FRACTIONATION OF LOW-MOLECULAR-MASS PEPTIDES IN CHEESE

The repeatability of the fractionation of the water-soluble extract (W SE) of Cheddar cheese by gel permeation chromatography was assessed. T he gel permeation profiles of the diafiltration permeates (DFP) obtain ed from 5 commercial Cheddar cheeses varying in age from 5 to 33 month s were very reproducible, showing some quantitative and qualitative di fferences. Small fractions (10 ml) were collected from the gel permeat ion chromatograms of the DFP. Analysis of the fractions by RP-HPLC sho wed that the collection of 10 ml fractions gave a better separation of some peptides than when larger fractions were pooled although it did not offer a marked improvement for the isolation of individual peptide s. The use of formic acid (50 mM) for the fractionation of cheese nitr ogen was also studied. The preparation of a formic acid-soluble extrac t (FASE) and especially the use of 50 mM formic acid as gel permeation eluent gave a different fractionation of cheese peptides than that ob tained with distilled water, mainly evident in the separation of a hig her number of low molecular mass peptides. For a better assessment of the fractionation, these peptides should be identified.