β-Casomorphins: Analysis in Cheese and Susceptibility to Proteolytic Enzymes from Lactococcus lactis ssp. cremoris

Abstract

Commercial cheese products were surveyed for β-casomorphin peptides. Two extraction methods were compared: 1) water and 2) chloroform and methanol. Peptide profiles were determined using reverse=phase HPLC and multiple wavelength detection. β-Casomorphin standards were used for comparison with cheese peptide profiles. Results indicated that peptides were present in cheeses with HPLC elution times that were similar to those for β-casomorphins. However, comparison of absorbancies of the peaks at multiple wavelength did not indicate peptides similar to β-casomorphins. Therefore, β-casomorphins were absent, or concentrations were below the HPLC detection threshold for β-casomorphins of 2μg/ml of cheese extract.The susceptibility of β-casomorphins to the proteolytic systems of a commercial strain of Lactococcus lactic ssp. cremoris was investigated. β-Casomorphin standards were incubated at 4°C with bacterial cell lysate at pH 5.0, 5.2, 5.4, and 5.7. Salt concentrations varied among 0, 1.5, and 5%. The concentration of added β-casomorphins and the degradation products were monitored over 15 wk using HPLC. Enzymatic degradation of β-casomorphins was influenced by the combination of pH and salt concentrations at cheese ripening temperatures. Therefore, if formed in cheese, β-casomorphins may be degraded under conditions common for Cheddar cheese.