中式烹饪用时间温度积分器的构建与验证

蛋白质变性能够较广泛地表征烹饪加热品质变化,因而寻找到一种z值为7.36℃的耐高温α-淀粉酶,与蛋白质热变性z值5~10℃相近。以该酶溶液为指示剂,在玻璃毛细管中封装后置入烹饪耐受性高的、特定形状的魔芋凝胶(g-KGM)载体,从而构建了烹饪研究用时间温度积分器(time temperature integrators,TTIs)装置。随后,在模拟烹饪过程而设定的对流传热条件下,通过传热学试验结合非稳态传热以及酶失活动力学数学模型计算得到剩余酶活,与TTIs装置指示剂酶活实测值比较,两者误差小于2.24%。进一步,应用该TTIs装置测定了实际烹饪爆炒过程的表面换热系数。所构建的TTIs装置,结合数值模拟,可以分析测量常规试验传热学方法无法应用的激烈烹饪中流体-颗粒的传热过程,也可应用于其他领域的移动颗粒传热学研究。

Establishment and verification of time-temperature integrators for Chinese cuisine

Chinese cuisine is regarded as a kind of traditional artistry that has multiple genres, various cooking methods and complicated cooking skills. Stir-frying, a typical operation in Chinese cuisine, normally has the characteristics of short time and drastic stirring. Due to the drastic stirring, food particles rapidly move, so common research methods cannot be used to investigate the internal temperature-time relationship of particles in liquid-particle heat transfer process by this operation, such as the thermocouple method and the numerical simulation method, both of which are limited to determine heat transfer coefficient. In order to realize the standardization and automation of Chinese cuisine, it is necessary to master the changing rules of heat transfer and quality during cooking process, and therefore, time-temperature integrators (TTIs) and the corresponding heat transfer - kinetics mathematical model are crucial or even indispensable methods for the researches on quality changes of cooking. The time-temperature integrator, a small equipment composed of an indicator and a carrier, was used to simulate the changes of target quality parameters, time and temperature history as well as food analogues. Therefore, the indicator must have key quality factors that are similar to kinetic parameters in real food materials, and the shape of food analogues must have similar thermal physical properties to real food system. Protein denaturation is widely used to represent quality changes in cooking process. Surprisingly, a kind of thermostableα amylase with the similarz value (7.36℃ ) to protein denaturation (5-10℃ ) was discoveredand successfully applied as an indicator in our experiment. Specifically, the indicator was encapsulated in a capillary tube and then embedded in a carrier with particular shape for establishing TTIs. The carrier was made of konjac glucomannan gel (g-KGM) which has superior heat resisting property. Subsequently, to simulate cooking process of liquid-particle food under the specific heat transfer condition, the changes of enzyme activity were determined by TTIs, and the theoretical temperature-time relationship was calculated with the unsteady heat transfer mathematical model and then compared with practical experimental results. The temperature curve with the minimal gap of theoretical and actual value was obtained on the basis of the least summation of the squared temperature difference for overall target (LSTD). Finally, the residual activity ofα amylase was obtained based on kinetics methods. And the difference with the measured enzyme activity was not more than 2.24%, indicating the TTIs mathematical model was accurate and reliable. Furthermore, the TTIs mathematical model was used to determine the heat transfer coefficient during stir-frying process of Chinese cuisine. The results showed that the TTIs combined with numerical simulation was appropriate for analyzing and measuring heat transfer process, even for the situations conventional heat transfer experiment method was powerless or some other stormy cooking process with liquid-particle. In addition, armed with quality change kinetics, the heat transfer could be analyzed especially for heated treatment of liquid-particle. That is to say, this method may provide key technology for procedure analysis and process optimization of Chinese cuisine. Moreover, it can also be applied to those studies on actual heat transfer process of moving particles in other field.