Formation of amino acid-derived volatile compounds in dry-cured mackerel (Scomberomorus niphonius): Metabolic pathways involving microorganisms, precursors, and intermediates.

This study focuses on the formation mechanism of amino acid-derived volatile compounds (AAVC) in dry-cured mackerel (Scomberomorus niphonius) (DCM) during the process. Three kind of AAVC (3-methylbutanal, 3-methylbutanol, and phenylacetaldehyde) were detected in DCM. The content of 3-methylbutanal (14.6 mg/kg) was higher than that of phenylacetaldehyde (12.9 mg/kg), and part of which was reduced to 3-methylbutanol (5.15 mg/kg). While the corresponding intermediate, α-ketoisocaproate (156 μg/kg), was lower than that of phenylpyruvic acid (271 μg/kg), indicating its decarboxylation was limited. Five strains (Bacillus, Enterobacter, Staphylococcus, Macrococcus, and Lactobacillus) that can produce the relative transaminases and decarboxylases were involved in the production of AAVC. The most dominant strain, Bacillus (81.9%), was only involved in the production of 3-methylbutanal. The relative abundance of Staphylococcus, the sole phenylpyruvate decarboxylase-producing bacteria, was low, resulting in low product conversion. These results indicated that the production of AAVC is determined by specific microorganisms in the products.