Storage behaviour and functionality of a heat stabilized starter derived from an African opaque sorghum beer

Abstract

Tchoukoutou is a traditional sorghum opaque beer produced and consumed in Benin. It is obtained from an uncontrolled fermentation of sorghum wort using a traditional starter called "kpete-kpete". The present study assessed the effects of storage duration on the physicochemical and microbiological characteristics as well as on the functional properties of the heat stabilized starter produced from "kpete-kpete". The physicochemical characteristics of the stabilized starter were not significantly affected by the storage duration. After 60.0 days of storage, the dry matter, pH and titratable acidity were stable with mean values of 92.5%, 4.76 and 1.33 g/kg, respectively. However, the microbial characteristics of the product were significantly affected by the storage duration. Yeasts, lactic acid bacteria (LAB) and total mesophilic aerobic counts were modified following three phases: a latency phase (between 0 and 10 days), an exponential growth phase (between 10 and 40 days) and the decline phase (between 40 and 60 days). As compared to the stabilized starter, the physicochemical characteristics of "kpete-kpete'' were extensively modified after 15 days of storage. In the traditional "kpete-kpete'', all the major groups of microorganisms, reached their maximum growth phase after 10 days of storage suggesting that they would have lost their fermentation power afterwards. The fermentation test performed using stabilized starter sampled at different growth phases, revealed that the starter of 25 days of storage possesses better fermentation capacity. In these conditions, the fermentation duration was reduced to 16 instead of 24 h.