Research Articles (Food Science)
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- ItemAdvances in design and performance evaluation of fresh fruit ventilated distribution packaging : a review(Publishers version, 2020-02-17) Mukama, Matia; Ambaw, Alemayehu; Opara, Umezuruike LinusThis 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.
- ItemApplication 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.
- ItemAspalathin-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, JohanWe 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.
- ItemAspalathin-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.
- ItemChanges in the phenolic composition and antioxidant activity of pinotage, cabernet sauvignon, chardonnay and chenin blanc wines during bottle ageing(South African Society for Enology and Viticulture, 2005) De Beer, D.; Joubert, E.; Gelderblom, W. C. A.; Manley, M.The effect of bottle ageing on the antioxidant activity of Pinotage, Cabernet Sauvignon, Chardonnay and Chenin blanc wines, using the 2,2'-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation (ABTS•+) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH0) scavenging assays, was determined. Storage at 0°C, 15°C or 30°C for a period of 12 months resulted in a significant (p ≤ 0.05) decrease in both the total antioxidant activity (TAAAnTs and TAAoPPH) and the total phenol content of the wines. The antioxidant potency of the total phenols of most of the wines, which is a ratio of antioxidant activity to the total phenol content, also decreased. The total anthocyanins in the red wines decreased significantly (p ≤ 0.05) over 12 months except for storage at 0°C, while the flavanol content of the Pinotage, Cabernet Sauvignon and Chardonnay wines increased up to nine months storage with a subsequent decrease to 12 months. The flavonol content of all the wines decreased, while only minor changes in their hydroxycinnamate content were observed during the storage period. Understanding the complexity of these reactions may provide clues for stabilising especially red wines to preserve the antioxidant activity without losing the beneficial effects of colouring and flavour development during bottle ageing.
- ItemCharacterisation of pinotage wine during maturation on different oak products(SASEV, 2008-01) De Beer, D.; Joubert, E.; Marais, J.; Du Toit, W.; Fourie, B.; Manley, M.The effect of oak contact on the phenolic composition, total antioxidant capacity (TAC) and colour of Pinotage wines was investigated during maturation. Oak maturation included traditional treatments, such as new, second-fill and third-fill barrels, as well as alternative treatments (oak chips, staves, extract and dust) applied in old barrels over a period of 28 weeks. Oak maturation using traditional and alternative treatments improved the objective colour of Pinotage wine by decreasing the L* value. Losses in TAC caused by decreased concentrations of monomeric phenolic compounds (most anthocyanins, flavan-3-ols, flavonols and hydroxycinnamic acids) during oak maturation were negated by increased concentrations of gallic acid and the formation of new oligomeric and polymeric pigments. Wine maturation in stainless steel containers also resulted in a decrease in anthocyanin content. The decrease in phenolic acid content for wines matured in stainless steel was less pronounced, while their flavan-3-ol content remained stable. The new-barrel treatment had the most pronounced effect on all parameters. Oak maturation can be used for the production of Pinotage wine when the retention of TAC is a high priority.
- ItemCharacterization of volatiles and aroma-active compounds in honeybush (Cyclopia subternata) by GC-MS and GC-O analysis(American Chemical Society, 2012-03) Le Roux, Maritha.; Cronje, J. Christel; Burger, B. V.; Joubert, ElizabethVolatile organic compounds (VOCs) in fermented honeybush, Cyclopia subternata, were sampled by means of a high-capacity headspace sample enrichment probe (SEP) and analyzed by gas chromatography-mass spectrometry (GC-MS). Stereochemistry was determined by means of enantioselective GC-MS with derivatized β-cyclodextrin columns as chiral selectors. A total of 183 compounds, the majority of which are terpenoids (103; 56%), were identified by comparing their mass spectra and retention indices with those of reference compounds or tentatively identified by comparison with spectral library or literature data. Of these compounds, 37 were determined by gas chromatography-olfactometry (GC-O), using detection frequency (DF) and aroma extract dilution analysis (AEDA), to be odor-active (FD ≥ 2). (E)-β-Damascenone, (R/S)-linalool, (E)-β-damascone, geraniol, (E)-β-ionone, and (7E)-megastigma-5,7,9-trien-4-one were identified with the highest FD factors (≥512). The odors of certain compounds, that is, (6E,8Z)-megastigma-4,6,8-trien-3-one, (6E,8E)-megastigma-4,6,8-trien-3-one, (7E)-megastigma-5,7,9-trien-4-one, 10-epi-γ-eudesmol, epi-α- muurolol, and epi-α-cadinol, were perceived by GC-O assessors as typically honeybush-like. © 2012 American Chemical Society.
