Optimization of Whey-Based or Nonfat Dry Milk-Based Media for Production of pH Controlled Bulk Lactic Cultures

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Abstract
Optimal percents of ingredients in phosphate-whey medium for preparing bulk lactic cultures [of streptococci] were determined by multiple regression analysis. The optimum formula included 5.2% whey solids, 0.71% yeast autolysate and 0.43% casein hydrolysate. This formulation increased cell population 36% and culture activity 38% over the control (5% whey solids, 0.4% yeast autolysate, 0.1% casein hydrolysate). Cost analysis suggested no significant advantage of the modified over the control formula. Several media were compared to a commercial phage inhibitory medium for ability to propagate lactic cultures under pH control and protect them during 14 h storage at 27.degree. C. Nonfat dry milk-based media with stimulants added gave more stimulation and provided more protection than commercial phage resistant medium or whey-based blends. Commercial phage inhibitory medium was made comparable by reducing solids to 8% and by adding stimulants. Casein hydrolysate was more stimulatory than intact casein, but the latter was more protective of ripened cultures during 14 h storage at 27.degree. C.