Preparation Of UV Barrier Film Material With Antioxidant Activity And Its Application In Sunflower Oil Preservation

Some organic substances in food are susceptible to photo-oxidative degradation under the influence of ultraviolet light,which leads to the decline of sensory characteristics.The oxidative rancidity forms of oil include free radical chain automatic oxidation,photosensitive oxidation and enzymatic oxidation,and the resulting adverse effects include:deterioration of oil flavor,loss of nutrition,deterioration of sensory properties and production of toxic substances.Therefore,this topic mainly studied a kind of UV barrier film material with antioxidant activity,and characterized and tested its physical and chemical properties,and put it into the fresh-keeping use of oil.First,a composite film with ultraviolet barrier properties was prepared by adding different proportions of nano-silica（Nano-Si O₂）and lignin to the hydroxypropyl methylcellulose（HPMC）/polyvinyl alcohol（PVA）film matrix.Comparing the performance characteristics of each group of films,a composite film with the best comprehensive performance was selected,and then 2.5%gallic acid（GA）,tea tree oil（TTO）,tea polyphenols（Tea polyphenols,TP）were added to the composite film matrix to obtain three different properties UV barrier film with antioxidant activity,the physical and chemical properties of the film was tested and analyzed.Using polypropylene（PP）as the outer packaging material and the active film as the inner packaging material,the sunflower oil was bagged and packaged for 5 weeks,and the degree of oxidative rancidity of the oil sample was tested and analyzed.The conclusions of this study are as follows:1.The inorganic substance Nano-SiO₂ can be more uniformly dispersed in the film matrix,and the addition of a small amount of Nano-Si O₂ can improve the oxygen resistance and tensile strength of the film,while reducing the transmittance of ultraviolet light When the Nano-Si O₂ content increases,agglomeration occurred in the film matrix,and the barrier properties of the composite film became worse and the tensile strength decreased.The heat resistance of the film decreased after the addition of lignin;the toughness and ultraviolet barrier of the film were positively correlated with the content of lignin;and the elongation at break of the three composite films containing 1.2%lignin was greater than that 180%is 2.5 times that of PVA（0.6%HPMC）film（73.14%）,simultaneous film T_UVA<10%and T_UVB tends to 0.No.4composite film with 0.4%Nano-Si O₂,1.2%lignin had high ultraviolet barrier ability and barrier ability,excellent mechanical properties,the best comprehensive performance.2.Three antioxidant active films containing GA,TP and TTO exhibited better UV barrier function and tensile properties:T₃₁₅<0.9%,T₃₄₀<3.2%。The O₂transmittance of 2.5%GA and 2.5%TP,which contain hydrophilic plant polyphenols,was 0.1535 cc·（m²·day）^-1、0.1508 cc（m²·day）^-1,compared with KB group films to obtain better oxygen barrier performance.The lipophilicity of the film was:2.5%GA<2.5%TP<KB<2.5%TTO。The results of the antioxidant experiment showed that the 2.5%GA film had very good oxidation resistance,the clearance of DPPH free radicals was as high as 93.5%,and the iron reducing force was 24 of the KB film multiplied.The oxidation resistance of the film was:2.5%GA>2.5%TP>2.5%TTO>KB.3.When studying the release law of the active film,it was found that the three active substances had a good release effect in the lipid simulation solution of 95%alcohol.During the short-term release process at 3 h,the release behavior of the active substance in the lipid food simulation solution basically conformed to the zero-level model（R²>0.9）.The results of the release kinetic model fitting within 144h showed that for 2.5%GA,2.5%TP active film primary model fitting accuracy was higher,and R² was 0.9787 and 0.9854 respectively.For 2.5%TTO film,Weibull model had a higher fitting degree,R²=0.9251.4.In the light preservation experiment,the content of moisture and volatile substances in each group of oil samples changed very little,and the final result did not exceed 0.045%.Through the detection of primary oxidation products and secondary oxidation products,it was found that each group of oil samples in the storage process has oxidative rancidity to varying degrees,resulting in a small number of small molecular substances such as aldehydes and ketones.During the 5-week experiment,the peroxide value of the oil samples in the GA2.5%group only increased from2.94mmol/Kg to 6.43mmol/Kg,an increase of about 1.19 times;the a cid price increased from 0.2133 mg KOH/g increased to 0.3567 mg KOH/g,an increase of about 0.67 times;The conjugated diene value increased from 0.64 to 1.73,the conjugated triene value increased from 0.58 to 1.80,and the thiobarbiturate acid value increased the least.Combining various indicators,GA2.5%film had the best preservation effect on sunflower oil,and the protective properties of the film against oil and fat are 2.5%GA>2.5%TP>2.5%TTO>KB,which was the same as the strength and weakness of the film’s in vitro antioxidant properties.According to the experimental results,the UV barrier film material with antioxidant activity in this study had a significant slowing effect on the oxidative rancidity of oils and fats,and the material had a promising application in lipid food.