STARTERCULTURE DEVELOPMENT AND FERMENTATION OF OROCHROMISNILOTICIS (NILETILAPIA) PREPARED WITH DIFFERENT MARINATING AGENTS

Abstract

ABSTRACT Fermentation of fish is meant to extend the shelf life of fish, improve sensory characteristics and enable consumers to access benefiting microorganisms. Dried fermented fishier stapling many cuisines, particular in coastal areas. However, discrepancies in fermentation methods and sensory quality have as substantial impaction consumer's acceptability and food safety. This research aimed to screen for possible isolates that could be used as starter cultures during spontaneous fermentation of Oreochromis niloticus identify the best isolates using morphological, biochemicalandmoleculartechniques,fermentwiththeselectedisolatesandtodetermine sensory acceptability of dried fermented fish. Marinated fish were spontaneously fermented at 10‘Cfor12daystoisolatestarterculturesanddeterminebestfermentationperiod.Coloniesof bacteria isolated with MRS (de Man Rogosa and Sharpe agar) plates during spontaneous fermentation of Oreochromisniloticus were characterized, identified and used as starter cultures. Fermentedfishwereovendriedat60’Cfor 12hours. Proximate analysis of dried fermented fish was done using standard methods. The appearance, aroma, taste, tactile texture, overall acceptabilityoffermentedfishwereevaluated.Datawereanalyzedusingone-wayanalysisof variance, followed by Duncan's multiple range test, Pñ0.05 was considered significant. Results of fermentationperiodonphysicochemicalparametersrevealed10daysfermentationperiodat10 ‘*was the best as protein content increased from initial 23.05 to 29.03 in com base fermented fish and23.86to30.83incassavabasefermentedfish.Suspectedcontaminatingorganismswere completely inhibited bytheactivitiesofthestartercultures;thesystembecameslightlyacidic with Total bacteria count (TBC)7.8^109/cfu and Lactic acid bacteria (LAB) 3.1•10'/cfu for com base while for cassava base, TBC-1.2•109/cfu and LAB-2.2•105/cfu for cassava base. Comparativeproximateanalysisoffreshfish,fermentedfishanddriedfermentedfish showed

protein content of(24.12, 31.92, 30.04 %), Fat content of(2.69, 2.16, 1.88 %), and Ash content of (5.82,7.23,9.12%), respectively. The main and interactive effect so base and isolate Sensory acceptability showed that carbohydrate bases had no significant (P>0.05)effect on fermented fish acceptability. Starter cultures had significant effect on taste (P= 0.004) and aroma (P=0.009).Combinedeffectofcarbohydratebaseandstartercultureshadsignificanteffecton appearance(P=0.002)and aroma(P= 0.004). Sensory attributes revealed that the effects of the three starter cultures on the fermented fish were not significantly different (P>0.05). The selected bacteriaisolateswereidentifiedasLactobacilluspentosusstrain,Streptococcusthermophilusstrain1,and Streptococcus thermophilus strain2,respectively. Dried fermented fish had improved values compared with fresh fish in Na (62.80+3.4vs.52.50z2.3),and Fe (41.90+6.7) mg/100g. This study demonstrates the potential of these developed stains as starter cultures to improve the quality and nutritional value of fermented Oreochromis niloticus.