Dairy Foods : Cheese and chemistry 556 Release of bioactive peptides and essential amino acids as affected by sodium chloride reduction and substitution in Akawi cheese

The aim of this study was to evaluate the effects of sodium chloride reduction and its substitution with potassium chloride on selected probiotic bacteria and their functionality in Akawi cheese during storage for 30 d at 4°C. The survival of selected probiotic bacteria (Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium longum) and starter bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus), the angiotensin-converting enzyme-inhibitory and antioxidant activities, and the concentrations of essential amino acids as affected by storage in different brine solutions [10% NaCl, 7.5% NaCl, 7.5% NaCl+KCl (1:1), 5% NaCl and 5% NaCl+KCl (1:1)] were investigated. Peptide profiles of cheese extracts, from different salt concentrations, were observed by RP-HPLC and in vitro bioactivities of the peptide fractions were evaluated using Caco-2 cell line. Survival of probiotic bacteria increased significantly in cheeses with low salt after 30 d, and after 20 d for starter bacteria. No significant difference in texture profile of cheeses during 30-d storage was observed except for fracturability and gumminess, which was found to be lesser in cheeses brined with only NaCl solutions. No significant changes were observed in ACEinhibitory activity and antioxidant activity of the cheeses during storage. Interestingly, concentrations of 4 essential amino acids (phenylalanine, tryptophan, valine and leucine) increased significantly during storage in brine solutions containing 7.5% (w/v) total salt. The study revealed that at total salt concentration of 7.5% (w/v), 50% substitution of NaCl with KCl in Akawi cheese would not affect the activities of potential bioactive peptides, and would lead to increased release of essential amino acids.