- ItemChemical characterization of the constituents of the aroma of honeybush, Cyclopia genistoides(Elsevier, 2008-01) Le Roux, M.; Cronje, J. C.; Joubert, E.; Burger, B. V.A high-capacity headspace sample enrichment probe (SEP) was used in conjunction with gas chromatography-mass spectrometry (GC-MS) to analyse the volatile organic compounds present in the aroma of dry or infused, unfermented (green) and fermented C. genistoides, one of the South African Cyclopia species from which a herbal tea, known as honeybush tea, is made. Seventy-seven compounds were identified in the volatile fraction of the aroma of dry, green C. genistoides, comprising, inter alia, a large number of saturated and unsaturated alcohols, aldehydes and methyl ketones. In the aroma of dry, as well as infused, fermented C. genistoides, 79 compounds were identified, 46 of which were terpenoids that were mostly present in much lower relative concentrations in the unfermented material. The methodology developed and the results obtained in the analysis of the aroma of C. genistoides provide a basis for ongoing comparative studies on the chemical composition of a series of prominent Cyclopia species with the view to developing a rapid screening device and protocol for honeybush tea evaluation. © 2007 SAAB.
- ItemComparative genomics of Fructobacillus spp. and Leuconostoc spp. reveals nichespecific evolution of Fructobacillus spp.(BioMed Central, 2015) Endo, Akihito; Tanizawa, Yasuhiro; Tanaka, Naoto; Maeno, Shintaro; Kumar, Himanshu; Shiwa, Yuh; Okada, Sanae; Yoshikawa, Hirofumi; Dicks, Leon Milner Theodore, 1961-; Nakagawa, Junichi; Arita, MasanoriBackground: Fructobacillus spp. in fructose-rich niches belong to the family Leuconostocaceae. They were originally classified as Leuconostoc spp., but were later grouped into a novel genus, Fructobacillus, based on their phylogenetic position, morphology and specific biochemical characteristics. The unique characters, so called fructophilic characteristics, had not been reported in the group of lactic acid bacteria, suggesting unique evolution at the genome level. Here we studied four draft genome sequences of Fructobacillus spp. and compared their metabolic properties against those of Leuconostoc spp. Results: Fructobacillus species possess significantly less protein coding sequences in their small genomes. The number of genes was significantly smaller in carbohydrate transport and metabolism. Several other metabolic pathways, including TCA cycle, ubiquinone and other terpenoid-quinone biosynthesis and phosphotransferase systems, were characterized as discriminative pathways between the two genera. The adhE gene for bifunctional acetaldehyde/alcohol dehydrogenase, and genes for subunits of the pyruvate dehydrogenase complex were absent in Fructobacillus spp. The two genera also show different levels of GC contents, which are mainly due to the different GC contents at the third codon position. Conclusion: The present genome characteristics in Fructobacillus spp. suggest reductive evolution that took place to adapt to specific niches.
