Semi-Hard Cheeses with Propionic Acid Fermentation

Milk-clotting enzymes with particular proteolytic properties can control gas formation in semi-hard cheeses obtained by propionic acid fermentation. Slow development of propionic acid bacteria and low gas formation result in a poor eye pattern. On the contrary, enhanced early proteolysis provides propionic acid bacteria with enough nutrition to boost their growth. The authors compared the propionic acid fermentation (Propionibacterium freudenreichii ) of semi-hard cheeses made with milk-clotting enzymes with high (600 IMCU/mL) and low (100 IMCU/mL) proteolytic profiles. The degree of proteolysis was detected using the Kjeldahl method and peptide profiles obtained by high-resolution gel filtration (AKTA pure 25, Sweden). The amount of peptides in the water-solublefraction was determined by chromatograms and the peak areas of peptides with different molecular weights. The development rate of propionic acid bacteria correlated with the amount of proteolysis products in cheese, which is known to depend on the proteolytic activity of the milk-clotting enzyme. In this study, milk-clotting enzymes with high proteolytic activity sped up the peptide formation, thus increasing the bacterial count, facilitating gas formation, and developing a stronger eye pattern. A proper ratio of proteolytic activities and the main starter microflora may regulate the process of gas formation in cheeses with propionic acid bacteria.