Identification, Isolation and Characterization of Suitable Lactic Acid Bacterial Strain for Minimizing Fermentation Time of Kocho
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Date
2017-10
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Addis Ababa University
Abstract
Kocho is a traditional food prepared through fermentation of decorticated Enset in Southern Ethiopia. It has been produced for many years and is being consumed in the region. Various research findings were reported on Enset with major concerns such as food safety and security issues, microbial dynamics of enset fermentation, microbial spoilage and accompanying changes, biochemical changes during fermentation and the effect of altitude on microbial successions. However, gaps were observed during Kocho fermentation, involving lactic acid bacterial (LAB) strain for traditional Kocho fermentation, standardization and optimization of the process. Kocho fermentation has been done in underground pit for a minimum of four months. This long time of fermentation has become a problem of food insecurity, and its minimization is the main concern of this thesis research. Three Kocho samples (Month-1, Months-3 and Months-6) and three Enset trial varieties (Agade, Disho and Gimbo) were taken from Morsito Wereda of SNNP, Ethiopia. The temperature and pH of fermented mass samples (Month-1, Months-3 and Months-6) were measured and recorded as 32, 27 and 290C and 4.78, 4.47 and 4.39, respectively. From each of the three samples, 1mg was taken and serial dilution was prepared, thereafter 0.1ml from each serial dilution factor was inoculated to 54 petri plates and incubated at 25, 30 and 350C temperatures. Growth of mesophilic microbes was recorded from each plate. The results showed that colony forming units of microbes were the highest in Month-1 sample at the temperature of 300C. Based on morphological structure, color and size, LAB were identified, isolated, re-cultured and purified to single strain. White, small and round structure of the strain were stored at 40C. By using Enset trial variety samples as a source of carbon, broth media were prepared according to MRS composition. 30-35 CFU of the pure strain was inoculated to each broth medium, and lactic acid concentration was determined by pH meter for 36 days with 4 days interval at 35 and 300C incubation temperatures. Generally, pH dropped down linearly for both temperatures and for the three Enset trial variety samples up to 23rd day of fermentation and became constant (~pH=4.50) at 24-28th day and reached ~pH=5.30 at 36th day for all varieties. However, pH decreased faster at 350C for all Enset trial varieties, and Disho fermentation dropped faster for eight days than others, and long-delayed from 8-16th day. The pH and temperature of the experiment corresponded with pH and temperature that were recorded during sample collection of sample Month-6. The result showed that only 24-28 days are needed to get Kocho with good texture, fl
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Keywords
Decortication, Enset, Fermentation, Kocho Lactic Acid Bacteria