Preparation Of Anthocyanin Intelligent Colorimetric Films And Application In Freshness Detection

The intelligent packaging technologies used for monitoring food quality mainly include indicators,data carrier devices,sensors and so on.The state of food can be known according to the color response of the indicator in response to the characteristic gas released as the food freshness changes,and the quality or freshness of packaged food can be evaluated in real time.In this paper,intelligent colorimetric film was prepared with biodegradable polymer as matrix and purple cabbage anthocyanin as pH response dye,which was used to detect the freshness of pork and shrimp.The primary research work and results included the following parts:(1)Anthocyanins extracted from purple cabbage through solvent method.According to the experimental results of single factor extraction,the main influencing factors were selected for orthogonal experiment.Through the analysis of range and variance of the results of orthogonal experiment,we got the optimal extraction parameters that the extraction temperature and time was 50?and 30 min respectively,and the extraction agent was acetic acid/60%ethanol aqueous solution(pH=2.8-3.0).Then,it was found that the maximum absorption peak,absorbance and color of purple cabbage anthocyanins in buffer solution with different pH values would change,which laid the foundation for its application in the detection of food freshness.(2)Study on preparation and properties of colorimetric films with different substrates.Polyvinyl alcohol/chitosan film(CP),polyvinyl alcohol/starch film(SP),polyvinyl alcohol/carboxymethylcellulose sodium film(CMP),polyvinyl alcohol/chitosan film/purple cabbage anthocyanin film(CPA),polyvinyl alcohol/starch/purple cabbage anthocyanin film(SPA),polyvinyl alcohol/carboxymethyl cellulose sodium/purple cabbage anthocyanin film(CMPA)were prepared by using polyvinyl alcohol,chitosan,starch,and sodium carboxymethyl cellulose as film-forming substrates and incorporated with purple cabbage anthocyanin respectively.Through the characterization of the appearance color,physical properties,intelligent indication effect,microstructure and infrared spectrum of the intelligent colorimetric films,it is found that the color response of CMPA film in different pH solution and ammonia gas was the most sensitive and the color stability is good,while the difference of mechanical properties could be improved by adding plasticizer.Hence,CMPA film was selected to detect the freshness of pork and shrimp.(3)Study on the determination of freshness of pork and shrimp by using colorimetric film.CMPA-20,CMPA-40 and CMPA-60 colorimetric films were prepared by using polyvinyl alcohol/sodium carboxymethyl cellulose as film-forming matrix and adding different amounts of purple cabbage anthocyanins.Different colorimetric films were applied to detect the freshness of pork and shrimp.The freshness detection effect of pork and shrimp was evaluated by measuring the relationship between TVB-N value,pH value and color change of colorimetric film within 24 hours.The results showed that CMPA films with different contents of anthocyanin in purple cabbage showed obvious color changes during the freshness detection of pork and shrimp.Meanwhile,through analyzing the correlation between the color difference?E~*of each colorimetric film in freshness detection and the TVB-N value of pork and shrimp,it is found that the color change of CMPA-20 colorimetric film has a good correlation with TVB-N value,and the color response is more obvious.(4)Study on the kinetics of colorimetric film and pork quality.The dynamic modeling and analysis were carried out by taking the TVB-N value of pork as the quality factor and the color difference of colorimetric film as the response parameter in the application of pork freshness detection.Through the analysis and calculation of Arrhenius equation,the activation energy of pork and colorimetric film are 66.34 kJ/mol and 55.31kJ/mol,respectively.Since the activation energy difference between the two was less than 25 kJ/mol and the change time of color difference is close to the shelf life of pork,the colorimetric film can be used for the detection of pork freshness.