Abstract

The microorganisms and compounds influencing the organoleptic properties of Ugba were studied. Ugba was produced by the fermentation of boiled and shredded seeds of African oil bean. The pure cultures of microorganisms responsible for Ugba fermentation were isolated from Ugba samples, produced by traditional method and were used in singles and in combination to ferment African oil bean shreds. The Ugba so fermented were analyzed organoleptically and sensory scores statistically analyzed using analysis of variance at P<0.5. Compounds in the samples of oil extracted from unfermented African oil bean shreds and Ugba samples fermented for 72 h with the microorganisms (in singles and in combinations) were analyzed by gas chromatograph. The result showed that the following microorganisms were involved in the fermentation of Ugba:Staphylococcus saprophyticus, Bacillus pumilus, Bacillus subtilis and Bacillus licheniformis. The organoleptic tests showed that in all parameters tested, the sample fermented by mixed starter culture of B. subtilis and B. licheniformis was generally liked, which implied ‘overall best’. Compounds found in unfermented Ugba were nineteen in number. Out of this number, eleven were found in unfermented samples, while eight were in the fermented Ugba. The best sample contained the following compounds: ethanol, ethyl stearate, ethyl oleate, ethyl linoteate, ethyl phenol and ethyl octanoate (their percentage concentration ranged from 2.69% for ethyl octanoate to 67.85% for ethanol). These compounds influenced the perceived Ugba flavor but had no direct influence on color and texture of Ugba sample.

Key words: African oil bean seed, Ugba, fermentation, microorganisms, starter culture, organoleptic characteristics, flavor compounds.