Effect of slurry incorporation into retentate on proteolysis of Iranian ultrafiltered white cheese

The effect of addition of ripened cheese slurry into retentate on the proteolysis of Iranian ultrafiltered cheese was investigated during 60-day ripening. No significant differences were found in gross composition between experimental samples, however, pH values were significantly higher (P > 0.05) in slurry-containing cheese. Urea-polyacrylamide gel of the pH 4.6 insoluble fractions showed that αs1-casein was hydrolysed more rapidly than β-casein. There was no significant difference in the hydrolysis rate of αs1- and β-casein between the two cheeses. The levels of water soluble nitrogen were significantly higher (P > 0.05) in slurry-containing samples from day 15. The incorporation of ripened slurry into retentate influenced the peptide profiles obtained by RP-HPLC of the pH 4.6-soluble fractions of the cheeses. The ratio of hydrophilic to hydrophobic peptides was higher in slurry-containing cheese. Total and individual free amino acids were significantly higher (P > 0.05) in cheeses containing slurry. It was concluded that the incorporation of ripened cheese slurry into retentate has a beneficial effect on proteolysis acceleration and development of aroma and flavour in Iranian ultrafiltered white cheese.