Food Quality Monitoring Based On Gold Nano Time-temperature Indicator

The market economy is developing rapidly.People pay more and more attention to food safety.Temperature is particularly important for many perishable products.Therefore,the time temperature indicator,which can accurately monitor the temperature and time history of food at any time,has emerged as the times require.It can be used to predict the shelf life of food and protect the health of the people.At present,there are a wide range of TTI types at home and abroad,mainly including diffusion type TTI,microbial type TTI,enzyme type TTI and polymerization type TTI.Many TTI have been commercialized for monitoring the quality of meat,fish,fresh milk,fruit and other products.In addition,gold nanomaterials have been proved to be a time temperature indicator because of their unique optical properties,but their research only stays at the mechanism level.How to prepare a time temperature indicator suitable for commercial application is of great significance.On the basis of previous studies,the reaction of tetrachloroacetic acid tetrahydrate with natural polysaccharide was used to complete the indicator of time temperature,and its kinetic properties and food applications were studied.This research mainly includes:(1)To compare the effect of different reducing agents on the discoloration of TTI,gelatin was selected as the matrix.Based on the solution of tetrachloroalbuminic acid tetrahydrate,sodium alginate,chitosan and gelatin were selected as reducing agents respectively.Gold nanoparticles were formed by reduction method to explore the discoloration effect of TTI under different reducing agents.The results showed that both alginate TTI and chitosan TTI had fading phenomenon,while gelatin TTI had better discoloration effect,the color gradually became darker,and the color change process was clear and easy to judge.Finally,the optimal reducing agent for the preparation of gold nano TTI was found,that is,gelatin was used as the reducing agent to prepare gold nanoparticles.(2)The relationship between preparation parameters and discoloration effect was studied.Using gelatin as both reducing agent and stabilizer,the liquid gold nano time temperature indicator was developed.The influence of preparation parameters on TTI system was studied by single factor experiment.That is to say,for the time temperature indicator with the mass ratio of gelatin to tetrachloroalbuminic acid tetrahydrate of 15,precipitation would occur,and the color of the end point of discoloration was linearly related to the temperature.When the mass ratio of gelatin to tetrachloroalbuminic acid tetrahydrate was 75,TTI system was stable There is no precipitation in the clarification,and the end color of discoloration is basically the same at different temperatures.(3)Colloidal gold nano type TTI was prepared and its kinetic properties were investigated.Based on the conclusion of liquid TTI,colloidal gold nano time temperature indicator was prepared,and its reaction rate,discoloration life and activation energy were studied.The reduction and aggregation rate of gold atoms affect the formation rate of gold nanoparticles,which determines the change rate of TTI absorbance.With the increase of the mass ratio of gelatin to tetrachloroalbuminic acid tetrahydrate,the reduction rate of gold atoms increases,but the agglomeration rate of gold atoms decreases.The interaction of the two determines the activation energy.The activation energies of the five colloidal TTI are relatively concentrated,ranging from 77.89 to 84.58 k J/mol,which can be used to monitor fat rich foods.The TTI has the advantages of simple preparation,convenient use and stable performance.(4)The deterioration model of Muffin Cake was explored and matched with colloidal gold nano time temperature indicator.The Muffin Cake sold in supermarkets at room temperature was selected as the matching object.The deterioration law and dynamic performance of Muffin Cake were studied.The activation energy of Muffin Cake deterioration due to oil oxidation was 92.61 k J/mol.the applicability of colloidal gold nano time temperature indicator and Muffin Cake was studied under constant and variable temperature conditions(temperature range: 15 °C?25 °C).The results showed that TTI with the concentration of 150.00 mg/ml gelatin solution and 2.05 mg/ml tetrachloroacetic acid tetrahydrate solution could accurately monitor the quality change of Muffin Cake.The initial color of TTI was light yellow,which indicated that Muffin Cake was fresh,gradually deepened with time and temperature,and finally changed to dark purple,which indicated that Muffin Cake was inedible.The innovation of this project is to explore the influence of the mass ratio of gelatin and tetrachloroacetic acid tetrahydrate on the discoloration effect of time temperature indicator.The TTI with low mass ratio will produce precipitation,and the color of discoloration end point is linearly related to the temperature.The TTI with high mass ratio has no precipitation,and its discoloration end point color is basically the same at different temperatures.The colloidal TTI prepared has concentrated activation energy,which can match the food deteriorated by fat oxidation.