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-strain Lactococcus lactis starters that had distinct cell envelope proteinase specificities. Micellar electrokinetic capillary electrophoresis of aqueous cheese extracts detected three large peaks, designated O, P, and Q, that eluted with peptide standards and increased in area during cheese maturation in a pattern that was distinct for each starter. Regression analysis of bitter flavor scores from trained sensory panels and individual O-Q peak areas suggested that peaks P and Q had a negative and positive correlation, respectively, to this defect. Then, HPLC, capillary electrophoresis, peptide sequencing, and mass spectrometry 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 cheeses. Most of the peptides derived from alpha(S1)-CN (f 1-23) accumulated in a manner that corresponded with starter proteinase specificity. 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) and beta-CN (f 193-209) eluted in peak O, alpha(S1)-CN (f 1-13) and alpha(S1)-CN (f 1-14) eluted in peak P, and alpha(S1)-CN (f 1-9) eluted in peak Q.