In this study, the microbiological quality of traditionally fermented milk from Northern Uganda and Western Kenya was analysed. Six samples of typical traditionally fermented milk were collected randomly from traditional cattle keepers in Karamojong (UG 1) and Acholi (UG 2) in Northern Uganda and Kalenjin in Western Kenya (KE). The microbial quality of the collected samples was assessed through the use of conventional methods for total aerobic mesophilic bacteria, total coliform, lactic acid bacteria, Staphylococcus aureus, Listeria monocytogenes, yeasts, and mould counts. The mean aerobic mesophilic bacterial counts were 5.14 × 10⁹ coliform forming units (cfu)/mL. The mean counts for mesophilic lactobacilli ranged from 10⁶ to 10⁸ cfu/mL. The mean thermophilic lactobacilli count ranged from 10⁷ to 10⁹ cfu/mL, while the mean thermophilic lactococci counts ranged from 10⁶ to 10⁹ cfu/mL. On the other hand, the Streptococci counts were between 10⁶ and 10⁸ cfu/mL. The mean count for the non-sorbitol E. coli was 3.87 × 10³ cfu/mL. These results suggest that although the pH of the traditional yoghurt in this study was low, the acidity was not sufficient to inhibit growth of microorganisms in the product. Although it is difficult to avoid the microbial contamination of milk during milking, it is of the utmost importance to maintain a very high level of hygiene in dairy farming practices, and the correct cleaning of teats during milking is very important for good udder health and optimum milk quality, and to ensure safety. The results regarding microbial contamination pose public health concerns, and therefore the appropriate government agencies must pay attention to ensure that the environment in which yoghurt is produced is in the best condition to reduce contamination.

The antimicrobial activity of the essential oils of black pepper (BPE) and cinnamon bark (CE) extracts against E. fergusonii was assessed in pasteurized full cream milk during and post-fermentation. The milk was fermented with 1% (v/v) of Lactobacillus delbrueckii subspecies bulgaricus (NCIMB 11778) and Streptococcus thermophilus (NCIMB 10387) (approx. 10⁶ cfu/mL each) and incubated and stored at 25 °C for 5 days (144 h) or at 43 °C for 24 h and then stored at 25 °C for 120 h. The milk was spiked with E. fergusonii at the start of fermentation by the lactic acid bacteria (pre-fermentation contamination) for after fermentation (post fermentation contamination). BPE and CE were applied at concentrations based on their minimum inhibitory concentration of 0.5% and 0.25% respectively as follows: 0.5% BPE alone; 0.125% BPE with 0.1875% CE; 0.25% BPE with 0.125% CE; 0.375% BPE with 0.0625% CE; 0.25% CE alone. Results showed that during fermentation at 25 °C, E. fergusonii grew to a similar level (approx. 10⁹ CFU/mL) in control samples and 10⁸ CFU/mL when BPE or CE were added alone. Whereas, in the samples with the combined essential oils, the bacterium grew to 10⁶–10⁷ CFU/mL only. During the milk fermentation at 43 °C, E. fergusonii grew to approx. 10⁹ CFU/mL in samples without treatment. However, it was not detected in samples containing mixed BPE with CE after 8, 10 and 12 h of fermentation. Subsequent storage at 25 °C resulted in undetectable levels of the bacterium in all the samples treated with BPE or CE after 24 h of storage. These results indicated that BPE in combination with CE reduced growth during fermentation and was bactericidal during storage.

The antimicrobial activities of extracts of clove buds (CL) and cinnamon bark (CE) were investigated individually and in combination in fermenting and fermented full cream milk against Escherichia fergusonii and Salmonella typhimurium. Clove and cinnamon were extracted for their essential oils (EOs) and eugenol and cinnamaldehyde were the major components representing 60-80% of the total oils. Preheated milk was inoculated with 1% (v/v) of a mixed culture of Lactobacillus delbrueckii subspecies bulgaricus (NCIMB 11778) and Streptococcus thermophilus (NCIMB 10387) and incubated at 25 or 37oC for 24 h. E. fergusonii or S. typhimurium (3 x 105 CFU/mL) were introduced into the milk pre - or post-fermentation. CL and CE were added at the same time as the pathogens based on their Minimum Inhibitory Concentrations of 0.25% for both pathogens as follows: CL and CE at 0.25% each alone; 0.0625% CL/0.1875% CE; 0.125% CL/ 0.125% CE; and 0.1875% CL/0.0625% CE. When added at the start of fermentation at 25oC, the CL and CE combinations inhibited the growth of E. fergusonii, and S. typhimurium, whereas at 37oC and associated with more rapid and higher acidification, the CL and CE combinations showed a marked antimicrobial activity against both pathogens. In post fermentation inoculated milk, survival of E. fergusonii and S. typhimurium was reduced by all CL and/ or CE treatments and were undetectable in samples containing 0.0625% CE with 0.1875% CL and 0.1875% CE with 0.0625% CL within 48 to 72 h of storage. The extent of the effect was most marked in the samples fermented at 37oC compared to 25oC and related to the pH after fermentation of 4.2 ±0.2 and 5.0 ±0.2 respectively. The use of these extracts both during fermentation and storage have the potential to enhance the microbiological safety of these products.

In this study, the microbiological quality of traditionally made yoghurt from Northern Uganda and Western Kenya were analysed. Six samples of typical traditionally fermented milk were randomly collected from traditional cattle keepers from Karamojong (UG 1) and Acholi (UG 2) in Northern Uganda), and Kalenjin in Western Kenya (KE). Analysis was carried out for microbial quality of the collected samples and was assessed using the conventional methods for total aerobic mesophilic bacteria, total coliform, lactic acid bacteria, Staphylococcus aureus, Listeria monocytogenes, yeasts, and mould counts. The results showed that the pH of the samples was low (2.9- 3.6). The mean aerobic mesophilic bacterial counts were 5.14 x 109 cfu/ml. The mean counts for mesophilic lactobacilli ranged from x 106 to x 108, cfu/ml. The mean thermophilic lactobacilli count ranged from x 107, to x 109, cfu/ml. However, the thermophilic lactococci counts ranged from x 106, to x 109, cfu/ml. On the other hand, the Streptococci counts were between x 106 to x 108 cfu/ml. The mean counts for the non-Sorbitol E. coli was 3.87 x 103 cfu/ml. The results suggest that although the pH of the yoghurt made in the Acholi and Karamojong (Northern Uganda) and in Kalenjin (Kenya) areas was low, the level of bacteria, yeast, and mould counts indicated poor microbiological quality control. This poses public health concerns. Therefore, attention of the appropriate government agencies is needed to ensure that environment of yogurt produced in a traditional setting in most appropriate condition to reduce contamination.