Search Results (17)

The present study adopted a response surface methodology (RSM) approach validated by artificial neural network (ANN) models to optimise the production of a bitter gourd-grape beverage. Aset of statistically pre-designed experiments were conducted, and the RSM optimisation model fitted to the obtained data, yielding adequately fit models for the monitored control variables R² values for alcohol (0.79), pH (0.89), and total soluble solids (TSS) (0.89). Further validation of the RSM model fit using ANN showed relatively high accuracies of 0.98, 0.88, and 0.82 for alcohol, pH, and TSS, respectively, suggesting satisfactory predictability and adequacy of the models. A clear effect of the optimised conditions, namely fermentation time at (72 h), fermentation temperature (32.50 and 45.11 °C), and starter culture concentration (3.00 v/v) on the total titratable acidity (TTA), was observed with an R² value of (0.40) and RSM model fit using ANN overall accuracy of (0.56). However, higher TTA values were observed for samples fermented for 72 h at starter culture concentrations above 3 mL. The level of 35% bitter gourd juice was optimised in this study and was considered desirable because the goal was to make a low-alcohol beverage. Full article

This study evaluated the impact of seasonal and geographical variations on the toxigenicity of Aspergillus and Fusarium strains previously isolated from smallholder dairy cattle feeds and feedstuffs sampled during summer and winter in the Free State and Limpopo provinces of South Africa (SA). In total, 112 potential toxigenic fungal species were obtained and determined for their capability to produce mycotoxins on solid Czapek Yeast Extract Agar (CYA); followed by liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Our result revealed that 41.96% of the fungal species produced their respective mycotoxins, including aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), and zearalenone (ZEN), with higher levels of AFB₁ (0.22 to 1045.80 µg/kg) and AFB₂ (0.11 to 3.44 µg/kg) produced by fungal species isolated from summer samples than those in winter [(0.69 to 14.44 µg/kg) and (0.21 to 2.26 µg/kg), respectively]. The same pattern was also observed for AFB₁ and AFB₂ in Limpopo (0.43 to 1045.80 µg/kg and 0.13 to 3.44 µg/kg) and Free State (0.22 to 576.14 µg/kg and 0.11 to 2.82 µg/kg), respectively. More so, ZEN concentrations in summer (7.75 to 97.18 µg/kg) were higher than in winter (5.20 to 15.90 µg/kg). A similar observation was also noted for ZEN in Limpopo (7.80 to 97.18 µg/kg) and Free State (5.20 to 15.90 µg/kg). These findings were confirmed via Welch and Brown-Forsythe tests with significantly (p ≤ 0.05) higher mycotoxin levels produced by fungal strains obtained in samples during summer than those in winter. In contrast, the concentrations of mycotoxins produced by the fungal species from both provinces were not significantly (p > 0.05) different. Full article

Mahweu is an important indigenous beverage for many low-income and undernourished consumers in southern Africa. As a result, the nutritional and phytochemical profile of mahewu samples (obtained using optimized fermentation and boiling conditions from a previous study) as well as their related raw materials (white and yellow maize) were investigated. At these conditions, white and yellow maize mahewu (WM and YM) were prepared utilizing various inocula including sorghum malt, wheat, millet malt, or maize malt, and the pH, titratable acidity (TTA), total soluble solid (TSS), and proximate analysis were determined. The mineral content, amino acid composition, and phenolic compound profile were also investigated using inductive coupled plasma optical emission spectrometry (ICP-OES), high-performance liquid chromatography (HPLC), and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS), respectively. Fermentation was observed to have influenced the proximate composition of obtained mahewu samples compared to the raw flour with significant (p ≤ 0.05) improvement in protein from 8.59 to 9.7% (YM) and 8.78 to 9% (WM) as well as carbohydrate from 72.27 to 74.47% (YM) and 71.15 to 72.65% (WM). Sodium, magnesium, phosphorous, potassium, calcium, manganese, iron, copper, and zinc were the minerals detected in the mahewu samples, while potassium was the most abundant mineral, having values ranging from 3051.61 to 3283.38 mg/kg (YM) and 2882.11 to 3129.97 mg/kg (WM). Heavy metals detected in this study were all below the recommended tolerable levels by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Arginine and leucine with values ranging from 0.47 to 0.52 g/100 g (YM) and 0.48 to 0.53 g/100 g (WM) as well as 0.91 to 1.04 g/100 g (YM) and 0.95 to 1.01 g/100 g (WM), respectively, were the most abundant essential amino acids, whereas for non-essential amino acids, glutamic acid, aspartic acid, alanine, and proline were observed to be abundant. Based on the different inocula, the derived mahewu samples prepared using either white or yellow maize have varying nutritional and health beneficial components and the choice of inocula might still be determined by consumer preference. Full article

