Preparation Of Intelligent Indicator Film Based On Purple Sweet Potato Anthocyanin And Freshness Detect Application

Intelligent packaging based on natural anthocyanin is a novel packaging technology,which provides a real-time information on food quality for consumers.It have gradually attracted research interests,since they are safer and more ecofriendly.In the present work,purple sweet potato anthocyanins(PSPA)were used as the indicator.Indicator films were prepared through a recipe consists of starch(S),carboxymethyl cellulose(CMC)and konjac glucomannan(KGM).The film-forming substrate for indicator was selected,and the process parameters were optimized.The color stability and sensitivity of indicator films were discussed.Afterwards,the fish freshness was evaluated.The main work and conclusion are as follows:(1)Intelligent indicator films were prepared by using binary combinations of S,CMC,and KGM.The natural anthocyanins from purple sweet potato(Ipomoea batatas(L.)lam)were used as the indicator.The mechanical properties,moisture content,water content,microstructure,compatibility,and stability of the intelligent indicator film were determined and compared.The results showed that the starch/carboxymethyl cellulose/ purple sweet potato anthocyanins composite film(SCP film)had the highest tensile strength(15.39±1.15 MPa),the lowest water content(24.17±1.21%),and the best stability of color.The konjac glucomannan/carboxymethyl cellulose/ starch/purple sweet potato anthocyanins intelligent indicator film(KCP film)had the best elongation(44.79±1.43%).Scanning electron microscopy assay showed that the microstructure of film with different constitution varied greatly,of which the cross section of the SCP composite film was smooth and tight.(2)Preparations and properties of intelligent indicator films from purple sweet potato anthocyanins and carboxymethyl-cellulose/starch were described.The effects of ratio of S to CMC,anthocyanin concentration and glycerol concentration on the physical properties such as tensile strength(TS),elongation at break(EAB),water soluble(WS)and color(a)were investigated.The comprehensive score of indicator film performance was used as the response value,the process parameters were optimized by the response surface method,and the optimal indicator film was characterized.The results demonstrated that the optimum recipe of indicator films were ratio of S to CMC of 6:4,anthocyanin concentration of 0.5% and glycerol concentration of 0.6%.The score of indicator films were the best overall as high as63.8 under these optimal conditions,and the properties of indicator films showed tensile strength of(21.48±0.12)MPa,elongation at break of(28.88±0.08)%,water solublity of(19.24±0.21)% and color of(4.95±0.02).Results of FT-IR,XRD and SEM indicated that the cross section of the SCP film was smooth and good compatibility of the ingredients.(3)The color stability and sensitivity of Purple sweet Potato Anthocyanin intelligent indicator film were discussed.The ?E values of indicator films were lower than 5,suggesting the color change could not be detected by naked eyes within 20 days.Indicator films showed greater color stability at low temperature(4?,-20?),low humidity in darkness.The indicator film has significant color change with different pH(2.0-12.0),and the maximum ?E values of indicator films reached 15.98±0.95.And the indicator films responded sensitively to volatile amines,with the release of volatile basic gas,while the color of films were changed from red to green,finally to yellow.(4)Study on application of purple sweet potato anthocyanins intelligent indicator film in fish was conducted.The indicator films were used to monitor the fish freshness.The fish stored at 4? for 8 days was evaluated for pH,sensory evaluation,total bacterial count(TVC),total volatile basic nitrogen(TVB-N),and observe the color change of indicator film.According to the results of TVB-N measurement,the fish was fresh whose TVB-N value was 18.78 mg/100 g at the 5th day,and the film turned into light blue.After 6th day,TVB-N values were more than 20 mg/100 g,and TVC reached and then exceeded 7 lg CFU/g,and the blue color of indicator films indicated that grass carp had been spoiled.And simultaneously,a strongest relationship between the color change of indicator film and TVB-N changes of fish.Moreover,the model was built based on color feature(RGB,Lab,HSV)values of the films combined with K-nearest neighbors(KNN)pattern recognition.The results showed that the model could effectively discriminate the fish in different freshness,and highest recognition rate for test set 98.68%.