Influence Of Z-value On Optimization Of Heat Treatment For Cooking

The evaluation and optimization of sterilization process generally takes F value(Sterilization value)as the constraint condition to represent the inactivation of microorganisms,and C value(Cook value)as the objective condition to represent the changes of food quality during thermal processing.The premise of the optimization of sterilization is that the z value of quality factor is greater than the z value of inactivation of microorganisms.The smaller z value indicates the greater sensitivity of inactivation of microorganisms or quality factor to temperature.The z value is determined by kinetic method,which is an objective z value.As the most important technical term of traditional Chinese cuisine,there is not unanimous understanding of“Huohou”in the published literature.In order to express the degree of maturing quantitatively under variations of temperature,several novel kinetics functions are put forward for the cooking process,including maturity value(M value)and overheated value(O value).Thus,“Huohou”was dynamically defined as the cooking operation minimizing the overheated value while ensuring that the cooking value reaches maturity.Due to the Bao and stir-fry's short cooking time resulting in significant unsteady characteristics and drastic changes in food quality,traditional physical and chemical analysis methods can not be used for global analysis and food quality description.Similar to the process of sterilization,the optimization of cooking process generally takes M value as constraint function and O value as objective function.There are the optimal conditions of heat transfer operating for cooking quality in thermal process of liquid-particles in traditional Chinese cuisine only if z _M value of maturity quality factor and z _O value of overheated quality factor are not the same,and the former is less than the latter.The reason is that the mature quality factor(such as protein denaturation)is more sensitive to the changes of temperature than the overheated quality factor(such as color change),so the dishes can reach maturity in a very short time by heating rapidly,while the overheated quality damage is controlled to a certain extent due to the short time.z value is of great significance to the optimization of cooking processing.The more different the z value is,the more significant the optimization is.z _M value was determined by sensory evaluation and kinetic method,which was a subjective z value,while the z _O value is determined by kinetic method,which is an objective z value.It was reported in the literature that when stir-frying garlic sprout and pork tenderloin,the optimal temperature of cooking oil was obtained by numerical simulation and experimental results,which proved the theory of cooking optimization principle.The z _M values of garlic sprout and pork tenderloin were 10?and 30?,respectively.According to the cooking optimization principle,the smaller z _M value means a more significant optimization.Therefore,this paper is to explore the influence of z _M value on optimization and the difficulty of“Huohou”control by finding a more typical and representative food material,and comparing its z _M value with other foods'z _M values.This paper takes pork liver as the research object to carry out cooking process optimization.The results showed that the termination maturity value(M_T)of pork liver was 0.014 min and the maturity quality factor(z _M)was 2?(which was the lowest z _Mvalue determined currently among all kinds of food)determined by sensory evaluation and kinetic method,and the changes of brightness,redness,whiteness,shear force and cooking loss followed a zero order kinetics reaction during stir-frying process,the z values of which are 19.53?,20.61?,20.20?,14.16?and 30.12?respectively,all of them greater than the z _M value of maturity quality factor of pork liver.It can be used as the z _O value of overheated quality factor in the optimization of pork liver cooking.The result of cooking optimization of pork liver with different thickness(3?6 mm)at 100?180?oil temperature showed that the smaller the pork liver thickness,the shorter the cooking time,the better the quality,but the more difficult the“Huohou”control is,and vice versa.It is in line with scientific principles that in this case of meat slices,the most common thickness of which in Chinese cuisine is 2?4 mm,Chinese cooking often uses high-temperature-short-time stir-frying method to handle raw materials sensitive to temperature changes,when the dishes reach maturity,the cooking was terminated immediately,making the formation of overheated quality minimum,so as to get the best quality.The universality and practicability of the control of four“Huohou”index(the maturity time,the maturity rate,the overheated rate,the optimized rate of variation)was proved by calculating the quantitative“Huohou”control indexes of the operation of the oil temperature,thickness and h_fp(Surface heat transfer coefficient)in the process of cooking pork liver.In the case of different z _M value,the smaller the z _M value,the faster the quality change,the more difficult the“Huohou”control is.When it comes to the food raw materials with different z _M value,the difficulty of“Huohou”control can not be explained by the maturity rate and the overheated rate,but by the maturity time and the optimized rate of variation.The“Huohou”control of traditional cooking was based on experience,but quantitative“Huohou”control index only needs to obtain the temperature-time history of cooking process,and then it can be calculated by code,which conforms to the principle of engineering design,and provides theoretical basis and important parameters for the engineering of cooking“Huohou”control.