Preparation Of Cross-linked Modified Guar Gum-based Film And Its Application In Quality Control Of Postharvest Agaricus Bisporus

Guar gum is an environmentally friendly natural polymer material with a wide range of sources,and it is easy to obtain and relatively low cost.It can be used as a substrate for new biodegradable composite films.However,high viscosity gelled structure of guar gum at low concentration is formed,which affects its film-forming property;At the same time,the overall properties of the guar gum film,such as mechanical strength,light transmittance,and barrier properties,need to be improved.In this paper,guar gum was used as the film substrate,and a modifier(3-chloropropyl)triethoxysilane was added to modify it.By adjusting the p H of the film liquid,its high viscosity characteristics were improved to facilitate film formation,and a modified guar gum film was prepared.The modified guar gum/whey protein composite film was prepared by selecting the film liquid ratio of the modified guar gum film with good performance,supplemented by different mass fractions of whey protein for composite crosslinking to further improve the overall performance of the film.The antioxidant active substance rutin was added to the composite film and the film was applied to the preservation experiment of Agaricus bisporus.The results of the study were as follows:(1)A modified guar gum film was prepared using guar gum as the substrate and adding(3-chloropropyl)triethoxysilane to modify it.The modified film was characterized by Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),Xray diffraction(XRD),differential scanning calorimetry(DSC),and rheological analysis.The mechanical and barrier properties of the film were measured and analyzed.FTIR images showed that compared to a single guar gum film,the strength of the film added with the modifier shifted slightly and decreased near the hydroxyl absorption band,indicating that the hydroxyl group in the guar gum had been replaced by the methyl group in the modifier.The SEM and XRD images of the modified film show that different concentrations of modifiers can affect their distribution within the film substrate,and hydrogen bonds and siloxane bridges are formed between them DSC results showed that the thermal properties of the modified film were improved,indicating that the addition of modifiers effectively enhanced the intermolecular bonding of guar gum.In terms of mechanical properties and barrier properties,the modified film has the best performance.Compared to the tensile strength(TS)of pure guar gum(16.58 MPa),the tensile strength was the best(27.39 MPa).when the amount of modifier added is 30%.Through rheological analysis,it was found that adjusting the p H of the modified guar gum aqueous solution is beneficial to its film formation.As the p H value increases,the viscosity of the film liquid presents a downward trend.When the p H is 8,the film liquid exhibits a casting characteristic that is conducive to film formation,and it is considered as the final choice.(2)By preparing modified guar gum/whey protein composite films with different ratios,it was found that when the ratio of guar gum to whey protein was 1:0.6(G’/W-2),the mechanical properties of the composite film were the best.At this time,the TS of the film was 39.92 MPa,and the elongation at break(EAB)was 31.13%.The combination of them can effectively compensate for the defects of the monomer film.In addition,through SEM,XRD,and FTIR images,it was found that the compatibility between them was good,and the surface of the composite film was smooth and transparent.After adding rutin,the active film(G’/W-R)has good UV barrier performance,and when applying it to packaging fruits for preservation,it can also effectively protect food from oxidation and UV light damage.Studies on the preservation of Agaricus bisporus showed that the G’/W-R group treatment can effectively delay the browning of Agaricus bisporus,reduce respiratory rate,and maintain high hardness.Additionally,this treatment can also effectively prevent the decline in weight loss rate.(3)Meanwhile,the antioxidant effect of modified guar gum/whey protein/rutin composite film(G’/W-R)during the preservation of Agaricus bisporus was studied.The results showed that compared with the control group and the G’/W-2 group,the treatment of G’/W-R group could effectively inhibit the decrease of malondialdehyde(MDA)content and maintain the integrity and stability of the cell film;It also could effectively remove active oxygen species(ROS)and reduce the its accumulation,further terminate the free radical chain reaction and maintain a high content of total phenols and flavonoids.At the same time,it can activate the ascorbic acid glutathione(As A-GSH)circulation system in Agaricus bisporus storage,increase the content of ascorbic acid(As A)and glutathione(GSH),promote peroxidase(POD),superoxide dismutase(SOD),catalase(CAT),ascorbic acid peroxidase(APX)and glutathione reductase(GR)The activities of monohydroascorbic acid reductase(MDHAR)and dehydroascorbic acid reductase(DHAR)were relatively higher and excess ROS was effectively removed during the preservation process of Agaricus bisporus,so the aging process was thus delayed.