Preparation Of Lipophilic SiO₂/LLDPE Composite Membrane And Its Application In Preservation Of Sweet Corn

Nanoparticles have many special physical and chemical properties because of their unique structure.Nowadays,there are many types of nanoparticles being widely used in the various of fields.Great achievement of nano silica(SiO2)had been got in its preparation,modification and application,so it had a wide application foreground.However,it was not mature to prepare a composite film used for the preservation of fruits and vegetables.In this paper,nano SiO2 modified by silane coupling agent was doped into linear low density polyethylene(LLDPE)to prepare lipophilic SiO2/LLDPE composite membrane.The composite film was studied at 5 degrees Celsius to investigate its effect on storage quality of sweet corn.This invention was intended to be applied to the preservation of this kind of fruit which needed to be stored in the environment of hypoxic hypercapnic.The main results of this p.aper are as follows:1)The preparation of lipophilic SiO2/LLDPE composite membrane and determination of the optimum nano SiO2 content in the composite membrane Two different silane coupling agents KH-560 and KH-570 were used to modificate nano SiO2 respectively.Different content of modified SiO2 was added into LLDPE matrix by hot pressing procedure to got lipophilic SiO2/LLDPE composite membrane.Scanning electron microscopy showed that nano SiO2 evenly dispersed in LLDPE and there was no obvious reunion phenomenon.In this paper,masterbatch was prepared by adding nano SiO2 and LLDPE in mixer,and then the masterbatch was put into flat-bed press to achieve nano SiO2/LLDPE composite film.The contents of SiO2 were 0.5%,1.0%,1.5%and 2.0%respectly.The mechanical properties,water vapor transmission rate,permeability and the transmittance was studied to evaluate the performance of the composite membrane.Comprehensive comparison showed that when the modified nano SiO2 content was 1.0%,the overall performance of the composite film was the best.Compared with the pure LLDPE film,the maximum tensile strength and elongation at break increased by 36.76%and 24.48%respectively,The transmittance of O2 and the transmissivity of CO2 and water vapor transmission decreased by 26.8%,10.5%and 16.33%respectively.2)the fresh-keeping effect of lipophilic SiO2/LLDPE composite membrane on sweet cornAs pure LLDPE film was used as the control group to study the effects of the lipophilic SiO2/LLDPE composite membrane on the storage quality of sweet corn at 5 degrees Celsius.It showed that:compared with the pure LLDPE membrane,lipophilic SiO2/LLDPE composite membrane for sweet corn preservation played a more active role in the specific performance:the decay index,reduce the weight loss rate of fresh sweet corn,firmness,respiration and ethanol content,compared with the pure LLDPE film,the above indexes maximum reduction was 20.15%,34.28%,23.53%,17.81%and 51.35%respectively,and the composite film maintained TSS content,Vc content,sugar content and soluble sugar content,compared with the pure LLDPE membrane,the above indexes maximum reduction was 25.31%,33.33%,8.12%and 25.80%respectively,the soluble protein content did not change significantly.The film delayed the time which intensity and the starch content reached the peak time,prolonged the retention period of sweet corn.Therefore,the lipophilic SiO2/LLDPE composite membrane played a good role in the storage of sweet corn,and it has potential market prospect as a kind of sweet corn preservation material.