Effect of Proteolytic Activity of Streptococcus cremoris on Cottage Cheese Yields

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Abstract
Using only a proteinase-negative variant of Streptococcus cremoris UC310 to manufacture cottage cheese increased theoretical yields by 2.26% compared with the proteinase-positive parent. Yield differences between positive and negative variants were strain dependent and not detected with variants of UC73 and UC97. Growth of proteinase-negative variants in bulk culture required pH control and addition of sufficient nitrogenous stimulant to provide carry-over activity into the cheese milk. Cultures developed normally when the bulk medium contained 5% of a blend of yeast extract and casein hydrolyzate. Proteinase-negative culture successfully completed acidification of cottage cheese milk after direct acidification to pH 5.2 with phosphoric acid. Lactic culture strain selection is suggested for maximizing product yields with proteinase-negative cultures.