Changes of Free Amino Acid and Nucleotide in Minced Shrimp(Litopenaeus vannamei)during Ohmic Heating

To analyze the effects of different temperatures(40,55,65,75,85 and 95℃)on the main non-volatile taste components of Litopenaeus vannamei during ohmic heating,the free amino acid and nucleotide and related compounds contents in minced shrimp were determined by the amino acid automatic analyzer and high performance liquid chromatograph,respectively. The main taste components and their contribution were evaluated by taste activity value(TAV). Also,the synergistic effect between free amino acids and nucleotides was evaluated by equivalent umami concentration(EUC)method. Results showed that:Compared with fresh shrimp,the total amount of free amino acids in the heat-treated minced shrimp had different degrees of reduction. With the increasing of temperature,the contents of umami amino acid,sweet amino acid and bitter amino acid all decreased first and then increased,and reached the minimum at 65℃(the total TAV value of umami amino acid,sweet amino acid and bitter amino acid were 0.86,4.40 and 4.46,respectively). Ohmic heating did not affect the degradation pathway of ATP,but only changed the relative contents of nucleotides and related compounds,especially to promote the production of Ado. Glycine,arginine,glutamate,AMP and IMP had TAV greater than 1 at different heating temperatures,which was a major contributor to the taste of minced shrimp. The EUC value at 40℃ was 5.54 g MSG/100 g,indicating that this temperature was most helpful for the formation of umami,and the EUC value at 85℃ was 4.02 g MSG/100 g,indicating that the overall flavor loss of minced shrimp was minimal at this temperature.