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

¹ Minnesota-South Dakota Dairy Foods Research Center, Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108

Commercial cheese products were surveyed for ß-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. ß-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 ß-casomorphins. However, comparison of absorbancies of the peaks at multiple wavelength did not indicate peptides similar to ß-casomorphins. Therefore, ß-casomorphins were absent, or concentrations were below the HPLC detection threshold for ß-casomorphins of 2 µg/ml of cheese extract.

The susceptibility of ß-casomorphins to the proteolytic systems of a commercial strain of Lactococcus lactic ssp. cremoris was investigated. ß-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 ß-casomorphins and the degradation products were monitored over 15 wk using HPLC. Enzymatic degradation of ß-casomorphins was influenced by the combination of pH and salt concentrations at cheese ripening temperatures. Therefore, if formed in cheese, ß-casomorphins may be degraded under conditions common for Cheddar cheese.

Key Words: ßbeta;-casomorphins • cheese proteolysis • Xprolyl dipeptidyl aminopeptidase

Submitted on February 9, 1995
Accepted on September 5, 1995

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