| The intelligent indicator package of freshness has the advantages of real-time,convenient,efficient and low-cost.It is often applied to the quality control of fresh food in the processes of storage,transportation and sale.At the same time,the monitoring process will not cause damage to the appearance of food,so that consumers can directly read the freshness quality status of fresh food from the food package,which greatly increases consumers’confidence in eating sub-fresh food and reduces food waste.Flammulina velutipes is rich in nutrition and fresh taste,which is favored by consumers at home and abroad.However,it still maintains a high level of physiological metabolism after harvest,resulting in a rapid reduction of freshness quality and making it difficult to store for a long time.The freshness indicator film can monitor the freshness quality changes of Flammulina velutipes during storage in real time so that consumers can quickly distinguish the freshness quality of Flammulina velutipes during storage.The purpose of this study was to develop an intelligent indicator film of starch-based packaging material loaded with purple sweet potato anthocyanins for monitoring the freshness of Flammulina velutipes during storage.The main contents and conclusions of this study are as follows:Extraction conditions of anthocyanins from purple sweet potato and determination of their content and species composition.The effects of different solid-liquid ratios,extraction temperatures,and extraction times on anthocyanin extraction rate from purple sweet potato were investigated.The response surface method was used to obtain the optimal extraction conditions of purple sweet potato anthocyanins based on the analysis of single factor experiment results:solid-liquid ratio of 1:45,extraction temperature of 50°C,extraction time of 25min,and finally the extraction rate of purple sweet potato anthocyanins was 139.17(mg/100g).In the analysis of anthocyanins types and contents,it was found that anthocyanins mainly contained cyanidin and peony pigment,and the highest content of three anthocyanins were respectively centaurin-3-(6"-caffeoyl sophoroside)-5-glucoside(31.62%),peoniflorin-3-O-P-hydroxybenzoyl sophoroside-5-glucoside(25.83%)and peoniflorin-3-sophoroside-5-glucoside(17.92%).p H sensitivity analysis of anthocyanin extracts from Purple sweet potato and preparation of blending membrane of starch/gelatin/Purple sweet potato anthocyanin extracts.The results showed that anthocyanins of purple sweet potato had a sensitive response to environmental p H changes.Compared with the pure starch film,the starch and gelatin 1:1 blend film has a lower water content and better water vapor blocking ability,and the mechanical strength has been significantly enhanced.In addition,the addition of anthocyanin extracts of purple sweet potato made the starch/gelatin blend film have better UV blocking ability and strong p H sensitivity.In the process of investigating the stability of starch/gelatin based intelligent film,it was found that the stability of intelligent indicator film is better at 4°C and 10°C,and the stability at 20°C is the worst,which limits the application range of blend film to a certain extent.Identification of fresh quality of Flammulina velutipes by blending film of starch/gelatin/purple sweet potato anthocyanin extract.The results showed that the freshness quality of Flammulina velutipes decreased and the content of carbon dioxide in the packaging increased during storage at 4°C.At the same time,the content of carbon dioxide in the package was significantly correlated with the quality parameters of the fresh degree of Flammulina velutipes and the color difference value of the intelligent indicator film.The degree of freshness of Flammulina velutipes during storage can be determined by observing color changes in the blending film.Based on the principal component analysis of the quality parameters of the freshness and the color parameters of the blending film during the storage of Flammulina velutipes,it is concluded that the blending film can qualitatively predict the freshness of Flammulina velutipes during the storage.Together with the freshness quality parameters of Flammulina velutipes during storage,the color parameters of the blend film were used as independent variables to build a partial least squares regression model.This model was used to predict the freshness index parameters during storage in a quantitative way.Moreover,the prediction ability was evaluated,including the residual prediction deviation(RPD>2)of the constructed model.The quantitative prediction results of the model were reliable for the relative electrical conductivity(Rc~2=0.949),Browning index(Rc~2=0.932)and sensory evaluation score(Rc~2=0.943)during the storage of Flammulina velutipes.In order to meet the requirements of real-time,non-destructive,safe and convenient monitoring of the quality changes of Flammulina velutipes during storage,the blend film prepared in this study can show different colors according to the freshness of Flammulina velutipes during storage,so as to achieve real-time monitoring of the freshness of Flammulina velutipes. |
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