PEPTIDE ACCUMULATION AND BITTERNESS IN CHEDDAR CHEESE MADE USING SINGLE-STRAIN LACTOCOCCUS-LACTIS STARTERS WITH DISTINCT PROTEINASE SPECIFICITIES

This study investigated peptide accumulation and bitterness in reduced - and full-fat Cheddar cheeses that were manufactured with single-stra in Lactococcus lactis starters that had distinct cell envelope protein ase specificities. Micellar electrokinetic capillary electrophoresis o f aqueous cheese extracts detected three large peaks, designated O, P, and Q, that eluted with peptide standards and increased in area durin g cheese maturation in a pattern that was distinct for each starter. R egression analysis of bitter flavor scores from trained sensory panels and individual O-Q peak areas suggested that peaks P and Q had a nega tive and positive correlation, respectively, to this defect. Then, HPL C, capillary electrophoresis, peptide sequencing, and mass spectrometr y were used to identify five peptides from alpha(S1)-casein (CN), one from beta-CN, and one from alpha(S2)-CN that accumulated in 6-mo-old c heeses. Most of the peptides derived from alpha(S1)-CN (f 1-23) accumu lated in a manner that corresponded with starter proteinase specificit y. All of the peptides identified in the study except alpha(S2)-CN (f 1-21) eluted in the O-P-Q region of micellar electrokinetic capillary electropherograms. The alpha(S1)-CN (f 1-16), alpha(S1)-CN (f 1-17) an d beta-CN (f 193-209) eluted in peak O, alpha(S1)-CN (f 1-13) and alph a(S1)-CN (f 1-14) eluted in peak P, and alpha(S1)-CN (f 1-9) eluted in peak Q.