通电加热过程中凡纳滨对虾虾肉糜的游离氨基酸和核苷酸含量变化研究

为研究通电加热过程中不同加热温度(40、55、65、75、85和95℃)对凡纳滨对虾虾肉糜中主要非挥发性滋味成分的影响,采用氨基酸自动分析仪和高效液相色谱仪分别检测了虾肉糜中的游离氨基酸和核苷酸及其关联产物含量,并采用味道强度值(TAV)确定其中主要的呈味物质及贡献程度,最后通过味精当量(EUC)分析鲜味氨基酸和呈味核苷酸之间的协同作用,并对其鲜味进行评价。结果表明,与鲜虾相比,通电热处理的虾肉糜中游离氨基酸总量均有不同程度的减少。随着温度的升高,鲜味氨基酸、甜味氨基酸和苦味氨基酸的含量均呈现先减少后增加的趋势,且在65℃达到最小值(鲜味氨基酸、甜味氨基酸和苦味氨基酸的总TAV值分别为0.86、4.40、4.46)。通电加热并不影响ATP的降解途径只是会改变核苷酸及其关联产物的相对含量,尤其是促进Ado的产生。甘氨酸、精氨酸、谷氨酸、AMP和IMP在不同加热温度下其TAV几乎都大于1,是虾肉糜滋味的主要贡献者。味精当量以谷氨酸钠质量计,40℃最能促进虾肉糜鲜味的产生(EUC值为5.54 g MSG/100 g),在85℃处虾肉糜风味损失最小(EUC值为4.02 g MSG/100 g)。

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.