Abstract: The effect of the deep-frying process on the flavor compounds of Shanghai smoked fish was investigated. The volatile compounds were determined by solid phase micro-extraction-gas chromatography-mass spectrometry (SPME-GC-MS), the nucleotide composition was analyzed by high performance liquid chromatography (HPLC) and the amino acid composition was studied using an amino acid analyzer. Additionally, sensory evaluation was performed. The results showed that a total of 58, 64, 79, 78, 75 and 76 volatile compounds were detected in grass carp deep-fried at 140, 155, 170, 185 and 200 ℃ for 8 min, and 75, 75, 78, 74 and 74 volatile compounds in those deep-fried at 170 ℃ for 4, 6, 8, 10 and 12 min, respectively. The contents of 1-octen-3-ol, hexanal and other earthy odor compounds decreased with increasing oil temperature and frying time. 1-Octen-3-ol, hexanal, nonanal, decanal, 2-nonenal, 2-decenal, 2,4-nonadienal, and 2,4-decadienal were identified as key flavor compounds. The contents of adenosine monophosphate (AMP) and inosine monphosphate (IMP) increased, and the content of hypoxanthine (Hx) decreased in grass carp after deep drying. Moreover, the contents of sweet-tasting amino acids increased, and the contents of bitter-tasting amino acids decreased after deep frying. Deep frying at 185 ℃ for 10 min resulted in higher contents of AMP and IMP and lower content of hypoxanthine (Hx) as well as the highest taste intensity of glutamic acid and histidine and the highest total amount of taste-active amino acids, better preserving the taste of grass carp. The deep-fried fish showed the highest sensory score with a good taste and a strong aroma as well as a golden surface.

Key words: deep frying, smoked fish, volatile compounds, nucleotides, free amino acids, sensory evaluation