The Effect of Homogenized Lactic Cultures on the Development of Proteolysis in Kashar Cheese

Abstract

The goal of the study was to determine the effect of homogenization of lactic cultures at 30 MPa on the development of proteolysis in Kashar cheese during ripening. The cultures Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cemoris, Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus and Lactobacillus helveticus were used in the study. After propagation, the cultures were homogenized at 30 MPa and 40 degrees C for 5 cycles. Cow milk was used to make Kashar cheese in the study. The cheeses were ripened at 8 +/- 1 degrees C for 90 days. Chemical analyses, determinations of water soluble nitrogen (WSN), trichloroacetic acid-soluble nitrogen (TCA-SN) and phosphotungsticacid-soluble nitrogen (PTA-SN) contents and electrophoresis of casein bands were done on days 3, 30, 60 and 90. The results indicated that there was no significant effect of homogenization of the cultures on the chemical composition of Kashar cheeses (P>0.05). However, higher proteolysis values measured as WSN, TCA-SN, and PTA-SN were obtained from homogenized culture-added cheeses. Accumulation of PTA-SN content in the cheeses was significantly (P< 0.05) affected by homogenization of the cultures. At the end of ripening, the homogenized culture-added cheeses had lower residual alpha(s1)- and beta-caseins than the unhomogenized culture-added ones. The effect of homogenization of the cultures on the breakdown of alpha(s1)-casein was significant (P<0.05).