Fermentation optimization for a probiotic local northeastern Indian rice beer and application to local cassava and plantain beer production

Response surface methodology was employed to determine the optimal conditions of time and temperature for the fermentation of a local North East Indian rice beer. The same conditions were then applied to prepare local beers from cassava ( Manihot esculanta ) and plantain ( Musa ABB). Saccharomyces cerevisiae , Aspergillus oryzae and Lactobacillus plantarum were used to carry out the fermentation process. Thirteen experimental runs, based on a two‐factor five‐level design were carried out according to a central composite rotatable design. The independent variables were fermentation time (24–216 h) and temperature (25–40°C). The responses studied were content of protein, alcohol, total polyphenols, reducing sugars as well as titratable acidity and L . plantarum count. Numerical optimization predicted that a fermentation period of 143 h at a temperature of 33°C would result in a desirable rice beer, with response values of protein content OF 0.77%, alcohol content OF 6.99%, L . plantarum count of 7.08 log CFU mL −1 , polyphenol content of 34.46 mg/100 g, reducing sugars of 2.39% and a titratable acidity of 0.34%. Cassava and plantain beers were prepared using the optimized parameters of the rice beer experiments and the resultant beers exhibited the desired chemical parameters, suggesting applicability of the conditions to preparing these types of local beers from a wider range of substrates. Copyright © 2015 The Institute of Brewing & Distilling