Preparation Of Polyvinyl Alcohol (PVA)-based Composite Film And Its Effect On Preservation Of Eggs

The eggs stored under the ambient temperature not only have a large number of microorganisms on the surface of the egg shell,but also can not meet the requirements of the merchants and the consumers on account of the nutritional quality is greatly reduced.Therefore,it is necessary to find a simple and convenient fresh-keeping method for fresh eggs.In recent years,polyvinyl alcohol film-coated preservation has attracted many researchers’ attention as a new type of packaging and preservation of eggs.It is a kind of relatively safe macromolecule material,but its water resistance performance is poor.It is often unable to obtain the ideal effect in the egg preservation.In order to improve the water resistance of polyvinyl alcohol(PVA)and improve its effect on the preservation of eggs,the following studies were carried out in this paper:1.Preparation and process optimization of PVA-based composite membrane materialIn order to improve the water resistance of PVA film,it was modified by nano-SiO2 and citral in this study.The water vapor transmittance of the membrane material was the response value with the addition of nano-SiO2 and citral as the independent variable.When 0.62 g/100mL nano-SiO2 and 3.93 mL/100mL citral were added in 5%PVA,respectively,the water vapor transmittance of the membrane was the lowest(768.73±20.51g/(m2·24h))by response surface method.In order to further improve the water resistance of membrane materials,polyvinylidene chloride(PVDC),with good water resistance was doped to PVA.It was found that when the content of PVDC was 6%,the water vapor transmittance of the blend film was the lowest.It was 612,86±12.19 g/(m2·24 h),which was 35.2%lower than that of virgin PVA film.The swelling ratio of the blend membrane was 161.13±1.62%,which was 24.0%lower than that of 5%virgin PVA membrane.2.Determination of properties and structural characterization of PVA-based composite membrane materialsPVA membranes,PVA-SiO2-citral composite membranes and blend membranes were prepared by casting method using the optimal preparation scheme of composite membrane materials.The properties(mechanical properties and water contact angle)and structure characterization(Scanning electron microscope,Fourier transform infrared spectroscopy and X-ray diffraction analysis)of the three kinds of membrane materials were measured.The results showed that compared with virgin PVA film,the tensile strength of PVA-SiO2-citral composite film and blend film were increased while the elongation at break decreased,the water contact angle increased but the surface of the film material became rougher.At the same time,the changes of structure and crystallization properties were observed,the lamellar spacing decreased.3.Study on the effect of PVA-based composite membrane material on storage and preservation of eggsVirgin PVA film,PVA-SiO2-citral composite film and blend film were applied in egg coating for preservation,and compared with the uncoated group,the effects of three kinds of film materials on the storage and preservation of eggs were studied.The results showed that treatment of egg coating could effectively reduce the total number of colonies on the eggshell surface,and delay the change of egg quality.It made the weight loss rate and albumen pH increasing slowly,delayed the decline of egg yolk index and haugh units、thick protein thinning、the disappearance of banding and the appearance of scattered yolk.In the treatment group of PVA-SiO2-citral composite membrane and blend membrane,there was no scattered yolk phenomenon in the storage of eggs within 10 weeks.The shelf life of eggs was prolonged by all coating treatment group.The preservation effect of blend film was the best,it can prolong the shelf life of eggs to more than 8 weeks.