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Effect of Gas-Producing Cultures on Titratable Acidity and pH in Making Cottage Cheese^1,2,

Food Research Institute, Research Branch, Agriculture Canada, Ottawa, Ontario K1A 0C6

ABSTRACT

Cultures varied markedly in the amount of volatile acid produced during cottage cheese making. Titratable acidities of whey from 25 cultures ranged from .44 to .62% at pH 4.80 in the curd. Heating whey to boiling reduced acidities to a range of .43 to .49%; higher percents were associated with higher acidities of unheated whey. Shaking or agitation of the whey reduced acidities of wheys almost as much as heating to boiling. Acidities of unheated and heated wheys were proportionally higher from reconstituted skim milks of increasing total solids (8.5 to 12%).

In cottage cheese making, curd of uniform quality was produced by cutting either at pH 4.80 or at a heated whey acidity of .43 to .45%. Unheated whey acidities from gas-producing cultures at pH 4.80 were variable. Cutting at a whey acidity of .50% with nongas-producing cultures resulted in a cutting pH of 4.60 and soft curd. If titratable acidity of whey must be used for determining cutting time, it is recommended either to heat to boiling or to agitate the whey before titration.

Variable production of carbon dioxide by cultures would result in variable titratable acidities of cultured milk products in general. Titration before and after shaking or heating may be useful in estimating the content of carbon dioxide in cultured products and as a control procedure in their production.

¹ Contribution No. 572 from the Food Research Institute.

² A brief summary of the paper appeared as a short communication to the XVII International Dairy Congress in Melbourne, 1970 (1).