Contribution of propionic acid bacteria to lipolysis of Emmental cheese

Compared to many cheeses, lipolysis of Emmental is generally low. It concerns about 1-2% of cheese fat and the amount of free fatty acids (FFAs) varies from 2 to 7 g.kg(-1) of ripened cheese. In this work, we studied the extent of lipolysis due to propionic acid bacteria (PAB). The release of FFAs during the ripening of Emmental cheeses made from microfiltered milk, with or without propionic acid bacteria (PAB) was followed. The usual cooking step in the cheese process (up to 50 degreesC and 30 min) inactivated the lipoprotein lipase (EC 3.1.1.34) and the main factor in the lipolysis of Emmental cheese was shown to be the lipolytic activity of PAB. This activity was strain-dependent and not related to the production of propionic acid in cheese. The most abundant FFAs were palmitic acid, oleic acid, myristic acid and stearic acid as in milk fat and it was concluded that lipolytic activity of PAB is non-specific. Lastly, an interaction still not elucidated was evidenced between certain PAB strains and thermophilic lactobacilli strains regarding lipolysis extent in Emmental cheese.