Optimisation of cholesterol reduction in prawn by lactobacillus bulgaricus yoghurt using response surface methodology (RSM) / Norazwa Othman

The purpose of this study was to optimise the cholesterol reduction in prawn by L. bulgaricus yoghurt using Response Surface Methodology (RSM) of MINITAB Software (Version 14). Experimental design was created by RSM whereby test variables; pH of prawn, amount of yoghurt (%), incubation temperature (0C) and incubation time (minutes) were used. Whole part of prawn were blended, changed the pH and mixed thoroughly in different amounts of L. bulgaricus yoghurt and treated differently in terms of incubation temperature and incubation time as suggested by the experimental design of RSM. The optimal centrifugal speed was investigated and relative centrifugal field (RCF) of 1000 x g at the temperature of 2o C for 10 minutes showed the best performance. This speed was able to give 53.57% reduction in total fat content of prawn. This centrifugation condition was used to determine the optimum amount of cholesterol reduced in treated prawn. Cholesterol analysis was carried out according to AOAC Official Method 994.10 and measured using Gas Chromatography: with Flame Ionization Detector (GC-FID). Cholesterol content in prawn was reduced to 75.85% at the optimum condition; pH 6.41 of prawn, 16.3% of L. bulgaricus yoghurt, 36.2 0C of incubation temperature and 30 minutes of incubation time. Verification experiment was also carried out and it was found that there was significantly different at the 5% level between predicted and verified values of cholesterol reduction using the optimum condition determined by RSM. In addition, the significant regression equations or models at the 5% level of confidence interval were also established for the estimation of the percentage reduction of cholesterol in prawn treated by L. bulgaricus yoghurt. This indicates that L. bulgaricus yoghurt is a potential medium to be employed to reduce cholesterol in prawn