Evaluation of commercial adjuncts for use in cheese ripening: 4. Comparison between attenuated and not attenuated lactobacilli

The influence of heat-shocking and freeze-shocking on cell viability, autolytic properties, aminopeptidase, esterase activities and acid production of Lb. helveticus and Lb. casei was studied in buffer and in a cheese slurry system. Heat­ shocking had the most destructive effect on cell viability. The rate of acid production in milk was a function of the attenua­ tion method. Among all strains of lactobacilli, Lb. helveticus I had the least acid production. Heat-shocking was the most effective treatment in reducing acid production. Two cycles of freeze thawing were the most effective treatment in promot­ ing cell autolysis. Heat-shocking had the most detrimental effect on the% autolysis and on the levels of enzymatic activity. The not attenuated cells showed the highest levels of enzymatic activities followed by the freeze-shocked cells and the heat-shocked cells. Cheese slurry containing added freeze-shocked cells of Lb. he/veticus I showed considerably higher levels of peptidase activity release and higher rate of proteolysis compared to the Lb. casei strains.The cheese slurry in­ oculated with freeze-shocked cells ofLb. helveticus I had the most Cheddar flavor.