Comparative study by multivariate statistical analysis of proteolysis in a sodium caseinate solution under cheese-like conditions caused by strains of Lactocaccus

Sonicated cells of Lactcoccus lactis subsp, cremoris 223, 227, SK11, AM1, Wg2 or L. lactis subsp. lactis UC317 were added to a sodium caseinate solution under conditions found in Cheddar or Gouda cheese during ripening (pH 5.25 and 5.0% (w/v) NaCl). Proteolysis was assessed by urea-polyacrylamide gel electrophoresis of the pH 4.6- and ethanol (70%)-insoluble fractions and reverse-phase-high-performance liquid chromatography of the ethanol (70%)-soluble fraction, and the resulting peptide profiles were analysed by principal component analysis and hierarchical cluster analysis. Statistical analysis of peptide profiles of the ethanol (70%)-soluble fraction from 2, 9, 17 or 23 d-old samples grouped the strains into three clusters which were similar to those found earlier for the same strains in an experiment with miniature Cheddar-type model cheeses by Shakeel-Ur-Rehman, Pripp, McSweeney and Fox (1999, Lair, 79, 361-383). (C) 2000 Elsevier Science Ltd.