Mahewu is a fermented food product from maize, commonly consumed in Southern Africa. This study investigated the effect of optimizing fermentation (time and temperature) and boiling time of white maize (WM) and yellow maize (YM) mahewu, with the use of the Box–Behnken-response surface methodology (RSM). Fermentation time and temperature as well as boiling time were optimized and pH, total titratable acidity (TTA) and total soluble solids (TSS) determined. Results obtained showed that the processing conditions significantly (p ≤ 0.05) influenced the physicochemical properties. pH values of the mahewu samples ranged between 3.48–5.28 and 3.50–4.20 for YM mahewu and WM mahewu samples, respectively. Reduction in pH values after fermentation coincided with an increase in TTA as well as changes in the TSS values. Using the numerical multi-response optimisation of three investigated responses the optimal fermentation conditions were observed to be 25 °C for 54 h and a boiling time of 19 min for white maize mahewu and 29 °C for 72 h and a boiling time of 13 min for yellow maize mahewu. Thereafter white and yellow maize mahewu were prepared with the optimized conditions using different inocula (sorghum malt flour, wheat flour, millet malt flour or maize malt flour) and the pH, TTA and TSS of the derived mahewu samples determined. Additionally, amplicon sequencing of the 16S rRNA gene was used to characterise the relative abundance of bacterial genera in optimized mahewu samples, malted grains as well as flour samples. Major bacterial genera observed in the mahewu samples included Paenibacillus, Stenotrophomonas, Weissella, Pseudomonas, Lactococcus, Enterococcus, Lactobacillus, Bacillus, Massilia, Clostridium sensu stricto 1, Streptococcus, Staphylococcus, Sanguibacter, Roseococcus, Leuconostoc, Cutibacterium, Brevibacterium, Blastococcus, Sphingomonas and Pediococcus, with variations noted for YM mahewu and WM mahewu. As a result, the variations in physicochemical properties are due to differences in maize type and modification in processing conditions. This study also discovered the existence of variety of bacterial that can be isolated for controlled fermentation of mahewu. Full article

This study investigated the effect of fermentation conditions (time and temperature) on the nutritional composition and health-promoting properties of raw milk, optimized naturally fermented amasi, and amasi fermented with starter culture. The composition of the products, including chemical analysis, amino acids, mineral composition, and fatty acids, as well as health-promoting properties (total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity assays (2,2-Azinobis (3-Ethyl-Benzothiazone-6-Sulphonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH)) were investigated. The results showed that the fermentation conditions (time and temperature) significantly affected the ash contents of both fermented samples. Fermentation was also observed to have increased the contents of most of the essential and non-essential amino acids. A high concentration of glutamic acid was observed in optimized naturally fermented amasi at 32 °C (OP32, 6.30 g/100 g), followed by starter-culture-fermented amasi at 25 °C (SC25, 5.58 g/100 g) and then starter-culture-fermented amasi at 32 °C (SC32, 5.35 g/100 g), with optimized naturally fermented amasi at 32 °C (OP25, 4.46 g/100 g) having the lowest concentration. A similar trend in the composition of minerals was also observed, with potassium being the most abundant (110.1–134.5 µg/g). The TPC, TFC, and the antioxidant activities were significantly improved by fermentation, while a significant reduction in free fatty acids was recorded. In conclusion, the fermentation conditions had a significant effect on the nutritional and health-promoting properties of amasi. The results provided in this study could provide nutritional information regarding the composition of amasi, which can be beneficial to produce a high-quality product. Full article

Bitter gourd beverages are well acclaimed for their health benefits, which have propelled their consumption. The beverages are prepared through a fermentation process, which is one of the oldest means of preserving and enhancing the flavour of many foods. Optimized conditions for the fermentation of a bitter gourd–grape beverage were investigated in our previous study. In the present study, a statistical comparison (one-way analysis of variance (ANOVA), Tukey’s honestly significant difference (HSD) test and an independent t-test)) of grape juice, bitter gourd juice and the fermented bitter gourd–grape beverage (with and without enzymes) was carried out to find significant differences among the products. Alcohol was found to be consistent for the four products with p > 0.05, whereas significant differences (p ≤ 0.05) in the pH, antioxidant activity (ferric reducing antioxidant assay (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS)), total titratable acidity (TTA), total soluble solids (TSS), total flavonoid content (TFC) and total phenolic content (TPC) were observed. The fermented bitter gourd–grape beverage (FBGGB) with enzymes had the highest antidiabetic potential content (27.07). The data obtained demonstrate that fermentation indeed enhances the biochemical function of vegetables (in this case, bitter gourd) and could thus be considered for the commercial processing of bitter gourd. Full article

