凡纳滨对虾虾头自溶动力学

Autolysis kinetics of Litopenaeus vannamei head

研究了温度、pH和底物浓度等对凡纳滨对虾虾头自溶过程的影响,以及自溶产物随自溶时间的变化规律:0～5h内自溶反应产物的溶出遵循一级反应速度方程:Y=39.496e-0.3913x,KP=-1.1464Y+59.506,Pe=-0.7167Y+32.551;溶出总蛋白和5000u以下自溶产物及残余蛋白之间存在很好的线性相关性;自溶过程中,温度、pH、固液比是影响自溶速率常数(Ka)的重要因素。自溶过程中,40～50℃温度范围内,Ka值随温度的升高而增大,50℃时Ka值达最大值,50～60℃,Ka值随温度的升高而减少;pH与固液比对Ka的影响不呈规律性,在pH9、固液比1∶3时Ka值分别达最大值。利用自溶速率常数的对数与绝对温度的倒数建立了Arrhenius方程LnKa=-13654/Tk+41.353,经此方程验证了所建立自溶动力学方程的有效性。在自溶初始阶段(0～1h),5000u以上自溶产物占较大比例,为58%,自溶2～3h5000u以下产物的比例增幅较快,3h时5000u以下产物达66.8%,自溶4～5h后5000u以下产物增加趋缓,为71.47%。自溶过程中,从0h到5h,大部分脂肪族氨基酸溶出2～8倍不等,特别是天门冬氨酸(Asp),自溶前为0.017mg/100mL,自溶5h后含量增加将近8倍,达0.13mg/100mL,谷氨酸(Glu)增加量次之,自溶前为0.041mg/100mL,自溶5h后为0.17mg/100mL;杂环氨基酸脯氨酸(Pro)、组氨酸(His)和含硫氨基酸胱氨酸(Cys)、甲硫氨酸(Met)溶出量较少,特别是胱氨酸(Cys)和脯氨酸(Pro),胱氨酸的平均含量基本保持在0.006～0.009g/100mL,脯氨酸平均含量基本保持在0.07～0.09g/100mL。

This investigation studied the effects of temperature, pH and substrate concentration on the autolysis processing of Litopenaeus vannamei head and the change law of the hydrolysate during the autolysis, a kinetic model of the autolysis reaction process was then established. Our purpose was to monitor autolysis course based on the kinetic model, by which we can not only obtain the anticipative molecular weight autolysate, but also increase protein recovery economically and effectively. The study was conducted to investigate the effects of temperature, pH and substrate concentration on the autolysis process of Litopenaeus vannamei head and the change law of the hydrolysate during the autolysis. The rules of the hydrolysate releasing during the first five hours fitted the first order reaction kinetics： Y = 39. 496e^-0.3913x, KP = -1. 146 4Y＋59. 506, Pe = -0. 716 7Y＋32. 551. It showed a good linear relativity between KP, autolysis hydrolysate under 5 000 u and residual protein. In the course of autolysis, the important factors were temperature, pH and substrate concentration which affect shrimp head autolysis rate. During the autolysis, the value of Ka increased with temperature rising from 40℃ to 50℃ and reached a peak at 50 ℃, while the value of Ka reduced with temperature rising from 50 ℃ to 60℃; the effect of pH and substrate concentration on Ka did not show regularity, the value of Ka reaches a peak at pH9 and substrate concentration 1： 3, respectively. We established an Arrhenius equation LnKa = - 13 654/Tk ＋ 41. 353 and used it to certify the efficacy of the kinetic model. At the beginning of the autolysis （ 0 - 1 h ）, the hydrolysate above 5 000 u took a greater proportion, the percentage was 58% ; the percentage of the hydrolysate under 5 000 u increases rapidly during 2 -3 h, and was up to 66.8% at 3 h, the increase trend slowed down at 4-5 h, the percentage was 71.47%. In the course of autolysis （0 h -5 h）, the release quantity of most of fatty amino acids increased 2 -8 times, the content of aspartic acid is 0.13 mg/100mL after autolysis 5 h while its content was 0.017 mg/100 mL before autolysis; the increase content of glutamic acid followed aspartic acid, the content was 0.17 mg/100 mL after autolysis 5 h and the content was 0. 041 rag/100 mL before autolysis; while the contents of heterocyclic amino acids--praline, histidine and the amino acids contain the group of sulphur like cysteine, methionine were stable, the contents of cysteine and proline kept at 0. 006 -0. 009 g/100 mL and 0.07 -0.09 g/100 mL, respectively. This paper intended to establish a kinetic model to fit the autolysis of Litopenaeus vannarnei head.