Proteolytic activity of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus in frozen-stored Kashkaval cheese

Abstract

Proteolytic activity of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus in Kashkaval cheeses of varying aging times, stored at -10 to -12 degrees C for 12 months, was studied. It was established that the proteolysis of Kashkaval cheese induced by the starter culture was significantly delayed by freezing. The noncasein nitrogen (NCN/TN) and nonprotein nitrogen (NPN/TN) as a percentage of total nitrogen increased slightly during frozen storage of Kashkaval. It was found that NCN/TN and NPN/TN values increased to a larger extent in frozen-stored Kashkaval samples with shorter aging time. Enhanced proteolysis was observed during ripening of thawed Kashkaval cheese. There was greater accumulation of noncasein nitrogen in thawed Kashkaval samples compared to the control samples. The enhanced proteolysis during ripening of thawed Kashkaval cheese resulted in larger amounts of high and medium molecular weight peptides and lower amounts of low molecular weight peptides and free amino acids as compared to controls.