The Heat Resistance of Lactobacilli found in American Cheddar Cheese

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Abstract
The heat resistance of 60 Lactobacillus cultures found in Cheddar cheese varied within wide limits. Approx. 83% of these organisms which were found in Cheddar cheese made from raw milk could be killed in 30 min. or less at 145[degree]F. The lactobacilli found in Cheddar cheese made from pasteurized milk were much more heat-resistant, having a thermal death time of from 10 to 35 min. at 154[degree]F. The s values, i.e., the temp. increase in degrees F. necessary to reduce the death time 1/10, varied in a general way with the heat resistance of the organisms. The destruction of lactobacilli by pasteurization suggests the possibility of accelerating the ripening of Cheddar cheese made from pasteurized milk either by (1) adding the proper Lactobacillus culture to the milk, or (2) raising the ripening temp. of the cheese. The higher temp. of ripening would supply more favorable growing conditions for the reduced numbers of lactobacilli that survive pasteurization.