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.
This study evaluates the antimicrobial activities of a multi-species probiotic ingredient derived from the African opaque sorghum beer during its propagation in a starchy career model. The aim was to establish the optimum growth conditions that warrant the optimum antimicrobial activities in the product. The antimicrobial activities were tested against Gram-positive bacteria (Staphylococcus aureus ATCC 27844, S. aureus MR 825), Gram-negative bacteria (Escherichia coli ATCC 25922, E. coli O157:H7 ATCC 700728, Salmonella typhi R 30951401, Klebsiella pneumoniae ATCC 35657), as well as against yeast (Candida albicans MHMR), using agar disc diffusion method. Also, the growth of viable cells and physicochemical parameters during the propagation were monitored. The results showed that the pH and dry matter content of the probiotic ingredient decrease significantly (p˂0.05) during the propagation whereas the lactic acid, the titratable acidity, lactic acid bacteria (LAB), yeasts and moulds counts increase significantly (p˂0.05). From 0 to 12 h, the product failed to inhibit the growth of all indicator strains. From 24 h and onward, the probiotic career inhibited all indicator strains except for K. pneumoniae (ATCC 35657) which could not be inhibited. Clearly, our study showed that 36 h of the propagation were sufficient to generate a probiotic ingredient with optimum antimicrobial activities.
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