Proteolysis in reduced sodium Feta cheese made by partial substitution of NaCl by KCl

Feta cheeses (five trials) of different sodium content were made, using ewes' milk, from split lots of curd by varying the salting procedure, i.e. dry salting with NaCl (control) or mixtures of NaCl/KCl(3:1 or 1:1, w/w, basis) and filling the cans with brine made with NaCl or the above NaCl/KCl mixtures, respectively. in order to study the influence of the partial substitution of NaCl by KCl on the proteolysis during cheese ripening. The extent and characteristics of proteolysis in the cheeses were monitored during aging by using Kjeldahl determination of soluble nitrogen fractions (water-soluble nitrogen, trichloroacetic acid-soluble nitrogen, phosphotungstic acid-soluble nitrogen), the cadmium-ninhydrin method for the determination of total free amino acids (FAA), urea-polyacrylamide gel electrophoresis of cheese proteins followed by densitometric analysis of the chi (s1)- and beta -casein fractions, reverse-phase HPLC analysis of the water-soluble extracts of cheeses, and ion-exchange HPLC analysis of FAA. The results showed that proteolysis was similar in control and experimental cheeses at all sampling ages, indicating that the partial substitution of NaCl by KCI in the manufacture of Feta cheese had no significant effect on the extent and characteristics of proteolysis during cheese aging. (C) 2001 Elsevier Science Ltd. All rights reserved.