Fermented food products, especially those derived from cereals and legumes are important contributors to diet diversity globally. These food items are vital to food security and significantly contribute to nutrition. Fermentation is a process that desirably modifies food constituents by increasing the palatability, organoleptic properties, bioavailability and alters nutritional constituents. This review focuses on deciphering possible mechanisms involved in the modification of nutritional constituents as well as nutrient bioavailability during the fermentation of cereals and legumes, especially those commonly consumed in developing countries. Although modifications in these constituents are dependent on inherent and available nutrients in the starting raw material, it was generally observed that fermentation increased these nutritive qualities (protein, amino acids, vitamins, fats, fatty acids, etc.) in cereals and legumes, while in a few instances, a reduction in these constituents was noted. A general reduction trend in antinutritional factors was also observed with a corresponding increase in the nutrient bioavailability and bioaccessibility. Notable mechanisms of modification include transamination or the synthesis of new compounds during the fermentation process, use of nutrients as energy sources, as well as the metabolic activity of microorganisms leading to a degradation or increase in the level of some constituents. A number of fermented products are yet to be studied and fully understood. Further research into these food products using both conventional and modern techniques are still required to provide insights into these important food groups, as well as for an overall improved food quality, enhanced nutrition and health, as well as other associated socioeconomic benefits. Full article

The aim of this present study was to optimize the fermentation conditions (time and temperature) of amasi (a Southern African fermented dairy product) using response surface methodology (RSM), and to determine the physicochemical properties, as well as the microbial composition, using next generation sequencing. Fermentation time and temperature were optimized to produce different amasi samples and different parameters, including pH, total soluble solids (TSS), total titratable acids (TTA), and consistency. All the variables studied were found to show significant (p ≤ 0.05) changes with increasing fermentation time and temperature. Numerical optimization was used to obtain the optimal fermentation conditions for amasi; based on RSM, it was 32 °C for 140 h, while with k-means clustering, it was 25 °C for 120 h. Under both conditions for the optimal samples, the pH reduced from 6.64 to 3.99, TTA increased from 0.02 to 0.11 (% lactic acid), TSS decreased from 9.47 to 6.67 °Brix, and the consistency decreased from 23 to 15.23 cm/min. Most of the identified bacteria were linked to lactic acid bacteria, with the family Lactobacillaceae being the most predominant in amasi, while in raw milk, Prevotellaceae was the most abundant. The fermentation conditions (time and temperature) had a significant influence on the parameters investigated in this study. Results of this study could provide information for the commercialization of quality amasi. Full article

This study aimed to investigate the kinetics of phenolic compound modification during the fermentation of maize flour at different times. Maize was spontaneously fermented into sourdough at varying times (24, 48, 72, 96, and 120 h) and, at each point, the pH, titratable acidity (TTA), total soluble solids (TSS), phenolic compounds (flavonoids such as apigenin, kaempferol, luteolin, quercetin, and taxifolin) and phenolic acids (caffeic, gallic, ferulic, p-coumaric, sinapic, and vanillic acids) were investigated. Three kinetic models (zero-, first-, and second-order equations) were used to determine the kinetics of phenolic modification during the fermentation. Results obtained showed that fermentation significantly reduced pH, with a corresponding increase in TTA and TSS. All the investigated flavonoids were significantly reduced after fermentation, while phenolic acids gradually increased during fermentation. Among the kinetic models adopted, first-order (R² = 0.45–0.96) and zero-order (R² = 0.20–0.82) equations best described the time-dependent modifications of free and bound flavonoids, respectively. On the other hand, first-order (R² = 0.46–0.69) and second-order (R² = 0.005–0.28) equations were best suited to explain the degradation of bound and free phenolic acids, respectively. This study shows that the modification of phenolic compounds during fermentation is compound-specific and that their rates of change may be largely dependent on their forms of existence in the fermented products. Full article

Umqombothi (a South African indigenous beer) is an important dietary beverage for many undernourished, low-income consumers in rural, semi-urban and urban areas. Umqombothi was brewed using optimal conditions earlier obtained and compared to the customary beer brew (CB) and mixed raw ingredients (RI). The products were evaluated for proximate compositions, minerals, amino acids, B-group vitamins, and sugar compounds. The optimised beer brew (OPB) was relatively higher in energy (165 kcal), crude protein (8.6%), and ash content (1.0%). The CB had the highest concentration of sodium (299.8 mg/kg), magnesium (1170.5 mg/kg), potassium (2993.8 mg/kg), and phosphorus (2100.7 mg/kg). Glutamic acid was the highest detected amino acid, with concentrations of 1.5 g/100 g, 1.5 g/100 g, and 1.6 g/100 g in the RI, CB, and OPB, respectively. The OPB contained a higher concentration of the two forms of vitamin B₃, nicotinamide (0.2 µg/g) and nicotinic acid (0.7 µg/g) in comparison to the CB. The concentration of the antioxidant, mannitol, was 0.4 mg/g, 0.2 mg/g, and 2.0 mg/g in the RI, CB, and OPB respectively. Overall, OPB displayed a desirable nutritional profile compared to the CB. Full article

