Effect of frozen storage on free amino acids profile of Port Salut Argentino cheese

VERDINI, RA; ZORRILLA, SE; RUBIOLO, AC

California, USA

Congreso; 2002 IFT Annual Meeting & Food Expo; 2002

Institute of Food Technologists

Port Salut Argentino (PSA) is a soft cheese ripened at 5°C for approximately 30 days. During ripening, peptides and free amino acids are breakdown products of proteolysis that play an important role in flavour and texture of cheeses. Frozen storage, as a preservation technique, is thought to affect cheese structure and proteolysis. Free amino acids profiles characterize protein degradation in each cheese variety, which may be affected by manufacture and storage conditions. Therefore, those profiles are useful to assess the effect of frozen storage on cheese quality. Our objectives were to determine the amino acids that characterize the PSA proteolysis and to evaluate the effect of frozen storage on free amino acids profiles. Fifteen PSA cheeses ripened at 5°C, and fifteen stored at -22°C and then ripened at 5°C were sampled at different ripening times: 1, 6, 13, 27, and 56 days. Considering that salt affects the rate of casein hydrolysis and changes according to position in the cheese, two different sampling zones were considered: central and external zones. Sulfosalisilic acid was used for deproteinization of the water-soluble fraction. Free amino acids were determined by RP-HPLC on the supernatant after precolumn derivatization with o-phtadialdehyde. Principal Component Analysis (PCA) was used to reduce dimensionality and examine data variation.  The major amino acids present in PSA cheese were Leu, Lys, Asn, Phe, Thr, Tyr, Gln, and Val. Cheeses that underwent frozen storage yielded an amino acids profile similar to those of refrigerated cheeses. Two principal components represented 97.2% of the data variation. PCA outlined two major groups of cheese samples: fresh cheeses (1 to 13 days) and ripened cheeses (27 and 56 days). The information presented can help in the design of an appropriate combination of frozen storage and ripening periods to increase preservation time without affecting product quality.