School of Food Technology, Nutrition and Bioengineering (SFTNB) Collections
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ItemIsolation, characterisation and evaluation of selected yeast cultures for tonto production(Makerere University, 2025)Tonto, a traditional Ugandan banana-based alcoholic beverage, is produced through spontaneous fermentation resulting in variable quality and safety. This study investigated the microbial ecology, physicochemical and volatile profiles of traditional Tonto. It also evaluated the effect of selected yeast strains and fermentation strategies on Tonto quality. Spontaneously fermented samples (n = 42) were collected from Ntungamo and Kalungu districts and analysed for their physicochemical composition, volatile compounds, microbial diversity and sensory attributes. Physicochemical analysis revealed significant (p < 0.05) reductions in pH (4.9 ± 0.23 – 3.58 ± 0.32) and total soluble solids (15.01±1.76 – 5.15±0.74 °Brix), an increase in titratable acidity (0.21 ± 0.07 – 0.77± 0.64%) and ethanol content (0.0 – 4.73±1.05%) during fermentation. A total of 38 volatile compounds were identified which were dominated by esters (isoamyl acetate, ethyl butyrate, ethyl caprylate) and higher alcohols. These significantly (p < 0.05) contributed to fruity, floral, and sweet aroma notes. Samples from Ntungamo exhibited significantly higher (p < 0.05) levels of these key volatiles and correspondingly higher consumer acceptability scores compared to those from Kalungu. The most prevalent yeast species isolated from Tonto, were Saccharomyces cerevisiae, Pichia kudriavzevii, Wickerhamomyces anomalus and Hanseniaspora opuntiae, with P. kudriavzevii dominating at later stages of fermentation. Monoculture fermentations of S. cerevisiae y1.7 and P. kudriavzevii y2.4 showed significantly higher (p < 0.05) ethanol yields (4.11 ± 0.12% and 4.30 ± 0.15%, respectively) and ester production compared to other isolates. Principal Component Analysis (PCA) revealed a strong association between yeast and desirable aroma attributes and the rich volatile profile of spontaneously fermented samples. Furthermore, inoculation approach influenced Tonto quality. Sequential co-fermentation of S. cerevisiae y1.7 and P. kudriavzevii y2.4 produced Tonto with significantly higher (p < 0.05), ester concentrations and superior fruity–floral sensory scores while simultaneous co-fermentations yielded higher levels of higher alcohols, phenols, and fatty acids associated with undesirable flavours. Overall, sequential co-fermentation was most suitable for enhancing flavour balance and consumer acceptability. This study demonstrated that S. cerevisiae y1.7 and P. kudriavzevii y2.4 are promising starter culture candidates for improving Tonto quality. The findings provide a foundation for production of starter cultures that can be used in commercial production of Tonto and related traditional beverages
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ItemFood safety knowledge and practices on quality of dressed chicken in Kampala district markets(Makerere University, 2025)In Uganda, the monitoring of safety and quality standards for dressed chicken meat is still limited, raising concerns about consumer health and reducing the market value of the meat. This study set out to investigate how the level of food safety knowledge and handling practices among chicken meat vendors affects the microbial condition of the meat they sell. A targeted selection of traders from key markets in Kampala district was interviewed about their food safety awareness and hygiene behaviors, and samples of their chicken meat were tested for microbial contamination. The study found that men make up the majority of traders (72%). Although many vendors showed moderate to good awareness of food safety, some still lacked understanding of essential practices, especially those related to preventing contamination. Microbial testing revealed that meat from all surveyed markets had bacterial loads above acceptable thresholds. Specifically, Owino Market had the highest levels of total plate count (TPC) and, while Bugolobi Market had samples with the greatest concentration of Staphylococcus species. After introducing a Hazard Analysis and Critical Control Points (HACCP) system to a subset of vendors, the microbial quality of their products improved significantly. This suggests that proper implementation of food safety protocols can lead to cleaner and safer meat. The study highlights the need for ongoing training and awareness efforts targeted at meat processors and vendors. National regulatory bodies like the Uganda National Bureau of Standards (UNBS) should prioritize regular outreach and enforce HACCP-based safety guidelines to ensure that poultry products meet public health and quality standards.
