Use of response surface methodology to optimize the drying conditions of a bioactive ingredient derived from the African opaque sorghum beer

Abstract

The present work aims to optimize the heat drying conditions of a bioactive feed ingredient derived from the African opaque sorghum beer. The bioactive ingredient was dried at various temperatures 35 to 50°C and times 5 to 24 h. The effects of the drying conditions on the dry matter, water activity, pH, titratable acidity, bacteriocin, ethanol, lactic acid, yeasts, lactic acid bacteria contents and antimicrobial activity against indicator pathogens (Staphylococcus aureus ATCC 27844, methicillin resistant S. aureus (MRSA), Salmonella typhi R 30951401, Klebsiella pneumoniae ATCC 35657, Escherichia coli ATCC 25922, E. coli O157:H7 ATCC 700728 and Candida albicans MHMR) were studied. Results showed that the temperature was the main factor that affects the bioactivity indicators of the ingredient. The optimal conditions ensuring the best functionality of the ingredient were as follows: Temperature 42°C and drying duration, 24 h. At this optimum condition, water activity (0.49) was low enough to warrant adequate shelf life to the ingredient.