Lactic Bulk Culture System Utilizing Whey-based Bacteriophage Inhibitory Medium and pH Control II. Reduction of Phosphate Requirements under pH Control

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Abstract
Reduction of added phosphates in a bacteriophage inhibitory whey-based medium was possible through the application of pH control. Thirty-five active lactic [streptococcal] strains and homologous bacterio-phage filtrates were inoculated into whey media containing 0-2% added phosphates and continuously neutralized with 20% ammonium hydroxide. At 0% phosphates, all but 5 strains lysed, but improved growth of these was evident in the media containing added phosphates. Twenty-one strains were protected by .5%, 30 by .75%, 34 by 1%, and all 35 by 2% added phosphates. All strains performed better in the whey-based medium than in a commercial bacteriophage inhibitory medium under pH control. Acid production was faster in bacteriophage-challenged cultures with reduced phosphate. Storage of a dehydrated bacteriophage inhibitory medium for 2 yr did not affect propagation characteristics of lactic culture. Examples of individual strain responses to the different phosphate percents are reported. Reduced phosphate enhanced milk clotting time, allowed faster culture development, provided protection against bacteriophage and reduced phosphate content in finished products.