| AS is the famous Chinese traditional egg product, preserved eggs have realized modern automated production from traditional workshops. But the fresh packaging is the key factor of effecting its self life and flavor. So exploring a new fresh-keeping preserved egg method has great significance for simplifying processes, debasing packaging costs, mechanized operations, achieving degradable and energy savings. This paper on the basis of the lab study on modification for PVA-based composite coating material by nano-SiO2, determination of residual glutaraldehyde in PVA-based composite nano-SiO2material and its effect on fresh-keeping of preserved egg. The contents of this paper mainly composed by the following three parts:1. Study on modification for PVA-based composite coating material by nano-SiO2The PVA-based composite coating material was modified with nano-SiO2and its preparation method was optimized by response surface method. The mathematical model was built by using the water vapor transmission rate of formed film as response and nano-SiO2, steric acid, glutaraldehyde and reaction temperature as influencing factors. The water vapor transmission rate of formed film of optimal group decreased by50%(P<0.05) compared with that of the control group (PVA material). There were significant interactions among nano-SiO2, stearic acid, glutaraldehyde and reaction temperatur on the water vapor transmission rate of formed film, the addition of nano-SiO2could increase the added level of glutaraldehyde and improving reaction temperature could increase the added level of stearic acid in the composite coating material. Under the optimal conditions of coating-keeping fresh material by PVA:stearic acid0.55%, glutaraldehyde0.44%, nano-SiO20.040%,reaction temperature90.56℃within a certain range in100mL5%(W/VH2O) of the PVA solution. 2. Study on determination of residual glutaraldehyde in PVA composite nano-packaging materialGlutaraldehyde was crosslinker of polyvinyl alcohol (PVA) composite nano-packaging material and improved its synthetic properties of packing, but residual glutaraldehyde might affect safety of composite nano-packaging material. The extraction was carried out with ultrasound, The extracted glutaraldehyde was derivatized with2,4-dinitrophenylhydrazine (DNPH) and the derivative was analyzed by HPLC. It shows that in the range of glutaraldehyde content of0.2～5mg/L, the method was fast and accurate with a linear correlation of0.9997, average recoveries of76.8%～87.3%, a relative standard deviation of2.83%-4.08%and a minimum determination concentration of0.2mg/kg. The procedures are suitable for the determination of residual glutaraldehyde in polyvinyl alcohol composite nano-packaging material. The residual glutaraldehyde of PVA composite nano-packaging sample was24.55mg/kg and met the safety limit criterion of food-packaging material.3. Study on the storage preservation effect of preserved eggs by packaging of PVA-based nano-SiO2composite coating materialAll the preserved eggs of the four groups were stored at normal temperature for6months (temperature condition25-30℃) and the physical and chemical indicators, microbiological and sensory indicators of the eggs of groups were measured and compared by each other in the storage. The results showed that, after6months storage, the average water loss rate (11.19%) of the preserved eggs coated by PVA-based nano-SiO2composite coating material decreased by14.17%compared with the control group (13.05%). Moreover, the aerobic plate count (410CFU·g-1)and pH value(9.55) also decreased significantly (p<0.05).This result indicated that the twice coating the preserved eggs with PVA-based nano-SiO2composite coating material could effectively prevent the water loss in preserved eggs, inhibit microbial growth and reproduction which well protected the color and flavor of salted duck eggs for6months storage. |
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