DEVELOPMENT OF STARTER CULTURE FROM LACTIC ACID BACTERIA AND YEAST ISOLATED FROM INJERA SOURDOUGH

Abstract

In Ethiopia, Injera is a national staple food that is consumed daily in almost every household. It is prepared through spontaneous fermentation with the involvements of different microbial groups. However, the quality is not consistent from place to place and even from households to households. So, this study was aimed to develop starter culture from Lactic acid bacteria (LAB) and yeast from injera sourdough with the view of improving Injera preparation. In this study, a total of 40 sourdough samples were collected from households, microenterprises, and hotels from Addis Ababa, Adama, Debre Birhan, Bahir Dar and Gondar. Both LAB and yeast isolates were isolated from all samples. The selected isolates were characterize using morphological biochemical and molecular methods. The data was analyzed using SPSS and R software. From a total of 50 LAB and 50 yeast isolated, 10 LAB and 12 yeast isolates were selected based on glucose fermentation performance of high acid and gas production for further screening to develop starter culture. All the LAB isolates were white in color and small shaped colonies were observed on MRS agar medium after incubating at 37oC for 48 hours. All the isolates were also gram positive and showed negative for catalase and KOH, and positive for acid production. Out of twelve yeast isolates, nine of them were white and circular shaped while the rest three were gray and irregular shaped colonies as observed on YPD agar medium after incubating at 30oC for 72 hours. All yeast isolates were fermented glucose, sucrose, maltose, and mannose and ten isolates had fermented galactose. On the other hand, all the isolates were negative for lactose, cellobiose, xylose, and inulin. The growth of isolated yeast and LAB at different temperature and pH levels indicated that all isolated cultures grew best at 37oC and 30oC and 5.5 pH respectively. Out of 10 LAB and 12 yeast isolates were selected for starter culture development based on their acid and gas production potentials, growth performance and dough raising capacity, and hydrogen sulfide screening and acidification power for yeast and LAB respectively, 5 yeast and 4 LAB isolates had a high potential to develop starter culture. Combination of starter cultures of LAB (AD1) and yeast (BD2), two yeast and one LAB isolate (DB2+GO1+BD9), Irsho (back slopping), yeast (GO3+GO9) and LAB (BD6+GO7) were used to ferment Injera dough within 48 hours. A sensory attribute of Injera made from developed starter culture and irsho showed significant difference in flavor, aroma, texture, color and overall acceptability. Among the isolates, combination of LAB (AD1) and yeast (BD2) starters were the most acceptable (score of 8.88=like extremely) isolates for preparing Injera. Therefore, the LAB isolate (AD1) and yeast isolate (BD2), starter combination can be used for production of acceptable Injera.