- ItemComprehensive phenolic profiling of Cyclopia genistoides (L.) Vent. by LC-DAD-MS and -MS/MS reveals novel xanthone and benzophenone constituents(MDPI, 2014-08) Beelders, Theresa; De Beer, Dalene; Stander, Maria A.; Joubert, ElizabethA high-performance liquid chromatographic (HPLC) method coupled with diode-array detection (DAD) was optimized for the qualitative analysis of aqueous extracts of Cyclopia genistoides. Comprehensive insight into the phenolic profile of unfermented and fermented sample extracts was achieved with the identification of ten compounds based on comparison with authentic reference standards and the tentative identification of 30 additional compounds by means of electrospray ionization mass spectrometry (ESI-MS) and tandem MS detection. Three iriflophenone-di-O,C-hexoside isomers, three xanthone-dihydrochalcone derivatives and one dihydrochalcone are herein tentatively identified for the first time in C. genistoides. Of special interest is one iriflophenone-di-O,C-hexoside present in large amounts. New compounds (tentatively) identified for the first time in this species, and also in the genus Cyclopia, include two aromatic amino acids, one flavone, an iriflophenone-di-C-hexoside, a maclurin-di-O,C-hexoside, two tetrahydroxyxanthone-C-hexoside isomers, a tetrahydroxyxanthone-di-O,C-hexoside, two symmetric tetrahydroxyxanthone-C-hexoside dimers, nine glycosylated flavanone derivatives and five glycosylated phenolic acid derivatives. The presence of new compound subclasses in Cyclopia, namely aromatic amino acids and glycosylated phenolic acids, was demonstrated. The HPLC-DAD method was successfully validated and applied to the quantitative analysis of the paired sample extracts. In-depth analysis of the chemical composition of C. genistoides hot water extracts gave a better understanding of the chemistry of this species that will guide further research into its medicinal properties and potential uses.
- ItemThe contribution of wildlife to sustainable natural resource utilization in Namibia : a review(MDPI - Multidisciplinary Digital Publishing Institute, 2010-11-15) Van Schalkwyk, Diana L.; McMillin, Kenneth W.; Witthuhn, R. Corli; Hoffman, Louw C.Namibia is the driest country in sub-Saharan Africa, but well known for its richness in species and sustainable natural resource utilization. The Namibian farming sector consists mainly of extensive farming systems. Cattle production contributes 54% of the livestock sector’s production output, followed by sheep and goats (25%), hides and skins (9%), and other forms of agricultural production (12%). Namibia’s freehold farmers have obtained ownership rights over land and livestock since the early 1900s; commercial rights over wildlife and plants were given to freehold farmers in 1967 and to communal farmers in 1996. Natural resource-based production systems then overtook agricultural production systems and exceeded it by a factor of at least two. The shift from practicing conservation to sustainable utilization of natural resources contributed to the rapid growth of wildlife utilization. The wildlife industry in Namibia is currently the only animal production system that is expanding. There are in total at least two million head of different wildlife species. The broader impact of the utilization of wildlife on the economy is estimated to be around N$ 1.3 billion. Tourism, live sales and trophy hunting, cannot sustain further growth. Wildlife farming could offer better opportunities for ensuring long-term sustainability. As the game meat trade in Namibia is not formalized, harvesting wildlife to satisfy the demand for game meat in export markets is still in its infancy. Sustainable harvesting of wildlife for meat production, however, has the potential to increase earnings to the beneficiaries in the wildlife sector.
- ItemDeriving a grain hardness calibration for Southern and Western Cape ground wheat samples by means of Fourier transform near infrared (FT-NIR) spectroscopy(2001) Manley, M.; Van Zyl, L.; Osborne, B.Please see full-text for abstract.
- ItemDevelopment of chemical-based reference standards for rooibos and honeybush aroma lexicons(Elsevier, 2019) Du Preez, B. V. P.; De Beer, D.; Moelich, E. I.; Muller, M.; Joubert, E.The honeybush sensory wheel was revised, using a large sample set (n = 585) comprising of the major commercial Cyclopia species, i.e. C. intermedia, C. subternata and C. genistoides. Only positive and negative aroma attributes were included in the wheel. Chemicals were identified to serve as reference standards for the honeybush (Cyclopia spp.) lexicon. Similarly, chemical-based reference standards were identified for the rooibos (Aspalathus linearis) lexicon. From a comprehensive literature search and gas chromatography–mass spectrometry analyses, chemicals were screened by an expert panel for their suitability in terms of typicality of the target aroma. Each chemical was evaluated in a ‘base tea’ and compared to a specific ‘reference tea’ exhibiting a high intensity of the target aroma. A total of 30 and 44 chemicals for rooibos and honeybush, respectively, were selected for validation by a trained panel. Descriptive sensory analysis was conducted to assign typicality and intensity scores for each chemical representing a target aroma attribute. Several chemicals were identified as suitable reference standards for the following aroma notes: isophorone (‘rooibos-woody’), maltyl isobutyrate (‘caramel’), cis-3-hexenol (‘green grass’), 4-oxoisophorone (‘seaweed’) and 2,4,6-trichloroanisole (‘musty/mouldy’) for rooibos; and 2-acetyl-5-methylfuran (‘woody’), levulinic acid (‘fynbos-sweet’), maltyl isobutyrate (‘caramel’), and 2-acetylpyrrole (‘nutty’) for honeybush.