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ItemDevelopment and Preservation of a Starter Culture for Commercial Production of Bongo, a Traditional Fermented Milk Beverage from Uganda.(Makerere University, 2025-11-14)Bongo is a popular traditional fermented milk produced spontaneously, or by backslopping. This predisposes the product to microbial contamination, slow fermentation and variations in product sensory properties. Controlled fermentation using defined starter cultures is vital to address these challenges. Three lactic acid bacteria (LAB) previously isolated based on milk acidification and coagulation, Lacticaseibacillus rhamnosus BM55, Lactococcus lactis BM01 and Leuconostoc pseudomesenteroides BM70 were used in this study to evaluate their potential as starter cultures in fermented cows’ milk. The isolates were evaluated both individually and in combination. Microbial counts, pH, titratable acidity, viscosity, flavour development, syneresis and consumer acceptability were determined using standard methods. The sensory profile of Bongo prepared using the cultures, as well as the spontaneously fermented Bongo, was described using Quantitative Descriptive Analysis (QDA). The relationship between the sensory profile and hedonic scores was determined using preference mapping. The most promising combination of isolates (BM01, BM55 and BM70) was lyophilised in 10% (w/v) skimmed milk and 10% (w/v) soluble starch prior to being stored under refrigeration (4 °C) for 6 months. Survival rate and fermentation characteristics (pH, viscosity, titratable acidity and LAB counts) of Bongo made using the starter culture were determined. The combination of all the three isolates showed the highest potential application as a starter culture with the lowest pH, optimal viscosity, minimal syneresis and enhanced flavour development comparable to that of spontaneously produced Bongo. This was further confirmed by the QDA results. Significant correlations were observed between lumpiness, smoothness and astringency underscoring the importance of the choice of microorganism on the product attributes of Bongo. Texture was the major factor responsible for the differences between the Bongo samples produced by the different starter culture isolates. There was a decline in viability and fermentation ability post lyophilisation and storage because the cryoprotectants do not fully prevent cell damage due to freezing effects and dehydration. LAB lyophilised in skimmed milk showed the highest viability (92%) when compared to LAB lyophilised in soluble starch (78%). Bongo made using LAB lyophilised in skimmed milk had a higher viscosity, lower pH, higher titratable acidity compared to that made with LAB lyophilised in soluble starch implying that skimmed milk had a better protective power. The freeze dried culture maintained acidification ability in the first four months of storage at 4 °C. The mixed starter culture containing Lactococcus lactis BM01; Lacticaseibacillus rhamnosus BM55 and Leuconostoc pseudomesenteroides BM70 lyophilised in 10% (w/v) skimmed milk could be adopted for commercial scale processing of Bongo.
