title: Beta-casomorphins: analysis in cheese and susceptibility to proteolytic enzymes from Lactococcus lactis ssp. cremoris.
abstract: Commercial cheese products were surveyed for beta-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. beta-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 beta-casomorphins. However, comparison of absorbancies of the peaks at multiple wavelengths did not indicate peptides similar to beta-casomorphins. Therefore, beta-casomorphins were absent, or concentrations were below the HPLC detection threshold for beta-casomorphin of 2 micrograms/ml of cheese extract. The susceptibility of beta-casomorphins to the proteolytic system of a commercial strain of Lactococcus lactis ssp. cremoris was investigated. beta-Casomorphin standards were incubated at 4 degrees 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 beta-casomorphins and the degradation products were monitored over 15 wk using HPLC. Enzymatic degradation of beta-casomorphins was influenced by the combination of pH and salt concentrations at cheese ripening temperatures. Therefore, if formed in cheese, beta-casomorphins may be degraded under conditions common for Cheddar cheese.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Muehlenkamp
authors.forename: J J
authors.initials: JJ
authors.lastname: Warthesen
mesh_terms: D000595:Amino Acid Sequence; D002611:Cheese / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D010450:Endopeptidases / Q000378:metabolism*; D004723:Endorphins / Q000032:analysis* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D013294:Lactococcus lactis / Q000201:enzymology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism
chemical_list: D004723:Endorphins; D010446:Peptide Fragments; C021968:beta-casomorphins; D010450:Endopeptidases