STANDARDIZATION OF PROCESS PARAMETERS FOR IDLI BATTER FERMENTATION USING SELECTED STARTER CULTURE COMBINATIONS

Abstract

The present study was carried out to standardize the fermentation of idli batter using selected starter culture combinations, with the aim of achieving consistent fermentation and extending its refrigerated shelf life. To achieve this, five starter cultures, namely Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus plantarum,Lactobacillus fermentum, Lactococcus Iactis, and Saccharomyces cerevisiae, were selected based on their acidification ability, carbon dioxide production, enzymatic activity, and compatibility during mixed-culture fermentation. The selected starter cultures were evaluated in different combinations and inoculum concentrations, and Response Surface Methodology (RSM) using Design-Expert software was employed to optimize the starter culture combination, inoculum concentration, and fermentation time. The resulting idli batters were then evaluated for changes in physico-chemical properties, sensory characteristics, and microbiological quality at fermentation periods of 2, 4 and 6 hours. Based on the responses obtained at different fermentation periods and inoculum concentrations, 6 h was identified as optimum. Among the optimized formulations, LPF at inoculum concentrations of 0.3 mL and LP at 0.2 mL per 100 g batter (LPF 0.3 and LP 0.2 respectively) were selected for further evaluation. The optimized treatments were subsequently subjected to a refrigerated storage study. The fermented batter was packed in 80 μm laminated pouches and stored under refrigerated conditions. Quality evaluation was carried out on the 0th, 7th

, 14th and 21st days of storage. Among the optimized treatments, LPF 0.3 mL/100 g batter showed the most desirable overall response. A gradual decrease in pH along with an increase in titratable acidity was observed, indicating the progress of controlled fermentation. The production of carbon dioxide by the starter cultures contributed to a reduction in bulk density and an increase in volume expansion of the batter, resulting in idlis with a soft, porous, and spongy texture. Compared with the control, the starter culture-treated samples showed better colour stability, controlled acidification, and higher sensory acceptability during storage. Among the different treatments, the optimized LPF consortium, applied as a centrifuged cell suspension at 0.3 ml/100g batter,

retained satisfactory physico-chemical, microbiological and sensory quality for up to 14 days under refrigerated storage. The study indicates that the use of a suitable starter culture combination can help achieve controlled and consistent fermentation of idli batter while improving its quality and refrigerated shelf life.