Effect of commercial adjunct cultures on proteolysis in low-fat Kefalograviera-type cheese

Abstract

The effect of two commercially available adjunct cultures, LBC 80 ( Lactobacillus casei subsp. rhamnosus ) and CR-213 (containing Lactococcus lactis subsp. cremoris and Lc. lactis subsp. lactis ) on the proteolysis in low-fat hard ewes’ milk cheese of Kefalograviera-type was investigated. Two controls, a full-fat cheese (306 g kg −1 fat, 378 g kg −1 moisture) and a low-fat cheese (97 g kg −1 fat, 486 g kg −1 moisture, made using a modified procedure), were also prepared. The effect of adjunct culture on proteolysis, as examined by polyacrylamide gel electrophoresis of cheese and water soluble cheese extracts, was marginal. The reverse-phase HPLC peptide profiles of the water soluble extracts from low-fat cheeses were similar although some quantitative differences were observed between low-fat control cheese and experimental cheeses. The fat content as reflected by the differences in peptide profiles affected the pattern of proteolysis. Proteolysis, as measured by the percentage of total nitrogen soluble in water or in 120 g L −1 trichloroacetic acid, was significantly ( P <0.05) affected by the addition of adjunct cultures. Furthermore, the adjunct cultures enhanced the production of low molecular mass nitrogenous compounds; the levels of total nitrogen, soluble in 50 g L −1 phosphotungstic acid, and of free amino acids were significantly ( P <0.05) higher in the low-fat experimental cheeses than in the low-fat control cheese.