| The objective of this study was the extraction technology of papain on collagen protein from silver carp scale,the process of silver carp scale collagen and chitosan blend film,the process of collagen-chitosan composite membrane modified by tea polyphenol and the preparation of these two kinds of composite membrane,so as to improve the utilization value of the silver carp leftovers and develop the new kind of edible preservation film.The Hypophthalmichthys molitrix scale collagen was extracted by papain and the preparation technology was optimized by single factor experiment and orthogonal experiment.The extraction time,solid-liquid ratio and enzyme concentration of papain were studied.The results showed that the optimum conditions were as follows:enzyme concentration was 4%,extraction time was 36 h,solid-liquid ratio was 1:25,and extraction rate was 17.48%.The thermal denaturation temperature of the collagen was 29?,which is significantly lower than the thermal denaturation temperature of terrestrial collagen.Research on water absorption and water retention found that silver carp scales collagen has good water absorption,and water retention was better than glycerol,which can be applied to food and other related industries.Automated amino acid analysis showed that glycine and hydroxyprolinecontent was higher in collagen,while cystine,isoleucine and tyrosine was lower,consistent with type?collagen.The composite membrane of silver carp collagen and chitosan were prepared and the collagen-chitosan composite membrane was modified by tea polyphenols.The physical and chemical properties of the two composite membranes were also analyzed.The best proportion of collagen-chitosan blend film was 2% chitosan,2% collagen,the ratio of collagen and chitosan was 1: 4,the amount of glycerol was 25%.The collagen film has the highest tensile strength,the highest light transmittance,and the lowest water vapor transmission rate.The morphology and structure of the collagen-chitosan composite membrane under the conditions of scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)showed that the good compatibility between collagen and chitosan.The optimum preparation of collagen-chitosan composite film modified by tea polyphenols were as follows:the content of tea polyphenols was 0.5%,the concentration of collagen was 6%,the ratio of collagen and chitosan was 1: 4.And the mechanical properties,light transmittance and water vapor transmission rate were significantly improved compared with the collagen-chitosan composite membrane.SEM and FTIR analysis showed that the morphology of the composite membrane was changed for the tea polyphenols,and the characteristic peaks of the infrared spectra showed much shift,which indicated that the tea polyphenols,collagen and chitosan has strong compatibility.The preservation effects of collagen-chitosan blend film modified by tea polyphenols on the quality of Eponepheluscoioides were evaluated,Samples of the blank control group(T0),collagen-chitosan blend film(T1)and blend film modified by tea polyphenols(T2)were stored at 4? for 20 days,the K values,actomyosin content,total sulfhydryl content(-SH),Ca2+-ATPase activity,pH,total volatile basic nitrogen(TVB-N)value,thiobarbityric acid(TBA)value,total viable counts(TVC),sensory evaluation were measured.The results indicated that total sulfhydryl content,actomyosin content,Ca2+-ATPase activity and and sensory evaluation of T1 and T2 were significantly(P<0.05)higher than T0,while the K values,pH,TVB-N,TVC were significantly(P<0.05)lower than T0,and the preservation effect of T2 were more effective than T1.Furthermore,the difference of TBA was not significant(P?0.05)in these three groups.With the treatment of T2,actomyosin was degenerated slowly,the reduction of-SH content and Ca2+-ATPase activity was hampered,the increase of TVB-N and TVC were also inhibited.This observation suggested that in the 4? refrigerated condition,the blend film modified by tea polyphenols could effectively retard spoilage of Epinepheluscoioides,which has more advantage in preservation. |
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