Specificity of Lactococcus lactis subsp cremoris SK11 proteinase, lactocepin III, in low-water-activity, high-salt- concentration humectant systems and its stability compared with that of lactocepin I
Jr. Reid et T. Coolbear, Specificity of Lactococcus lactis subsp cremoris SK11 proteinase, lactocepin III, in low-water-activity, high-salt- concentration humectant systems and its stability compared with that of lactocepin I, APPL ENVIR, 65(7), 1999, pp. 2947-2953
Marked changes in the specificity of hydrolysis of alpha(s1)-, beta-, and k
appa-caseins by lactocepin III from Lactococcus lactis subsp, cremoris SK11
were found in humectant systems giving the equivalent water activity (a(w)
) and salt concentration of cheddar cheese. Correlations were noted between
certain peptides produced by the activity of lactocepin III in the humecta
nt systems and peptides found in cheddar cheese. The stability of lactocepi
n III was compared with that of lactocepin I from L. lactis subsp. cremoris
HP in the humectant systems at different pHs. Significant differences betw
een the stability of each of the lactocepin types were evident. The relatio
nship between stability and humectant type, a(w), pH, and NaCl concentratio
n was complex. Nevertheless, in those systems where a(w), pH, and NaCl conc
entration were equivalent to those in cheddar cheese, lactocepin I was gene
rally more stable than lactocepin III. It was concluded that differences in
the specificity and/or stability of various lactocepin types are likely to
persist in cheese itself and therefore potentially contribute to differenc
es in the peptide composition of ripened cheese.