Improvement of indigenous starter cultures

Abstract

The production of fermented foods is based on the use of starter cultures. Recently, new starter cultures with an industrially important functionality are being developed. The starter culture can contribute to the microbial safety or offer one or more organoleptic, technological, nutritional, or health advantages. Examples are starter cultures that produce antimicrobial substances, sugar polymers, sweeteners, aromatic compounds, vitamins, or useful enzymes, or that have probiotic properties. Surveys were conducted in order to collect wild flora found in African cereal based products (Akpan, Gowé, Kenkey, Kishk Sa’eedi) from different rural areas in Benin, Ghana and Egypt. In such places the fermentation process of these products occurs naturally with no addition of industrial starter cultures. Samples during processing were collected and lactic acid bacteria or related cultures were isolated. Out of 280 isolates of lactic acid bacteria from Laban Zeeir and kishk Sa’eedi samples. The isolates were pre identified as 199 Lactobacillus, 71 Enterococcus, 4 Streptococcus and 6 lactococcus. 151 isolates, which were able to grow in milk at different temperatures with the absence of off-flavors, were identified using phenotypic methods and the rep-PCR technique. Lactobacillus (104 strains) were dominant, followed by genus Enterococcus spp (37 strains, and the genus Lactococcus (5 strains). Only two of Streptococci, two Leuconostoc and one Pediococci were also isolated and identified from Laban Zeeir. The strains were tested for efficiency of biomass production and separation, acidifying activity, autolytic and aminopeptidase properties, antagonistic activities and slime production. Strains of Lact. lactis ssp lactis, E. faecium, Lb. fermentum and Lb. delbrueckii ssp lactis which showed outstanding performances and are currently investigated in re-engineering Kishk Sa’eedi trials. In the work of selection culture from Akpan, a total of 88 isolates from MRS were purified and kept at - 80°C in MRS broth containing 30% (v/v) sterilized for further identification. From YEA, a total of 65 yeast isolates were purified and kept in Sabouraud Liquid Medium containing 30% of sterilized glycerol at -80°C. Grouping of these strains is planned for future steps. The identification of isolated from Akpan and Gowe is requested 6 months. Lactic acid bacteria and yeast isolates from kenkey were selected for potential as starter culture based on investigation of their technological properties including Rate of acidification of steeped dehulled maize grains and dehulled maize dough, amylase secretion and antimicrobial activity towards enteric pathogens. Ten trails of Kenkey were made using dough fermented by different selected cultures. The trials were, 1:control fermentation (without starter culture),2: L.brevis, 3: L.fermentum, 4: S. cerevisiea+C. krusei, 5: L.fermentum + S. cerevisiae; 6: L.fermentum+C. krusei,7:L.brevis + C. krusei, 8: L.fermentum+S. cerevisiae + C. krusei, 9:L.fermentum+L.brevis+ C. krusei; 10: L.fermentum+L.brevis+C. krusei + S. cerevisiae. Trial 9 received the highest score of overall acceptability