CHARACTERIZATION OF CHEESE RIPENING BY FREE AMINO-ACIDS AND BIOGENIC-AMINES AND INFLUENCE OF BACTOFUGATION AND HEAT-TREATMENT OF MILK

An efficient method for the simultaneous determination of free amino a cids (FAA) and biogenic amines (BA) was applied to the analysis of pre sumed raw milk cheeses of the following types: Emmental (n = 18), Berg kase (n = 28), semi-hard cheeses (n = 18) and soft cheeses (n = 41). T he absolute amounts of FAA and BA largely varied, but the relative amo unts could be classified into four groups independently of cheese type and ripening: i) glutamic acid, lysine, leucine (10-20% of total FAA) ; ii) proline, phenylalanine, valine (6-10%); iii) methionine, alanine , glutamine, isoleucine (3-6%); iv) BA and residual FAA (< 3%). As the formation of BA is strictly dependent on the decarboxylase activity o f microorganisms - raw milk flora, starter, ripening and contaminating bacteria - a large variation within cheese types and even individual cheeses occurred. The use of bactofugated milk for the production of E mmental cheese resulted in a decrease of putrescine and cadaverine, bu t did not significantly influence the formation of histamine and tyram ine. When comparing cheese samples of the same type but from different heat treatments of cheese milk or curd, FAA and BA metabolites showed various tendencies; in particular, BA were not generally reduced upon higher heat treatment. Furthermore, hard cheese samples with strong s ensory defects showed considerable amounts of cadaverine (up to 1800 m g/kg) as well as delta-amino valeric acid (up to 2200 mg/kg), which in regular cheese samples of the same type and age was found to be remar kably lower (100-200 mg/kg). The combined data for FAA and BA provide useful information on cheese ripening and quality control.