The Predominant Lactic Acid Microorganisms of Spontaneously Fermented Amala, a Yam Food Product

Aim: Using Four (4) varieties of yam (Dioscorea rotundata), namely, TDr Pepa, TDr Amila, TDr Alumaco and TDr 95/19177 differences in the types of organisms responsible for spontaneous fermentation were evaluated. The organoleptic properties of the final food products were also subjected to testing, in order to determine if these properties were reproducible.

Study Design: Using a Complete Randomized Design (CRD) with three replications, the four varieties of yam were tested for significant differences in the characteristics of interest among the final products.

Place and Duration of Study: The present study was conducted between March and May 2016 at Ede. The yam tubers were sourced from the International Institute for Tropical Agriculture (IITA), Ibadan.

Methodology: In a standardised spontaneous fermentation set-up, four varieties of yam, were sampled eight hourly over a period of 24 hours, for lactic acid microorganisms. Representative microbial populations that were incubated anaerobically were isolated, counted, identified and characterised using standard microbiological protocols. The final products were evaluated for their organoleptic properties.

Results: The only isolated predominant lactic acid bacterial organisms was Lactobacillus brevis, while, Rhizopus spp, Aspergillus niger, Aspergillus flavus and Neurospora spp were identified as the representative lactic acid fungal isolates. The results revealed slight differences between the final products (amala samples) that were earlier processed using sun or oven-drying, although the differences were not statistically significant at p= .05 using ANOVA (one-way analysis of variance).

Conclusion: The present results confirmed that the prevailing microenvironment is the prime determinant of the predominant organisms in the fermentation process and consequently in the sensory properties of the final product. The present spontaneous fermentation data indicate that similar lactic acid organisms were isolated from the different yam varieties in the fermentation set up. The foregoing shows that the organoleptic characteristics specific to this test location may be reproduced using the isolated lactic acid microorganisms, perhaps on an industrial scale.