Research On Time Temperature Indicator Based On Enzyme Reaction

With the improvement of the quality of life, people will pay more attention to the security of the food. Shelf-life issue is an important aspect of food safety, and temperature on the impact of shelf-life is essential, especially for the food affected by the temperature greatly. So the shelf-life on the packaging is determined under certain conditions, but during actual transporting and storing time, the temperature may be changing, thus the shelf-life of food is not accurate. So for ensuring the quality of food, the time temperature indicator (TTI) comes into being. It can simulate the metamorphic process of food and indicate the quality of food.At present, TTI in foreign markets is mainly based on enzyme, diffusion, chemical and electronic. TTI was applied to indicating the quality of meat, milk, mushroom, blood and other perishable food. It is also applied to certain areas of logistics and testing of high temperature sterilization. But in China, the research on the TTI has just begun. This research mainly focuses on developing a TTI based on alkaline lipase reaction, designing the structure of the TTI and studying the kinetic parameters and application of TTI.This research mainly includes:(1) This research developed a TTI based on alkaline lipase reaction. This TTI indicates the reaction degree through the changed color ring. The 0.5% neutral red is determined as the PH indicator of the TTI. Through the orthogonal test the scope of some prescription is determined: agar is 0.01g/ml-0.015g/ml, the proportion of substrate and buffer is about 4.5%, Concentration of lipase enzyme is above 0.02g/m or be determined by the proportion of substrate and buffer, the hole diameter of agar plate is 11mm amd the thick of agar plate is 3mm.(2)Two structures were designed: horizontal TTI and vertical TTI. These two indicators are sensitive, convenient and easy to activate and storage.(3) Dynamic characteristics of nine different TTIs have been studied through the orthogonal experiment. The activation energy (Ea) of TTIs was range from 30 to 100kJ/mol. The effect of proportion of substrate and buffer, agar, Concentration of lipase enzyme and the amount of enzyme on the activation energy (Ea) of TTIs is analyzed and relevant model was established. Besides, the relationship of time-temperature-response value was studied and the relation model of them is established.(4) The metamorphism mechanism and kinetic parameters of milk is studied. Five TTIs has been developed according the Ea of the milk. The kinetic parameters of these five TTIs have been analyzed in three different temperatures and the stability of TTIs also was studied. Besides, the application of the TTI on the milk was studied. The TTI2 (proportion of substrate and buffer 4.5%, agar 0.014g/ml, Concentration of lipase enzyme 0.05g/m, amount of enzyme0.10ml) is the most suitable TTI for the milk.