Preparation And Application Of Active Composite Films Based On Loquat Kernel Starch/resveratrol

Starch is widely used as a film-forming substrate for biodegradable films due to its natural abundance,low cost,easy availability,renewability and good film-forming ability.Loquat seed is a by-product produced after fresh eating or processing,containing abundant starch（amylose）,which can be used as a new unconventional starch source for preparing starch films.However,pure starch films have problems such as poor mechanical properties,barrier properties and single function,limiting their practical application in the packaging field.Therefore,developing starch-based food packaging materials with good comprehensive performance and antioxidant/antibacterial activity has become a current research hotspot.Based on this,this experiment proposes to use loquat seed starch（LSS）extracted by ultrasonic assisted enzyme extraction as the starch matrix for film formation,and resveratrol-loaded zein/pectin core-shell nanoparticles（En-RES）prepared by antisolvent method as antioxidant additives,to prepare LSS/En-RES degradable antioxidant packaging films with excellent comprehensive performance by solution casting method,and apply them to the storage experiment of soybean oil to explore their potential in antioxidant packaging.The main research content and results are as follows:（1）In this study,ultrasound-assisted enzymatic extraction method was used to extract loquat seed starch.The effects of ultrasound power,ultrasound time,enzymatic hydrolysis time,and enzyme addition on the extraction rate were investigated.The extraction process was optimized by response surface experiments,and the extracted starch was characterized.The results showed that the highest extraction rate of loquat seed starch（47.76%）was achieved when the ultrasound power was 2.50 W/g,the ultrasound time was 42.00 min,the enzymatic hydrolysis time was 8.10 h,and the enzyme addition was 1.00%.The extracted starch had high purity（88.29%）,with a high percentage of amylose（23.86%）.Its morphology was mainly elliptical,with a particle size of about 9.99μm,which is a typical type C starch.The starch had low gelatinization viscosity and breakdown value,indicating excellent film-forming properties.（2）In order to endow the starch film with antioxidant activity,the experiment used anti-solvent method to prepare resveratrol-loaded core-shell nanoparticle（En-RES）and added them into LSS-based films to investigate the effect of En-RES content（0～20%）on the structure and properties of the composite films.The results showed that En-RES dispersed well in the matrix,and there was a good hydrogen bonding interaction between En-RES and starch.When the En-RES mass fraction was 15%,the LSS/En-RES composite film had excellent comprehensive properties.Its tensile strength was 9.17 MPa,and elongation at break was 36.22%.In addition,the oxygen barrier property of the composite film was 0.62×10^-14 kg·m·m^-2·s^-1·Pa^-1,and the antioxidant activity reached 68.01%.This indicated that the film had good barrier properties and antioxidant activity.The release of encapsulated resveratrol is slower,and the stable release period reaches more than 14 days,which can achieve the effect of controlled release,indicating that it has certain potential in the application of antioxidant packaging in food.（3）The application effect of LSS/En-RES composite films in degradable antioxidant packaging was further evaluated by accelerated oxidation test,heat seal test and soil degradation test of soybean oil.This experiment investigates the changes in odor,transparency,acid value,saponification value,anisidine value,and other indicators of soybean oil under accelerated oxidation conditions（50℃;50%RH）,and the results show that the total oxidation value of soybean oil in the LSS/En-RES composite film is 168.47after 30 days of storage,which is significantly lower than the blank control group（212.39）,indicating that the LSS/En-RES composite film can delay the lipid oxidation of soybean oil.In order to further verify the practical application potential of composite film in fatty food,this experiment optimized the heat sealing process through orthogonal experiment to obtain good heat sealing effect,and the heat sealing strength was up to 7.48N/15mm.The composite film was used to seal soybean oil into bags,and the sealed bags had good sealing performance without any leakage,indicating that the film has good resistance to oil penetration.After 18 days of storage,the peroxide value and acid value of the LSS/En-RES composite film group were significantly lower than those of the blank control group,indicating that the LSS/En-RES composite film has strong practical value in oil food.