Release principle of peptides and amino acids during the autolysis of shrimp head from Litopenaeus vannamei after UV-C irradiation stress

Abstract

UV-C irradiation can activate endogenous enzymes in the body of many aquatic animals. Autolysis kinetics of shrimp head after UV-C irradiation stress was investigated. During the first 5 hr of autolysis, the release of the autolysis products was in line with the first-order equations of the reaction rate: Y = 37.681e−0.173t, Pe = −1.769Y + 74.156, and TP = −1.5117Y + 60.866. A good linear correlation was founded between the release of total protein and that of products with molecular weight of 3,000 Da after these products associated with residual total protein were autolyzed. In contrast to the inconsistent effect of substrate concentration on autolysis rate constants, the effects of pH and temperature on the autolysis rate constants of shrimp head showed a consistent pattern. An Arrhenius equation (lnKa = 8,090.2/T − 26.497) was established to validate the proposed autolysis kinetic equations. The autolysis rate of products with molecular weight < 3,000 Da increased rapidly from 0 hr to 3 hr. The aliphatic amino acids showed a higher amount release than that of other amino acids during the autolysis. The amounts of released heterocyclic amino acids (Trp and His) were also much more than that of other amino acids.