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ItemAcrylamide content of selected processed Ugandan Coffee varieties(Makerere University, 2025)Coffee beans are roasted at high temperatures above 120 oC, which results in a Maillard reaction leading to acrylamide formation. Acrylamide is carcinogenic and causes damage to the nervous and renal systems of the body. The formation of acrylamide in coffee is dependent on factors such as roasting time, temperature, and bean variety. Much as there is a plethora of information regarding acrylamide and its presence in coffee, there still exists a dearth of literature on the effect of processing coffee on acrylamide levels, specifically for coffee varieties grown in Uganda. Therefore, this study assessed the effect of processing on acrylamide levels of selected Ugandan coffee varieties. Coffee cherries of eleven varieties were collected from Luwero district and sun-dried to a moisture content below 12%. The dried coffee cherries were hulled and analyzed for moisture content, screen retention, out-turn, defect count, glucose, fructose, and crude protein contents using standard methods. The coffee beans were then roasted and brewed under different conditions then analyzed for acrylamide using Liquid Chromatography–Mass Spectrometry. The moisture content, defect count, and out turn 2 ranged from 8.7 to 11.0 %, 3.2 to 18.5 %, 81.5 to 96.8 %, and 42.1 to 57.1%, respectively. The overall retention of beans on screen 15 for Kituza Robusta (KR) 6, Kisansa (KS) and Nganda (NG) varieties was above 60%. Glucose levels ranged from 1.7 to 2.9 g/100g, while fructose ranged from 0.9 to 6.9 g/100g, and the crude protein was 11.0 to 16.8%. The acrylamide levels varied significantly (p<0.05) across coffee varieties, with the highest occurring in the Elite D (ED) variety, with 444.8 µg/kg at dark roast. Acrylamide levels also varied significantly (p<0.05) with roasting time. Higher levels of acrylamide occurred in the dark roasted coffee and were lowest in very dark roasted coffee. Acrylamide levels for coffee brewed using the espresso method were 1.7 to 21.9 µg/L. They were highest in Kisansa coffee brewed for 60 s and lowest in the same variety brewed for 10 s. Whereas for the coffee brewed using the French press method, the acrylamide levels were 9.2 to 66.3 µg/L, with the highest (p<0.05) occurring in KR7 brewed for 10 min and the lowest in Kisansa brewed for 3 min. Therefore, the study indicated that there are varietal differences in the physicochemical properties of coffee beans, which in turn influence their acrylamide levels upon roasting and brewing.
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ItemDevelopment and preservation of a starter culture for commercial production of bongo, a traditional fermented milk beverage from Uganda(Makerere University, 2025)Bongo is a popular traditional fermented milk produced spontaneously, or by backslopping. This predisposes the product to microbial contamination, slow fermentation and variations in product sensory properties. Controlled fermentation using defined starter cultures is vital to address these challenges. Three lactic acid bacteria (LAB) previously isolated based on milk acidification and coagulation, Lacticaseibacillus rhamnosus BM55, Lactococcus lactis BM01 and Leuconostoc pseudomesenteroides BM70 were used in this study to evaluate their potential as starter cultures in fermented cows’ milk. The isolates were evaluated both individually and in combination. Microbial counts, pH, titratable acidity, viscosity, flavour development, syneresis and consumer acceptability were determined using standard methods. The sensory profile of Bongo prepared using the cultures, as well as the spontaneously fermented Bongo, was described using Quantitative Descriptive Analysis (QDA). The relationship between the sensory profile and hedonic scores was determined using preference mapping. The most promising combination of isolates (BM01, BM55 and BM70) was lyophilised in 10% (w/v) skimmed milk and 10% (w/v) soluble starch prior to being stored under refrigeration (4 °C) for 6 months. Survival rate and fermentation characteristics (pH, viscosity, titratable acidity and LAB counts) of Bongo made using the starter culture were determined. The combination of all the three isolates showed the highest potential application as a starter culture with the lowest pH, optimal viscosity, minimal syneresis and enhanced flavour development comparable to that of spontaneously produced Bongo. This was further confirmed by the QDA results. Significant correlations were observed between lumpiness, smoothness and astringency underscoring the importance of the choice of microorganism on the product attributes of Bongo. Texture was the major factor responsible for the differences between the Bongo samples produced by the different starter culture isolates. There was a decline in viability and fermentation ability post lyophilisation and storage because the cryoprotectants do not fully prevent cell damage due to freezing effects and dehydration. LAB lyophilised in skimmed milk showed the highest viability (92%) when compared to LAB lyophilised in soluble starch (78%). Bongo made using LAB lyophilised in skimmed milk had a higher viscosity, lower pH, higher titratable acidity compared to that made with LAB lyophilised in soluble starch implying that skimmed milk had a better protective power. The freeze dried culture maintained acidification ability in the first four months of storage at 4 °C. The mixed starter culture containing Lactococcus lactis BM01; Lacticaseibacillus rhamnosus BM55 and Leuconostoc pseudomesenteroides BM70 lyophilised in 10% (w/v) skimmed milk could be adopted for commercial scale processing of Bongo.