Development Of Starter Culture For Kocho A Traditional Fermented Food Of Ethiopia

Enset fermentation for the production of kocho vary depending on the locality of Ethiopia. In rnthis study, 16 kocho samples originating from four different areas were investigated. They rnvaried both in the fermentation technique and the duration of fermentation. Microbial rncommunities of samples were analysed using culture-independent 16S amplicon high-rnthroughput sequencing. In addition, bacterial strains were isolated and identified using rnphenotypic and genotypic characteristics. Furthermore, the volatile profiles were rncharacterised by HS-SPME treatment coupled with GC/MS to investigate the correlation of rnthe diversity of the microbiota and volatile profiles. In ordered to select the potential starter rnculture, the dominant Lactobacillus strains were selected and investigate its growth potential. rnAccording to the results of culture-dependent methods LAB and aerobic, mesophilic bacteria rnconstituted the dominant microorganisms. A total of 137 strains were isolated and identified rnin both phenotypic and genotypic characteristics. Lactobacillus plantarum and Lactobacillus rnbrevis were found abundantly. Lactobacillus paracasei, Lactobacillus fermentum rnLactobacillus paracollinoides, Acetobacter pasteurianus and Acetobacter rnpersici/farinalis/malorum were also identified. A total of 18 phyla was identified from kocho rnsamples using culture-independent method. Firmicutes and Proteobacteria phyla were found rnabundantly (> 90%). Next, to those phyla, Bacteroidetes and Actinobacteria were the rndominant ones and the rest were found below 0.01%. Lactobacillus and Acetobacter were the rnmost dominant genera. Clostridium, rnBifidobacterium, Enterobacteriaceae, rnCaproiciproducens and Prevotella were also identified with a relative abundance in some samples. The microbiota of samples from Dilla was mostly (ca. 70% to 80%) dominated by rnAcetobacter. Wolkite samples was dominated by Lactobacillus, which occurred in all rnsamples in varying abundances. rnrnIn total, 33 volatile organic compounds were identified from kocho samples. Acetic acid and rnbutanoic acid prevailed in all samples. This could be due to the abundance of Clostridium and rnacetic acid bacteria. Further, relatively high concentrations of hexanoic acid (caproic acid) rnwere detected in the longer fermented Wolkite samples and especially the samples W6 and rnW7. This could be due to the presence of Caproiciproducens species in those samples. rnDifferent enset processing practices and fermentation period caused a quantitative difference rnin the volatile profiles of samples. The existence of a high amount of free fatty acid, rnparticularly butanoic acid, acetic acid, and pentatonic acid might give kocho a strong odor. rnMost L. plantarum showed rapid acidification and the higher growth rate than L. brevis. rnThere were significant differences (P≤ 0.05) in pH reduction between L. plantarum and L. rnbrevis. Based on these results L. plantarum (n=10) and L. brevis (n=3) were selected as rnpossible starter strains and applied to enset pulp in laboratory scale. These starter strains rnshowed fast pH reduction, increased microbial load than the control sample and the rnpossibility of a single strain in the fermentation of enset pulps for the production of kocho. rnOptimization of enset fermentation using RSM revealed that time, amount of starter culture rnand types of starter strain affected the sensory attributes of kocho. The pH values were rnsignificantly different for the different formulation of kocho products (P ≤ 0.05). The overall rnacceptability of kocho prepared in the farmer backyard and in laboratory scales was not rnsignificantly different (P ≥ 0.05). The preferred sensory quality of kocho was produced using rn2% L. plantarum starter strain in 6 days of fermentation time.Kocho samples prepared in different areas and by different processing methods varied both in rnthe composition of the microbiota and in the quantity of volatile profiles. L. plantarum and L. rnbrevis were found to be the most abundent LAB species and could be detected in all samples rnfrom the beginning to the later stages of kocho fermetation. The volatile compounds which rnlead to the characteristic flavor and odor of kocho could be identified as short-chain fatty rnacids which were presumably produced by the microbial activity. The abundance Firmicutes rnand Proteobacteria phylum could be the main reason for the detection of a high amount of rnshort-chain fatty acids. Therefore, correlation of microbiota composition and volatile profile rnof kocho contributes to improving the knowledge of the fermentation process. Moreover, this rninformation also used in the selection and development of starter culture. L. plantarum and L. rnbrevis are the potential starter culture in the production of kocho. Application of starter rnculture for the production of kocho improve fermentation time and overall consumer rnacceptability of the product.

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