Proteolysis and production of biogenic amines in Toma Piemontese PDO cheese during ripening

Proteolysis of Toma Piemontese PDO cheese (large/long-ripened cheese and small/short-ripened cheese types) during ripening was studied by monitoring changes in nitrogenous compounds (protein content, SDS-PAGE, pH 4.6 soluble-nitrogen and ripening index). Changes in the concentration of four biogenic amines and their precursor amino acids were also determined, showing the presence of histamine and tyramine (up to a total concentration of 145 mg kg(-1)) in long-ripened cheese. The total concentration of biogenic amines in the commercial samples analyzed did not exceed 219 mg kg(-1). In comparison to short-ripened Toma, long-ripened Toma had a higher level of proteolysis (ripening index up to 20.8% after 64 days ripening) with the characteristic disappearance of the alpha(s1)-casein band in the electrophoresis profiles. The increase in proteolysis during ripening was confirmed by PCA, showing the possibility of using this technique to assess the age of unknown cheese samples. The main variables contributing to the first principal component were ripening index, % soluble N, phenylalanine and alpha(s1)-casein.