Studies on the safety of Obushera and probiotic potential of selected lactic acid bacteria

A thesis submitted to Makerere University College of Agricultural and Environmental Sciences in partial fulfillment of the requirements for the award of Doctorate of Philosophy in Food Science and Technology.

The rising demand for Obushera, a traditional fermented sorghum/millet beverage originally from south western Uganda, is increasing its commercialization in cities such as Kampala. Haphazard production is currently a trend owing to the lax enforcement of food safety regulations thus threatening consumer safety. This study examined bacterial and total aflatoxin contamination of Obushera in Kampala. The criteria and methods for probiotics screening were also reviewed. Consequently, the probiotic potentials of Obushera starters: Lactobacillus plantarum MNC 21, Lactococcus lactis MNC 24 and Weisella confusa MNC 20 with regard to improving the beverage‟s safety were examined. Lactobacillus rhamnosus yoba 2012, a known probiotic was the reference. Obushera (n=59), sorghum flour (n=20) and millet flour (n=20) were analyzed for E. coli, total and thermo-tolerant coliforms, staphylococci, Salmonella spp., molds and total aflatoxins. Data on processors‟ food safety knowledge, attitudes and practices (KAP) were collected using researcher administered questionnaires. Obushera had 0.0 – 7.3 log cfu/mL total and thermo-tolerant coliforms, 0.0 – 6.2 log cfu/mL E. coli, 0.0 – 8.1 log cfu/mL staphylococci, 2.0 – 5.5 log cfu/mL molds and 10.4 ± 6.1 ppb total aflatoxins. Flours had 3.2 – 7.3 log cfu/g total and thermo-tolerant coliforms, 1.0 – 4.9 log cfu/g E. coli, 2.4 – 7.3 log cfu/g staphylococci, 0.0 – 6.5 log cfu/g molds and 9.9 – 22.3 pp total aflatoxins. Salmonella spp. was undetected. Obushera samples (95%) had coliforms and staphylococci above the safety limits. Processors had fairly good knowledge (63.0% ± 2.3) and attitudes (52.2% ± 3.0) but fairly poor practices (38.7% ± 2.4). There was no association between the KAP and Obushera safety. Probiotics screening entails evaluation of isolates for tolerance to gastric conditions, safety and probiotic benefit. The starters tolerated pH=3, 1% bile and had Bile Salt Hydrolase activity. MNC 20 and MNC 21 produced agmatine. The three starters were: non mucolytic, resistant to 10 of the 21 antibiotics tested, slightly hydrophobic, autoagrgregative, co-aggregative and had ileal binding abilities. They were antagonistic against virulent, acid tolerant and antibiotic resistant E. coli isolated from Obushera. They bound 19.3 – 69.4% aflatoxin B1 in a solution spiked with 1000 ppb of the toxin. Binding efficiency was: yoba 2012 = MNC 21 > MNC 20 = MNC 24. Therefore, the starters could be used to improve Obushera safety whilst also improving health.

Mr. Samuel K. Byakika Food Technology and Business Incubation Center (FTBIC)