Effects of Lactic Cultures on Acidity and Firmness of Cottage Cheese Coagulum

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Abstract
Nonfat dry milk reconstituted to give 11% solids-not-fat was made into cottage cheese coagulum at 90[degree]F by adding 7% starter and 1 ml rennet/1000 1b. of skim milk. Seventeen different cultures were used. There was a close relationship between pH of curd and curd strength. Regardless of their activity, cultures showed essentially the same relation between curd strength and decrease in pH after coagulation. The 17 cultures varied widely in their relations between curd strength and titratable acidity of whey, and in their relations between pH of curd and titratable acidity of whey. High titratable acidity produced by some cultures at the A-C end point was associated with floating curd during heating. The phenomenon seems to be explained by varied production by the different cultures of weakly ionized acids such as carbonic and acetic acids. The data explain why occasional vats of milk do not coagulate at normal titratable acidity values, and indicate that it is not always desirable to use the same culture for making both cottage cheese and cultured buttermilk.