Preparation of PVA-sweet corncob polysaccharide nano-silver composite film and its application in strawberry preservation
A polyvinyl alcohol-silver nanoparticles(PVA-AgNPs)composite film was prepared via tape casting method using PVA and soluble starch as film-forming matrix,glycerol as plasticizer,and AgNPs,which were obtainedd from sweet corncob polysaccharide(SCP),as filler.The preparation process of PVA-AgNPs was optimized by single factor experiment and response surface experiment taking tensile strength as index.The PVA-AgNPs obtained was characterized by FTIR and SEM,and evaluated for its performance in strawberry preservation.The results showed that the PVA-AgNPs,prepared from 2.3 g PVA,2.0 g soluble starch,4.0 mL glycerol and 4.0 mg AgNPs,exhibited the highest tensile strength[(14.08±0.58)MPa]and elongation at break(223.10%±5.29%),larger water contact angle(50.04°±0.03°)and lower water solubility(61.87%±0.17%)as well as more stable water vapor transmission rate(2.0%～2.5%)than PVA film(25.72°±0.69°,69.44%±0.16%,0.8%～2.3%),respectively.Meanwhile,the PVA-AgNPs showed a 30-day degradation rate of 44.67%±2.51%in soil at room temperature.PVA-AgNPs used as a packaging material for strawberries reduced the weight loss rate,spoilage rate,the loss of hardness,soluble solid content and VC content of strawberries,and stabilized the pH of strawberry.PVA-AgNPs was rough with slight folds in surface,while had pores and cracks inside.AgNPs enhanced the hydrophobicity of the composite film by covering the hydrophilic groups on the surface of PVA,and reduced the solubility of PVA-AgNPs in water by changing the water vapor transmission path.Through the absorption of visible light,the color of the composite film was deepened and its light transmittibility was reduced.The addition of AgNPs improved the barrier property of PVA-AgNPs to visible light,water and oxygen,and achieved the preservation of strawberry.
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