Effect of Aminopeptidase Activity of Thermophilic Lactobacilli on Emmental Cheese Characteristics

Abstract

Cheeses were made with Lactobacillus helveticus strain L1, which has high aminopeptidase activity, and two clones (L2, L3), selected for their lack of aminopeptidase activity. Strains L2 and L3 were obtained from L1 by mutagenesis. The differences observed in cheese were essentially due to the variation of the aminopeptidase activity, the only parameter varying according to treatments. The physicochemical analyses of cheeses showed no differences in acidification, moisture of curd, and casein degradation. Differences between ripened cheeses were observed only by sensorial analysis; cheeses made with aminopeptidase-deficient lactobacilli (L2, L3) were more stiff and more bitter than those made with L1. The mutants should not be considered as bitter peptide-producing clones, but rather as allowing an accumulation of this kind of peptides in cheeses. These results explain the bitterness in ripened cheeses made with some strains or species of Lactobacillus (e.g., Lactobacillus delbrueckii ssp. lactis) that have a very low aminopeptidase activity. Therefore, the aminopeptidase activity must be controlled when strains of lactic acid bacteria are intended for manufacture of cheese. © 1994, American Dairy Science Association. All rights reserved.