Peptide Accumulation and Bitterness in Cheddar Cheese Made Using Single-Strain Lactococcus lactis Starters with Distinct Proteinase Specificities

Abstract

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 OQ 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 aS1-casein (CN), one from b-CN, and one from aS2-CN that accumulated in 6-mo-old cheeses. Most of the peptides derived from aS1-CN (f 1‐23) accumulated in a manner that corresponded with starter proteinase specificity. All of the peptides identified in the study except aS2-CN (f 1‐21) eluted in the O-P-Q region of micellar electrokinetic capillary electropherograms. The aS1-CN (f 1‐16), aS1-CN (f 1‐17) and b-CN (f 193‐209) eluted in peak O, aS1-CN (f 1‐13) and aS1-CN (f 1‐14) eluted in peak P, and aS1-CN (f 1‐9) eluted in peak Q.