Microbiological and acidity changes during the traditional production of kirario: An indigenous Kenyan fermented porridge produced from green maize and millet.

摘要

Using a previously pre-tested structured questionnaire, the traditional processing method for kirario (a traditional fermented porridge of the Merus in Kenya) was studied and documented. The biochemical and microbial profile changes during fermentation of kirario , both by the traditional method and in the laboratory were monitored for 48 hours. Samples of kirario from ten localities in the study region were analyzed. Samples of the final products from the traditional method were analyzed for total viable counts (TVC), lactic acid bacteria (LAB), lactococci, yeasts and moulds and coliforms, while the laboratory samples were taken at six (6)-hour intervals and analyzed for TVC, LAB, lactococci, and yeasts and moulds for 48 hours. The traditional product showed average TVC, LAB, lactococci, yeasts and moulds of 9.30, 9.63, 8.62, and 4.83 log10 cfu/ml, respectively. Coliform counts were detected in only two of the samples at <1 log10 cfu/ml. Analysis of the laboratory samples showed similar results. This showed that the production of kirario was reproducible and could be simulated in an industrial set-up for commercialization. In both the laboratory and traditional samples, the microbial counts were monitored at 6 hourly intervals for 48 hours. The initial pH of 6.4 dropped to 3.3 at the end of the fermentation, while the total titratable acidity increased to 3.15% from an initial value of 1.04%. The TVC, LAB, lactococci, yeasts and molds increased from initial counts of 8.20, 8.18, 7.20 and 5.86 log10 cfu/ml to 9.64, 9.55, 5.38 and 0.70 log10 cfu/ml, respectively at the end of the 48-hour fermentation. The coliform counts were low or not detected at all in majority of the samples. These results indicated high degree of hygiene in traditional processing of kirario as indicated by the very low or undetectable coliforms. This was also attributed to the effect of inhibition of growth of coliforms during fermentation. The results were also substantiated by unusually high levels of acid in both the traditional and laboratory products, corresponding to pH 3.0 to 3.5, which indicated high activity of the lactic acid bacteria in kirario .