Characterizing the effect of free amino acids and volatile compounds on excessive bitterness and sourness in defective dry-cured ham

Some studies indicated that excessive softness, adhesiveness, bitterness and sourness were the common sensory defects of dry-cured ham, which severely belittled consumers' acceptability. To expound the formation of excessive bitterness and sourness in dry-cured ham, free amino acids, volatile compounds and their metabolic pathways were investigated in normal and defective samples of Jinhua ham. Compared with normal ham, less than 0.85-fold values of total free amino acids were found in defective ham, indicating that free amino acids seemed not to be key contributor of excessive bitterness in defective ham. The contents of hexanal from 5.17% in raw ham increased to 8.57% in normal ham and to 13.91% in defective ham; more than 4-fold profiles in acetic acid, 2-methyl-butanoic acid and 3-methyl-butanoic acid were showed in defective ham than in normal ham, respectively. Metabolic pathway analysis indicated that Strecker degradation of valine, leucine and isoleucine could be the main pathway to develop sourness defects of ham by enhancing carboxylic acids profiles. Partial least square discriminant analysis further demonstrated that 3-methyl-butanoal, 3-methyl-butanoic acid and acetic acid could be the key discrimination between normal and defective hams.