Effect of freezing prior to ripening on the peptide profile present in the water-soluble fraction at pH 4.6 of a commercial low-fat soft cheese

Freezing was proposed as an alternative preservation technique to extend the shelf life of soft cheeses. However, the freezing process (freezing, frozen storage, and thawing) can affect a number of cheese quality parameters, such as the water-soluble nitrogen content at pH 4.6, which is related to the maturation index of cheeses. The objective of this work was to assess the effect of the freezing process prior to ripening of low-fat soft cheese containing microparticulated whey proteins as fat replacer. The freezing process consisted of freezing at -25 A degrees C, frozen storage at -25 A degrees C during 33 days, and thawing at 6 A degrees C. Refrigerated cheeses, stored at 6 A degrees C, were selected as control samples. High-performance liquid chromatography was used for analyzing the evolution of peptides present in the water-soluble fraction at pH 4.6 at different ripening times. Principal component analysis was applied to reduce the dimensionality of the data obtained from chromatograms. Results indicated that peptide profile was affected by the freezing process. Areas of peaks with hydrophilic characteristics increased during the ripening time, from 1 to 48 days, in both refrigerated and frozen cheeses. Furthermore, areas of hydrophilic peaks were higher in frozen cheeses than in refrigerated cheeses at 21 and 48 days of maturation. However, areas of peaks with hydrophobic characteristics increased in refrigerated cheeses but stayed invariable in frozen cheeses during all the studied ripening periods. In this case, areas of hydrophobic peaks were lower in frozen cheeses than in refrigerated cheeses at the same day of ripening time.