Preparation And Exploration Of Intelligent Indication Packaging Film For Anthocyanin-based Pork Freshness

Food freshness is one of the important indexes for consumers to judge food quality and safety.Intelligent packaging can provide consumers with more convenient and more reliable food safety protection,in which freshness indication packaging film can judge the freshness and edible value of food by sensing the changes of features in the environment.Using the principle that anthocyanin color is affected by pH,it can be used to monitor environmental changes inside meat packaging and to detect food freshness.However,the color rendering of anthocyanins in practice is affected by many factors,including source,temperature,matrix,and environment.In this study,anthocyanins are extracted from natural plant materials,starch and chitosan are used as matrix materials,and glycerol is used as a plasticizer.The main research contents are as follows:(1)The properties of anthocyanins from different sources are investigated:Anthocyanins are extracted from black beans,black rice,black lycium barbarum,and mulberry raw materials.All kinds of anthocyanins show good antioxidant properties,and the antioxidant properties of anthocyanin extracts from various sources:black lycium barbarum>black rice>mulberry>black bean.The variation of the color and stability of the four anthocyanins under pH=2-10 are investigated,the results show significant difference in coloration.The color gamut changes of black lycium barbarum anthocyanins are most easily recognized by naked eyes,and the corresponding color difference value is the largest,and the results show that in solution,when the environmental pH is acidic,the anthocyanins color is stable.(2)Preparation and properties of anthocyanin indicator packaging film are investigated:Chitosan and starch are used as the film matrix material,glycerol as the plasticizer,and anthocyanin extracts from different sources are added as functional substances.After adding anthocyanin extracts from different sources,the elongation at break of composite membrane decreased significantly,and the effect of low anthocyanin concentration is weaker than that of high anthocyanin concentration.Secondly,the antioxidant properties of the composite film are measured,and the results show that anthocyanin significantly increased the antioxidant properties of the composite film.Then,the stability of the film is investigated at 25℃,4℃,and-18℃ storage temperature.The results show that the stability of black beans and black rice anthocyanin indication packaging film is good.(3)Anthocyanin indicator packaging film is applied to pork freshness detection:Using composite film as pork packaging and storing at 25℃,4℃,and-18℃.Under storage conditions of-18℃,the pH value of pork samples remain unchanged,and the pH value of other groups of samples show an increasing trend with time.Secondly,the volatile basic nitrogen of the sample is measured at 4℃ storage temperature,and the results show that there is no significant difference between the four anthocyanin composite films.And the color change of the composite film used in pork samples with time is determined.The results show that the black lycium barbarum composite film has the best color rendering effect,the largest change,and the easiest identification.The experimental results show that the color development of the four anthocyanins in the solution and the composite film is significantly different.The anthocyanin composite film can be used for the detection of pork freshness,and the color of the anthocyanin from different sources for pork freshness detection is not exactly the same.From the perspective of color rendering effect and stability,the black lycium barbarum anthocyanins perform best.This research provides a reference for the packaging material of freshness intelligent indication.