. Microbiologically, only 3.0% was safe to consume although 1.5 and 2.0% would suffice if the spice raw material was not contaminated. The choice of 1.5% was considered the optimal concentration in the dry acidified sausage based on the physico-chemical and microbiological results. Kinetic parameters confirmed that heating at 55°C for 65 min released the acidulant from the encapsulate and fully acidified the dry acidified sausage. A brief comparative study between the probe and sodium iodoacetate method of pH measurement was conducted. Similar regressions were developed however, the simpler probe method had a better fit (R2 = 0.9673) compared to (R2 = 0.8944), resulting in the simpler probe method being chosen for the continuation of the study. Further to this, eight concentrations, one through to eight percent, were produced for each of the three encapsulated acidulants. Upon heating to 55°C for 65 min, the sausage batter was acidified. Measurements for pH enabled linear regressions, E-GdL y = -16.81 x + 6.0214 (R2 = 0.9694); E-Lacic acid y = -13.31x + 5.5864 (R2 = 0.9435); E-Citric acid y = -29.536x + 6.0279 (R2 = 0.9844), to be calculated. Validation of the trend lines ensued using a 4 x 6 block design where masses of encapsulated acidulant were weighed out according to the value calculated from the trend line regression equations based on a final pH of 4.8. The optimal GdL concentration of 1.5% was used as a control. Only the GdL treatment pH at 4.9 ± 0.06 was close to the target pH of 4.8. All other treatments differed (P<0.05) from one another and were lower than the target pH; E-GdL = 3.7 ± 0.02, E-Lactic acid = 4.2 ± 0.04 and E-Citric acid = 3.5 ± 0.08. E-citric acid had an apparent crumbly texture which was confirmed by the Max Force 2 (second compression force) value. All the treatments, although well below the required pH, fell in line with the requirements of dried acidified sausage with mass loss > 30% and moisture loss ca. 30%.
An assessment of the potential contribution of micronutrient-enriched food products available from major food retailers to the micronutrient intake of South African adolescents
(Stellenbosch : Stellenbosch University, 2022-04) Barkhuysen, Janine; Sigge, G. O.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
ENGLISH ABSTRACT: Recent global actions have brought attention to health and nutrition issues facing adolescents and the need to address adolescent malnutrition in all its forms. Malnutrition may include under- or overnutrition, and micronutrient deficiencies or excesses. Micronutrient fortification and enrichment of food products can assist in the prevention of micronutrient deficiencies. However, to protect against other forms of malnutrition, the healthfulness or nutritional quality of these food products should also be considered. Micronutrient-enriched food products are available in South Africa. However, limited information is available on the extent of micronutrient-enrichment and the potential of these food products to contribute to adolescent intake of micronutrients without adding to the burden of overnutrition and the risk of multiple non-communicable diseases (NCDs) later in life. This research assignment aims to add to the knowledge base in this area by assessing the potential contribution of micronutrient-enriched food products available in South Africa to the diet of adolescents. A cross-sectional study of the South African micronutrient-enriched packaged food and beverage supply during a three-month period (July to September) in 2021, was used to assess the potential contribution of these food products to the diet of adolescents in terms of micronutrient content and healthfulness. Primary data (involving ingredient lists and nutritional information) was collected online from the main food retailers in South Africa. The micronutrient-enriched food products were tabulated and categorised according to the Nutrient Profile Model for the World Health Organization African Region. A total of 422 food products were found to be enriched with vitamins and/or minerals. The beverage category had the most micronutrient-enriched food products in this study (46%), followed by the breakfast cereals category (24%). Vitamins were most frequently added, led by vitamin A (55% of micronutrient- enriched food products). Minerals were added less frequently, with iron being the most frequently added mineral (26% of micronutrient-enriched food products). The breakfast cereals category had the greatest range of enrichment, with some food products enriched with 13 vitamins (A, B1, B2, B3, B5, B6, B7, B9, B12, C, D, E and K) and eight minerals (calcium, chromium, iron, iodine, magnesium, phosphorus, selenium, and zinc). Micronutrient-enrichment levels varied between the food products, but most of the levels were high enough for South African nutrient content label claims. This indicates that the micronutrient-enriched food products in this study could potentially contribute towards the daily intake of micronutrients by adolescents. However, only 9.5% of the micronutrient-enriched food products are suitable for inclusion in a healthy diet for adolescents, as the rest may contribute towards the burden of overweight and diet-related NCDs. This presents a valuable opportunity to the South African food industry for product reformulation to contribute to the health and nutrition of adolescents.

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