Research On Preparation And Preservation Performance Of Nanoparticle Modified LDPE Film

Nanoparticle usually has unique physical and chemical characteristics and has become attractive to researchers in recent years. Nano-TiO2and nano-SiO2are two kinds of nano metallic oxide which have been researched in some academic fields. Nanoparticle composite material has revealed its importance in agricultural products preservation these years. In this study, nano-TiO2modified low density polyethylene (LDPE) film packaging and nano-SiO2modified LDPE film packaging were prepared by blending LDPE with nano-TiO2and nano-SiO2, respectively. The effects of both nanoparticle modified LDPE film packaging on quality of strawberry and Penaeus Vannmei were investigated. The main results were as follows:1) Preparation of nanoparticle modified LDPE film and determination of the dosageNano-TiO2and nano-SiO2were modified by titanate coupling agent before blending with LDPE, respectively. Transmission electron microscopy showed that nanoparticles were well-distributed in LDPE and still reached nano-scale. Nano-TiO2LDPE film and nano-SiO2LDPE film with different nanoparticle dosage were prepared by single screw extruder. The kind and the dosage of nanoparticle were considered to have influence on the mechanical properties, air transmission, water vapor transmission and ultra-violet and visible light transmission of films after measurement. Nano-TiO2LDPE film with1%nano-TiO2addition and nano-SiO2LDPE film with0.5%nano-SiO2addition were considered the best dosage after comprehensive comparison and were used as the packaging materials in later study on preservation. Compared with normal LDPE film, the tensile strength of nano-TiO2LDPE film and nano-SiO2LDPE film were increased by45.42%and32.63%, elongation at break were increased by13.17%and10.48%, air transmission were reduced by32.94%and23.35%and water vapor transmission were reduced by4.48%and3.98%, respectively.2) Effect of nanoparticle modified LDPE film on quality of postharvest strawberryThe effect of nanoparticle modified LDPE films on physiology and quality of postharvest strawberry storing under4℃were investigated. Results showed that compared with the control (normal LDPE film), nano-TiO2LDPE film packaging and nano-SiO2LDPE film packaging were more effective on reducing decay rate, weight loss and ethylene production and could also inhibite the reduction of firmness and titratable acid content. Additionally, nano-TiO2LDPE packaging and nano-SiO2LDPE packaging could keep ascorbic acid and total phenols contents, as well as antioxidant ability, at relatively higher level during the later storage period. Meanwhile, suppressed reactive oxygen species (ROS) accumulations including superoxide anion and hydrogen peroxide were lower than the control and the activities of antioxidant enzymes involved in ROS scavenging action were significantly higher than the control at the later period of storage. Compared with the control, nano-TiO2LDPE packaging and nano-SiO2LDPE packaging inhibited decay rate by60.72%and42.85%, inhibited ethylene production by40.32%and21.47%at the end of storage, respectively. And the firmness values were24.35%and20.07%higher; the ascorbic acid contents were29.22%and19.09%higher, respectively. These results indicated that nano-TiO2LDPE film packaging and nano-SiO2LDPE film packaging were both effective on maintaining quality and prolonging storage life of strawberry.3) Effect of nanoparticle modified LDPE film on quality of Penaeus VannmeiThe effect of nanoparticle modified LDPE films on quality of Penaeus Vannmei storing under4℃were investigated. Results showed that compared with the control (normal LDPE film), nano-TiO2LDPE film packaging and nano-SiO2LDPE film packaging were more effective on inhibiting deterioration of sensory quality and texture properties. Both of the nanoparticle modified LDPE films retarded the decrease of whiteness and water holding capacity and the increase of pH value, K value and melanosis score. Additionally, they could keep TVB-N content and TBARS value, as well as PPO activity and total viable counts (TVC), at relatively lower level during storage. Compared with the control, nano-TiO2LDPE packaging and nano-SiO2LDPE packaging increased sensory score by30.77%and26.92%while reduced TVC by6.42%and4.38%at the end of storage, respectively. And the K values were28.50%and22.22%lower; TVB-N contents were14.82%and8.09% lower, respectively. These results indicated that both kinds of nanoparticle LDPE film packaging had great effects on extending shelf life of Penaeus Vannmei.