Preparation And Application Of Time Temperature Indicator Based On Polydiacetylene

Perishable food is highly sensitive to temperature.Low temperature storage can effectively extend the shelf life of food,but once the temperature is higher than the required temperature,it will accelerate the loss of food quality and reach the end of shelf life ahead of time.Time temperature indicator(TTI)can directly display the cumulative effect of temperature and time,and can be used to indicate the real-time quality of food.In this study,based on the principle of the responsive color response of polyacetylene liposomes,the gel microspheres were immobilized onto the immobilized liposomes combined with the internal emulsification method.The time temperature indicator was developed by mixing with Tween 20 solution,and its chromogenic characteristics were studied.The main research contents are as follows:(1)The color change response characteristics of polydiacetylene were explored.Two diacetylene monomers,10,12-pentadecadienoic acid(PCDA)and 10,12-tridecadienoic acid(TCDA),were used to prepare liposome solutions.The color transition temperatures of PCDA and TCDA were 65℃ and 55℃ respectively,which were close to their melting temperatures.Raman spectra show that thermal stimulation affects the conjugation length of polydiacetylene.To explore the influence of surfactant types on the color change of polydiacetylene,the nonionic surfactant Tween 20 can make the color change of polydiacetylene from blue to red at lower temperature;(2)The preparation method of TTI and its color changing characteristics were selected.The gel microspheres were used to immobilize the liposomes.The size distribution of microspheres was homogeneous.TTI was composed of gel beads coated with two acetylene liposomes and Tween 20 solution.According to the concentration and temperature of Tween solution,the TTI was discussed that the higher the temperature is,the higher the surfactant concentration is,the faster the discoloration rate and the greater the discoloration degree of TTI are;(3)The color dynamic characteristics of TTIs were explored.The concentration of liposome solution and Tween 20 solution was reduced accordingly,and TTI based on two kinds of diacetylene monomer and two kinds of Tween 20 concentration was prepared.Four color parameters were fitted and analyzed,and the color difference value was selected as the color response parameter of TTI.The activation energies of TTI with different ratios were 150.37 k J/mol,214.40 k J/mol,71.03 k J/mol and 77.43 k J/mol,respectively(4)The activation energy and shelf life of salmon were determined.By measuring the changes of three quality parameters of salmon with time at different temperatures,the change rate of total bacterial count and TBA value of salmon at the corresponding temperature was obtained,and the total bacterial count which reached the limit value faster was selected as the quality index to indicate the freshness of salmon.Finally,the activation energy of salmon was86.54 k J/mol and the shelf life at different temperatures;(5)The matching effect of TTI and salmon was explored.The activation energy and indicator time of TTI were compared with the activation energy and shelf life of salmon.In order to explore the matching effect of salmon and TTI,temperature experiments were carried out under the same conditions.The results showed that the TTI accurately visualize the shelf life of salmon.The innovation lies in the use of endogenous emulsification method to immobilize liposomes to prevent the aggregation and precipitation of liposomes.Through the combination of different kinds of polydiacetylene liposomes and different concentrations of Tween 20 solution,the activation energy of TTI is quite different,which expands its application scope.