The effect of low pressure-homogenized lactic cultures on the development of proteolysis in cheese slurry

Abstract

The aim of this study was to determine the effect of low pressure-homogenization of lactic acid bacteria (LAB) on the development of proteolysis in the slurry medium. For the slurry, the milk was pasteurized at 65 °C for 30 min, cooled to 32 °C and coagulated. The curd obtained was blended; the dry matter was adjusted to 30% by adding distilled water, placed into the flasks and autoclaved. The LAB Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and Lactobacillus helveticus were used in cheese slurry. Homogenization was performed at 30 MPa and 40 °C. The cheese slurries were incubated with and without homogenized cultures at 9 and 30 °C for up to 72 h. During incubation, the changes in trichloroacetic acid-soluble nitrogen (TCA-SN) and phosphotungstic acid-soluble nitrogen (PTA-SN) as well as pH were monitored. The results showed that pH development was slower in the slurries to which homogenized culture was added. Higher TCA-SN and PTA-SN values were obtained from the slurries incubated at 30 °C. Moreover, higher TCA-SN and PTA-SN values were found in the slurries incubated with homogenized mesophilic culture and Lb. helveticus (P<0.05). The results suggested that homogenization of the cultures was a promising method for the acceleration of cheese ripening.