Influence of brine immersion and vacuum packaging on the chemistry, biochemistry, and microstructure of Mihalic cheese made using sheep’s milk during ripening

Abstract

Due to practical and hygienic uses in storage and marketing, cheese maker preference for the use of vacuum packaging instead of the brining method has increased significantly in recent years. The objective of the paper was to study and compare the chemistry, biochemistry, and microstructure of Mihalic cheeses ripened in vacuum packaging or under brine over 360 days. Proteolysis in Mihalic cheese was quite low (e.g., pH 4.6 soluble nitrogen was lower than 15%, as a percentage of the total nitrogen, and αs1-casein was slower in comparison to other brined cheeses) due to its high salt-in-moisture and low moisture contents. Urea-PAGE patterns of the pH 4.6 insoluble fractions of the cheeses showed different degradation patterns of αs1-casein in cheeses of different ages. However, β-casein was relatively resistant to hydrolysis. Packaging the cheese in polyethylene bags significantly increased the levels of pH 4.6 soluble nitrogen, 12% trichloroacetic acid-soluble nitrogen, and free amino acids compared to the cheeses ripened in brine. The total concentrations of free amino acids (FAA) in cheeses increased after 120 days of ripening, and Glu, Val, Leu, Lys, and Phe were the most abundant FAA in the cheeses. Higher levels of these AAs were found in the cheeses ripened in polyethylene bags. The peptide profiles by reversed-phase high-performance liquid chromatography of 70% (v/v) ethanol-soluble and ethanol-insoluble fractions of the pH 4.6 soluble fraction of the cheeses revealed that slight differences were found in the levels of some peptides between cheeses. Majority of the volatile compounds were present at higher concentrations in vacuum-packaged cheeses than in those ripened in brines. The images obtained by scanning electron microscopy of the cheeses ripened in polyethylene bags were clearly different (the protein matrix was more compact) from those of brine-ripened cheeses. The cheese ripened in vacuum packaging was completely different in terms of chemical composition, proteolysis, volatile composition, and microstructure. It was concluded that the vacuum packaging may be useful to maintain the chemical and biochemical qualities of Mihalic cheese, and it is also an easy practice during ripening.