Free Amino Acid Profiles During Ripening of Port Salut Argentino Cheese After Frozen Storage

Chemical and instrumental approaches to cheese analysis

Overcoming the complexity of cheese matrix to reliably analyze cheese composition, flavor, and ripening changes has been a challenge. Several sample isolation or fractionation methods, chemical and enzymatic assays, and instrumental methods have been developed over the decades. While some of the methods are well established standard methods, some still need to be researched and improved. This chapter reviews the chemical and instrumental methods available to determine cheese composition and monitor biochemical events (e.g., glycolysis, lipolysis, and proteolysis) during cheese ripening that lead to the formation of cheese flavor. Chemical and enzymatic methods available for analysis of cheese composition (fat, protein, lactose, salt, nitrogen content, moisture, etc.) are presented. Electrophoretic, chromatographic, and spectroscopic techniques are also reviewed in the light of their application to monitor cheese ripening and flavor compounds. Novel instrumental methods based on Fourier-transform infrared spectroscopy that are currently being researched and applied to cheese analysis are introduced.

Proteolytic activity of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus in frozen-stored Kashkaval cheese

Proteolytic activity of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus in Kashkaval cheeses of varying aging times, stored at -10 to -12 degrees C for 12 months, was studied. It was established that the proteolysis of Kashkaval cheese induced by the starter culture was significantly delayed by freezing. The noncasein nitrogen (NCN/TN) and nonprotein nitrogen (NPN/TN) as a percentage of total nitrogen increased slightly during frozen storage of Kashkaval. It was found that NCN/TN and NPN/TN values increased to a larger extent in frozen-stored Kashkaval samples with shorter aging time. Enhanced proteolysis was observed during ripening of thawed Kashkaval cheese. There was greater accumulation of noncasein nitrogen in thawed Kashkaval samples compared to the control samples. The enhanced proteolysis during ripening of thawed Kashkaval cheese resulted in larger amounts of high and medium molecular weight peptides and lower amounts of low molecular weight peptides and free amino acids as compared to controls.