- ItemDifferential modulation of gene expression encoding hepatic and renal xenobiotic metabolizing enzymes by an aspalathin-enriched rooibos extract and aspalathin(Thieme Gruppe, 2019) Abrahams, Sameega; Samodien, Sedicka; Lilly, Mariska; Joubert, Elizabeth; Gelderblom, WentzelModulation of the expression of hepatic and renal genes encoding xenobiotic metabolizing enzymes by an aspalathin-enriched green rooibos (Aspalathus linearis) extract (GRE) was investigated in the liver and kidneys of F344 rats following dietary exposure of 28 d, as well as selected xenobiotic metabolizing genes in rat primary hepatocytes. In the liver, GRE upregulated genes (p < 0.05) encoding aldehyde dehydrogenase, glucose phosphate isomerase, and cytochrome P450 while 17β-hydroxysteroid dehydrogenase 2 (Hsd17β2) was downregulated. In primary hepatocytes, GRE lacked any effect, while aspalathin downregulated Hsd17β2, mimicking the effect of GRE in vivo, and upregulated catechol-O-methyl transferase and marginally (p < 0.1) cytochrome P450 2e1. In the kidneys, GRE upregulated (p < 0.05) genes encoding the phase II xenobiotic metabolism enzymes, glutathione-S-transferase mµ and microsomal glutathione-S-transferase, while downregulating genes encoding the ATP binding cassette transporter, cytochrome P450, gamma glutamyltransferase 1, and N-acetyltransferase 1. Differential modulation of the expression of xenobiotic metabolizing genes in vivo and in vitro by GRE is dose-related, duration of exposure, the tissue type, and interactions between specific polyphenol and/or combinations thereof. Aspalathin is likely to be responsible for the downregulation of estradiol and testosterone catabolism by GRE in the liver. The differential gene expression by GRE in the liver and kidneys could, depending on the duration exposure and dose utilized, determine the safe use of such an extract in humans for specific health and/or disease outcomes.
- ItemDiscriminating muscle type of selected game species using near infrared (NIR) spectroscopy(Elsevier, 2019-11-02) Dumalisile, Pholisa; Manley, Marena; Hoffman, LouwrensIn this study near infrared (NIR) spectroscopy was used to discriminate between different muscle types within each species of selected game animals, and to classify species regardless of the muscle. Muscle steaks from longissimus thoracis et lumborum (LTL) located at the 6th rib of the carcasses, infraspinatus (IS) and supraspinatus (SS) located on the forequarter, and biceps femoris (BF), semitendinosus (ST) and semimembranosus (SM) located on the hindquarter of impala and eland species; and samples from fan fillet (FF), big drum (BD), triangle steak (TS), moon steak (MS) and rump steak (RS) of ostrich species were scanned with a handheld NIR spectrophotometer in the spectral range of 908–1700 nm. Spectra were pre-treated with different pre-processing methods and classification models were developed using partial least squares discriminant analysis (PLS-DA). Classification accuracies were higher when the muscles were grouped according to their anatomical location in the carcass, than attempting to classify them separately. Classification accuracies ranging from 85.0 to 100% were achieved throughout, with forequarter muscles yielding the highest classification accuracy rate for both impala and eland species. Furthermore, when the species were discriminated regardless of muscles, PLS-DA models pre-treated with SNV-Detrend and Savitzky-Golay 1st derivative yielded accuracies of 97, 81 and 92% for eland, impala and ostrich, respectively. These results indicate that NIR spectroscopy can be used for the authentication of game meat, specifically impala, eland and ostrich. Furthermore, it was easier to discriminate species regardless of the muscle used than different muscles within each species.
