Inactivation of bacterial pathogens in yoba mutandabota, a dairy product fermented with the probiotic Lactobacillus rhamnosus yoba

• Published in: International journal of food microbiology Vol. 217; pp. 42 - 48
• Main Authors: Mpofu, Augustine, Linnemann, Anita R., Nout, Martinus J.R., Zwietering, Marcel H., Smid, Eddy J., den Besten, Heidy M.W.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 18.01.2016
• Subjects: Animals; Bacillus cereus - growth & development; Baobab fruit; Bioreactors; Campylobacter jejuni - growth & development; Cattle; Challenge test; Dairy Products - microbiology; Escherichia coli O157 - growth & development; Female; Fermentation; Food Microbiology; Food Microbiology Laboratory; Food Quality and Design; Food-borne infection; Humans; Laboratorium Levensmiddelenmicrobiologie; Lactobacillus rhamnosus - metabolism; Levensmiddelenmicrobiologie; LGG; Listeria monocytogenes - growth & development; Probiotics - pharmacology; Salmonella - growth & development; Survival; VLAG; Food-borne infection; Fermentation; Challenge test; Survival; LGG; Baobab fruit
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2015.09.016

Mutandabota is a dairy product consumed as a major source of proteins and micronutrients in Southern Africa. In this study the microbial safety of traditional and a variant of mutandabota fermented with the probiotic Lactobacillus rhamnosus yoba (yoba mutandabota) was investigated by challenging the products with five important food pathogens: Listeria monocytogenes, Salmonella spp., Campylobacter jejuni, Escherichia coli O157:H7 and Bacillus cereus. Pasteurized full-fat cow's milk was used for producing traditional and yoba mutandabota, and was inoculated with a cocktail of strains of the pathogens at an inoculum level of 5.5logcfu/mL. Survival of the pathogens was monitored over a potential consumption time of 24h for traditional mutandabota, and over 24h of fermentation followed by 24h of potential consumption time for yoba mutandabota. In traditional mutandabota (pH3.4±0.1) no viable cells of B. cereus and C. jejuni were detected 3h after inoculation, while L. monocytogenes, E. coli O157:H7 and Salmonella spp. significantly declined (P<0.05), but could still be detected (<3.5log inactivation) at the end of the potential consumption time. This indicated that consumption of traditional mutandabota exposes consumers to the risk of food-borne microbial infections. In yoba mutandabota, L. rhamnosus yoba grew from 5.5±0.1logcfu/mL to 9.1±0.4logcfu/mL in the presence of pathogens. The pH of yoba mutandabota dropped from 4.2±0.1 to 3.3±0.1 after 24h of fermentation, mainly due to organic acids produced during fermentation. Only Salmonella spp. was able to grow in yoba mutandabota during the first 9h of fermentation, but then decreased in viable plate count. None of the tested pathogens were detected (>3.5log inactivation) after 3h into potential consumption time of yoba mutandabota. Inactivation of pathogens in mutandabota is of public health significance because food-borne pathogens endanger public health upon consumption of contaminated food, especially in Southern Africa where there are many vulnerable consumers of mutandabota such as children, elderly and immuno-compromised people with HIV/AIDS. The findings of this study demonstrate that mutandabota fermented with L. rhamnosus yoba has antimicrobial properties against the tested pathogens and it is safer compared to the traditional mutandabota. •L. monocytogenes, E. coli and Salmonella spp. survived in traditional mutandabota.•None of the tested bacterial pathogens survived in probiotic mutandabota.•Fermenting mutandabota with L. rhamnosus yoba enhances its microbiological safety.•L. rhamnosus yoba grew to 9logcfu/mL in mutandabota inoculated with pathogens.•Probiotic mutandabota is safer stored than traditional mutandabota.