Study On Time-Temperature Indicator Based On Alkaline Lipase

At present, food quality and safety is an important problem which has been paid wide attention. Food quality is influenced by internal factors and external environment conditions . Temperature is a relatively high unpredictable factor in all external environment conditions, and fluctuates with the change of environment. If the control of storage environment temperature is unsuitable, food will corrupt, which will induce economic loss. Through an easily measurable mechanical commutation deformation or change of color, time-temperature indicator can reflect the full or partial temperature history of a food product to which it is attached and indicate the remaining shelf life of the food. This experiment was researched a time-temperature indicator based on enzymatic reaction, was established the time-temperature indicator reaction system, determined the kinetic parameters of the reaction system and designed and made the time-temperature indicator. The contents and results are as follows.1. Based of on theoretical of lipase enzymatic hydrolysis, this experiment was studied the effects of the kind of substrate, concentration of substrate, emulsifier and metal ions on reaction system . According to the change of reaction system pH, a proper pH indicator to indicate the change of system color was selected. Through the experiment, the most optimal reacting system of the alkaline lipase was established. Finally, parameters were developed in the reaction system of alkaline lipase time-temperature indicator: 0.1 mL 1g·L^-1 alkaline lipase, 0.5 mL triacetin as enzyme-substrate, 9.5 mL 20 g·L^-1 polyvinyl alcohol (PVA) as emulsifier, 39 mL Gly-NaOH buffer 0.05 mol·L^-1 at pH10.6, 0.7 mL 1 mol·L^-1 calcium chloride solution, 0.2 mL mixture indicator which contained phenol red, phenolphthalein, and thymolphthalein.2. Based on composition of alkaline lipase reaction system, the experiment was conducted under isothermal conditions, The time-temperature indicator system reacted at six constant temperatures, which are 4,10,15,20,25 and 30℃, and through measuring the pH change curve of reaction system to determine the reaction function and kinetic parameters. The activation energy of the TTI reaction system from the different temperature coefficient of the rate constants was found to be 44.85 kJ·mol^-1, and the pre-exponential factor was 1.02×10⁶ h^-1. This system can be applied to monitor the food quality, which decline because of enzymic and lipid oxidation.3. According to characteristics of alkaline lipase reaction system, we designed the time-temperature indicator. The time-temperature indicator reaction system was packaged and used as time-temperature indicator, with the advantage of easy to active, high accuracy, practical, convenient and so on. The time-temperature indicator can be used to indicate the time temperature cumulative effect of goods in cold chain and is convenient to optimize the goods sale and inventory turnover and to ensure the safety of food.