Screening local cereal-based beverages in Tanzania for yeast contaminants

This research article published by International Journal of Biosciences, Vol. 18, No. 2, 2021During spontaneous fermentation of cereals; yeasts ferment carbohydrates to produce alcohol and they also provide vitamins, amino acids, peptides, and nucleotides needed by lactic acid bacteria as well as produce flavour compounds. Nevertheless, spontaneous fermentation is prone to yeast contamination from the surroundings which pose a health risk of opportunistic yeast infection. A study was carried out involving culturing, isolation and identification of yeast contaminants present in the local cereal-based beverages namely Kindi, Kimpumu, Togwa and Mbege purposively sampled and collected from Morogoro, Mbeya and Kilimanjaro regions in Tanzania between February and May 2019. The results disclosed 24% of the yeasts actively involved in the fermentation were opportunistic and identified as Candida zeylanoides, Candida albicans, Cryptococcus gattii, Rhodotorula minuta, Candida ciferrii, and Candida dubliniensis. Such contamination levels from the studied samples sets a base for further research to establish mechanisms of reducing exposure of cereal-based beverage consumers to pathogenic effects of the opportunistic yeasts which may include infections by Candida spp

Optimisation of fermentation processes of local cereal-based beverages to produce improved cereal based probiotic beverages.

A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Life Sciences of the Nelson Mandela African Institution of Science and TechnologyFermented cereal-based probiotic beverages are rare and have rarely been produced in Tanzania. Though the beverages are novel, the potentiality of such beverages has for some decades been exhibited through local fermented cereal-based beverages. In recent years there has been a paradigm shift towards non-diary probiotic products because of the negative health effects milk and dairy products have on the multitude of people around the world. A quantitative study employing purposeful sampling was carried out in three regions of Mbeya, Morogoro and Kilimanjaro whereby in each of the regions; quadruplicate samples of either of the traditional cereal-based beverages locally known as Kindi, Kimpumu, Togwa or Mbege were collected from a target village and stored at 4 °C in the laboratory. Identification of probiotic microbes in the local beverages was done and probiotic Kindi, Kimpumu, Mbege and Togwa were developed using pure cultures of the identified probiotic bacteria. Probiotic cultures used were Lactobacillus brevis for Togwa, Lactobacillus plantarum for Kimpumu and Mbege and Pediococcus pentosaceus for Kindi. After 24-48 h of controlled fermentation at 37 °C; results showed that the prepared cereal-based beverages were probiotic with mean viable cell counts of 1 x 1011 cfu/mL and mean pH 4.77. During storage the probiotic cereal beverages remained stable for five days at 25 °C and 28 days (4 weeks) at 4 °C with viable cell count of 2.0 x 1011 cfu/mL and pH 3.83 at 25 °C and viable cell count of 2.0 x 1011 cfu/mL and pH 4.08 at 4 °C, respectively. There was no growth of pathogens in the beverages. The four cereal based probiotic beverages were equally accepted by consumers through a sensorial evaluation. This study shows that controlled fermentation of cereals using carefully selected probiotic bacteria results in probiotic cereal based-beverages with good quality attributes and safety and further advance the knowledge on fermented cereal substrates as nutrient-rich and promising delivery vehicles for probiotics by sustaining the growth of a large population of lactic acid bacteria