Preparation And Application Of Edible Film Based On Pectin/Sodium Alginate/Xanthan Gum

In recent years,with the upsurge of the"plastic limit order",edible polymer films and coatings used to preserve food have attracted much attention.At the same time,with the increasing demand of consumers for natural and safe food,edible packaging came into being.Nowadays,some color-sensitive natural compounds are added into the innovation of food packaging,which makes it an active intelligent packaging and can monitor the freshness of packaged food.In this paper,three edible anionic polysaccharides,pectin,sodium alginate and xanthan gum,were selected to prepare composite film liquid and composite film(PAX),and their comprehensive properties were studied and applied to the packaging of fresh-cut potatoes.Then,the red raspberry pomace extract(RPE)with anthocyanin as the main component was loaded on the composite membrane to study its influence on PAX,and it was applied to monitor pork freshness.The main research contents and results are as follows:(1)The effects of the concentration of film matrix and the temperature on the rheological properties of the PAX film system were studied by rheometer.The results showed that PAX film liquid had shear thinning characteristics,and the rheological properties conform to the power law equation of Ostwald de Waele,With the increase of pectin,sodium alginate and xanthan gum concentration and the decrease of test temperature,the viscosity of composite film solutions increased,and the non-Newtonian characteristics became more obvious.With the increase of pectin,sodium alginate and xanthan gum concentration,the intersection of G'and G'gradually appeared and moved to low frequency.According to the rheological characteristics and practical properties,the optimum concentration of pectin,sodium alginate and xanthan gum was determined to be 0.6%,0.5%and 0.4%,respectively.(2)The effects of xanthan gum concentration,glycerol concentration and Ca Cl₂concentration on the tensile strength of composite film were investigated by single factor test.Based on this,the optimum conditions for preparing composite film were obtained by response surface methodology.Considering the convenience and feasibility of practical operation,0.4%xanthan gum,1.8%glycerol and 2%Ca Cl₂were selected for further index determination.The tensile strength of the composite film was 29.65 Mpa,the water vapor transmission rate was 18.12×10^-11g/(m²·s·Pa),the elongation at break was 19.02%,the opacity was 0.217,and the ABTS clearance rate was 30.Scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)showed that the composite film had smooth and uniform surface,strong intermolecular force and good compatibility,which provided a new way for the preparation of new natural polysaccharide film.(3)The effects of PAX packaging film,PAX coating and PAX coating+Ca Cl₂on the quality of fresh-cut potatoes were compared at-4?.The results showed that the preservation effect of PAX coating was not much different from that of PAX coating+Ca Cl₂,but both of them were obviously better than that of PAX,which could effectively reduce the weight loss rate,browning degree,malondialdehyde content,polyphenol oxidase and peroxidase activity of fresh-cut potatoes and maintain the sensory quality of fresh-cut potatoes.(4)With the increase of RPE concentration,the thickness and density of raspberry film gradually decreased.Tensile strength of PAXR₃₀increased significantly from 29.65 MPa to39.81 MPa,elongation at break decreased gradually from 19.02%to 13.11%,moisture permeability decreased with the increase of RPE,opacity and ultraviolet barrier performance increased,ABTS clearance increased gradually from 35.31%to 95.86%of PAXR₃₀,and antioxidant capacity was greatly enhanced.SEM,FTIR and thermogravimetric analysis proved that RPE and PAX had good compatibility,and RPE enhanced the thermal stability of PAX.This study provided relevant theoretical data for the preparation of raspberry film.(5)Anthocyanins showed different colors under different p H conditions,the sensory evaluation of pork stored at 25?was carried out at different time points.The p H value,lipid peroxidation and total number of colonies were tested,and the color change of PAXR₁₅placed on the surface of pork was tracked and observed,which proved that PAXR₁₅can sensitively sense the freshness of pork with pork spoilage,and is expected to provide a promising and rapid nondestructive detection method for the freshness of protein-rich food.