Traditional beers, such as palm wine, kombucha and others, are notable beverages consumed all over the globe. Such beverages historically contribute to food security on a global scale. Umqombothi is a South African traditional beer nutritionally packed with minerals, amino acids, B-group vitamins and much-needed calories. As a result, the production and consumption of this traditional beverage has been an integral part of South African’s social, economic and cultural prosperity. Unfortunately, difficulties in bioprocessing operations have limited its availability to household and small-scale production. It is at these micro-production scales that poor hygiene practices and the use of hazardous additives and contaminated raw materials continue to increase, posing serious health risks to the unassuming consumer. This study provides an overview of the processing steps and underlying techniques involved in the production of umqombothi, while highlighting the challenges as well as future developments needed to further improve its quality and global competitiveness with other alcoholic products. Full article

Strychnos madagascariensis Poir is an underutilized fruit that is considered a valuable food during droughts and famine. The aim of this research was to characterize the nutritional composition and the flour functional properties, for the use as a potential food source. Seed flour was analysed using a standard enzymatic assay for sugars, acid/neutral detergent analysis for fibre, ether extraction for fat and HPLC for strychnine. Results showed that the seeds contained 41% reducing sugars and 53% fibre. The mineral composition, determined using microwave-assisted acid digestion and inductively coupled plasma optical emission spectrometry (ICP–OES), showed that the seeds contained high quantities of iron (15.78 mg/100 g) and manganese (9.86 mg/100 g). The flour water absorption index (1.37 g/g) was substantially higher than that of wheat, brown rice and tapioca flours and the oil absorption index showed similarities to the reference flours (1.09 g/g). The flour peak (37,788 RVU) and final viscosities (62,928 RVU) were significantly (p < 0.001) higher than the reference flours. This study was the first to quantify the strychnine content (0.08%) in the seeds. Results suggest that the seeds have good potential for food product development; however, further processing is essential to ensure safety for consumption. Full article

Efforts to attain sustainable nutritional diets in sub-Saharan Africa (SSA) are still below par. The continent is envisaged to face more impending food crises. This review presents an overview of common edible insects in Africa, their nutritional composition, health benefits and utilization in connection with fermentation to enrich the inherent composition of insect-based products and offer foods related to existing and generally preferred culinary practice. Attempts to explore fermentation treatments involving insects showed fermentation affected secondary metabolites to induce antimicrobial, nutritional and therapeutic properties. Available value-added fermented edible insect products like paste, powder, sauces, and insect containing fermented foods have been developed with potential for more. Novel fermented edible insect-based products could effectively fit in the continent’s food mix and therefore mitigate ongoing food insecurity, as well as to balance nutrition with health risk concerns limiting edible insects’ product acceptability in SSA. Full article

Sorghum (Sorghum bicolor) is a well-known drought and climate resistant crop with vast food use for the inhabitants of Africa and other developing countries. The importance of this crop is well reflected in its embedded benefits and use as a staple food, with fermentation playing a significant role in transforming this crop into an edible form. Although the majority of these fermented food products evolve from ethnic groups and rural communities, industrialization and the application of improved food processing techniques have led to the commercial success and viability of derived products. While some of these sorghum-based fermented food products still continue to bask in this success, much more still needs to be done to further explore evolving techniques, technologies and processes. The addition of other affordable nutrient sources in sorghum-based fermented foods is equally important, as this will effectively augment the intake of a nutritionally balanced product. Full article

Urbanization, emergence, and prominence of diseases and ailments have led to conscious and deliberate consumption of health beneficial foods. Whole grain (WG) cereals are one type of food with an array of nutritionally important and healthy constituents, including carotenoids, inulin, β-glucan, lignans, vitamin E-related compounds, tocols, phytosterols, and phenolic compounds, which are beneficial for human consumption. They not only provide nutrition, but also confer health promoting effects in food, such as anti-carcinogenic, anti-microbial, and antioxidant properties. Fermentation is a viable processing technique to transform whole grains in edible foods since it is an affordable, less complicated technique, which not only transforms whole grains but also increases nutrient bioavailability and positively alters the levels of health-promoting components (particularly antioxidants) in derived whole grain products. This review addresses the impact of fermentation on phenolic compounds and antioxidant activities with most available studies indicating an increase in these health beneficial constituents. Such increases are mostly due to breakdown of the cereal cell wall and subsequent activities of enzymes that lead to the liberation of bound phenolic compounds, which increase antioxidant activities. In addition to the improvement of these valuable constituents, increasing the consumption of fermented whole grain cereals would be vital for the world’s ever-growing population. Concerted efforts and adequate strategic synergy between concerned stakeholders (researchers, food industry, and government/policy makers) are still required in this regard to encourage consumption and dispel negative presumptions about whole grain foods. Full article