- ItemEffect of colony age on near infrared hyperspectral images of foodborne bacteria(IM Publications, 2019-01-30) Williams, Paul J.; Kammies, Terri-Lee; Gouws, Pieter A.; Manley, MarenaNear infrared hyperspectral imaging (NIR-HSI) and multivariate image analysis were used to distinguish between foodborne pathogenic bacteria, Bacillus cereus, Escherichia coli, Salmonella Enteritidis, Staphylococcus aureus and a non-pathogenic bacterium, Staphylococcus epidermidis. Hyperspectral images of bacteria, streaked out on Luria—Bertani agar, were acquired after 20 h, 40 h and 60 h growth at 37 °C using a SisuCHEMA hyperspectral pushbroom imaging system with a spectral range of 920–2514 nm. Three different pre-processing methods: standard normal variate (SNV), Savitzky—Golay (1stderivative, 2nd order polynomial, 15-point smoothing) and Savitzky—Golay (2nd derivative, 3rd order polynomial, 15-point smoothing) were evaluated. SNV provided the most distinct clustering in the principal component score plots and was thus used as the sole pre-processing method. Partial least squares discriminant analysis (PLS-DA) models were developed for each growth period and was tested on a second set of plates, to determine the effect the age of the colony has on classification accuracies. The highest overall prediction accuracies where test plates required the least amount of growth time, was found with models built after 60 h growth and tested on plates after 20 h growth. Predictions for bacteria differentiation within these models ranged from 83.1 % to 98.8 % correctly predicted pixels.
- ItemEffect of different combinations of freezing and thawing rates on the shelf-life and oxidative stability of ostrich moon steaks (M. Femorotibialis medius) under retail display conditions(MDPI, 2020) Leygonie, Coleen; Hoffman, Louwrens ChristiaanThe aim of this study was to investigate the interaction between different rates of freezing and thawing on whole ostrich moon steaks to establish a combination or singular main effect that minimises thaw loss and maximises the retail display shelf-life regarding moisture loss, colour, lipid oxidation and tenderness. Five characteristic freezing rates (FR: 1, 2, 4, 8, 24 h) were compared with five characteristic thawing rates (TR: 1.5, 3, 6.5, 14, 21 h) in a completely randomised block design. Moon steaks (M. femorotibialis medius) from 125 birds were randomly assigned to a specific treatment combination before being subjected (after thawing) to a 10-day chilled storage at 4 °C shelf-life trial. Thawing rate had no effect (p > 0.05) on any of the quality (colour, drip and cooking losses, shear force, 2-thiobarbituric acid (TBARS)) parameters whilst freezing rate and display time both had significant (p < 0.05) influences. Thaw loss was lowest (p < 0.05) for the FR_1h and FR_2h, followed by FR_4h, FR_8h and FR_24. The FR_1h had the highest (p < 0.05) drip and shear force values during display while the FR_2h and FR_8h had the highest rate of oxidation (TBARS and metmyoglobin formation). FR_24h had the second best (p < 0.05) colour retention after FR_4h and minimal package drip. Overall, FR_4h resulted in the best quality meat over the entire shelf-life with high bloom retention, low TBARS and shear force, and average thaw, drip and cooking loss.
- ItemEffect of drying on the bioactive compounds, antioxidant, antibacterial and antityrosinase activities of pomegranate peel(BioMed Central, 2016) Mphahlele, Rebogile R.; Fawole, Olaniyi A.; Makunga, Nokwanda P.; Opara, Umezuruike L.The use of pomegranate peel is highly associated with its rich phenolic concentration. Series of drying methods are recommended since bioactive compounds are highly sensitive to thermal degradation. The study was conducted to evaluate the effects of drying on the bioactive compounds, antioxidant as well as antibacterial and antityrosinase activities of pomegranate peel. Methods Dried pomegranate peels with the initial moisture content of 70.30 % wet basis were prepared by freeze and oven drying at 40, 50 and 60 °C. Difference in CIE-LAB, chroma (C*) and hue angle (h°) were determined using colorimeter. Individual polyphenol retention was determined using LC-MS and LC-MSE while total phenolics concentration (TPC), total flavonoid concentration (TFC), total tannins concentration (TTC) and vitamin C concentration were measured using colorimetric methods. The antioxidant activity was measured by radical scavenging activity (RSA) and ferric reducing antioxidant power (FRAP). Furthermore, the antibacterial activity of methanolic peel extracts were tested on Gram negative (Escherichia coli and Klebsiella pneumonia) and Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) using the in vitro microdilution assays. Tyrosinase enzyme inhibition was investigated against monophenolase (tyrosine) and diphenolase (DOPA), with arbutin as positive controls. Results Oven drying at 60 °C resulted in high punicalin concentration (888.04 ± 141.03 mg CE/kg dried matter) along with poor red coloration (high hue angle). Freeze dried peel contained higher catechin concentration (674.51 mg/kg drying matter) + catechin and –epicatechin (70.56 mg/kg drying matter) compared to oven dried peel. Furthermore, freeze dried peel had the highest total phenolic, tannin and flavonoid concentrations compared to oven dried peel over the temperature range studied. High concentration of vitamin C (31.19 μg AAE/g dried matter) was observed in the oven dried (40 °C) pomegranate peel. Drying at 50 °C showed the highest inhibitory activity with the MIC values of 0.10 mg/ml against Gram positive (Staphylococcus aureus and Bacillus subtili. Likewise, the extracts dried at 50 °C showed potent inhibitory activity concentration (22.95 mg/ml) against monophenolase. Principal component analysis showed that the peel colour characteristics and bioactive compounds isolated the investigated drying method. Conclusions The freeze and oven dried peel extracts exhibited a significant antibacterial and antioxidant activities. The freeze drying method had higher total phenolic, tannin and flavonoid concentration therefore can be explored as a feasible method for processing pomegranate peel to ensure retention of the maximum amount of their naturally occurring bioactive compounds.
- ItemEffect of oxygenation during maturation on phenolic composition, total antioxidant capacity, colour and sensory quality of pinotage wine(SASEV, 2008-10) De Beer, D.; Joubert, E.; Marais, J.; Manley, M.The effect of oxygenation on the phenolic composition, total antioxidant capacity (TAC), colour and sensory quality was investigated during the maturation of Pinotage wines. Oxygenation was carried out in discrete monthly doses at two oxygen dosages (2.5 and 5.0 mg O2/L/month) for zero, two, four and six months. Oxygenation at the lower dosage for two months had beneficial effects on the colour and sensory quality of Pinotage wine. The higher oxygen dosage (all times) and longer times (all dosages) had a substantial detrimental effect on the overall sensory quality of the wine. A decrease in the TAC of the wine was observed for all the treatment combinations, despite increased concentrations of gallic acid. During the following harvest, a modified oxygenation treatment, entailing 1.0 mg O2/L in discrete doses every two weeks for two months, was tested. It had little effect on the wine phenolic composition and was not detrimental to the TAC of the wine. The modified oxygenation protocol significantly reduced the berry/ plum intensity of the Pinotage wine without negatively affecting the overall sensory quality. Oxygen addition on a continuous basis may also be less detrimental to the TAC of the wine and provide improved sensory quality.
- ItemEffect of pork rind and soy protein on polony sensory attributes(OMICS International, 2015-01) Mapanda, Crispen; Hoffman, Louwrens C.; Mellett, Francois D.; Muller, NinaThis study determined whether commercially acceptable polony could be manufactured with varying quantities of chicken mechanically recovered meat (MRM), soy flour (S) and pork rind (R). The experimental design used was a two-factor, three-level factorial design, with various soy levels (0%, 4%, 8%) and pork rind (0%, 8%, 16%) resulting in nine treatments (R0S0, R0S4, R0S8, R8S0, R8S4, R8S8, R16S0, R16S4 and R16S8). Five treatment samples, R0S0, R0S4, R0S8, R8S0 and R8S4, which were indicated by the trained panel to have high market potential, were used to determine the degree of liking by consumers. Consumers liked the flavour and texture of treatments R0S0 and R0S4 which were strongly associated with pink colour, firmness and salty taste. Treatments R0S8, R8S0 and R8S4 were preferred less, mainly because they were associated with a perceptible soy flavour, pasty texture and white fat spots. The use of soy flour and pork rind is acceptable at <4% soy and <8% rind.
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