| Fresh packaging has an important impact on the flavor quality and shelf life ofsalted duck eggs.The vacuum packaging is commonly used for preserving cooked salted duck eggs,of which higer energy consumption and lower mechanization,and could cause“white”pollution.Therefore,exploring new fresh packaging method for salted duck egg packaging are of great significance,which could reduce packaging costs,and improve production efficiency.In recent years,coating fresh-keeping technology has become a research hotspot.As an important coating fresh packaging material,polyvinylidene chloride shows the broad application prospects in the field of food,medicine,military,electronics.However,it has not been found to improve the packaging properties by modifying the nano materials.This paper proposes to study the packaging properties of PVDC-based nano-SiO2 composite materials,and as well as to explore the effect of nanocomposite on quality of salted eggs during storage,the detailed contents are as follows:1.Studies on the influence of surfactants on the dispersion system of nano silica aqueous solutionSelecting six different surfactants,we studied the dispersion stability of nano silica aqueous solution with different surfactants by using the gravitydepositionmethodcombined with the averageparticlesize determination.Preliminary screened out the effect of Sodium dodecyl sulfate(SDS)on the dispersion stability of nano SiO2 in water medium was the best,and the nano SiO2 aqueous solution with SDS as the surfactant had smaller particle size and uniform particle distribution.Then we studied the influence of different pH and different nano SiO2/SDS ratio on the surface modification of nano SiO2.The results showed that nano SiO2 modified by SDS could form a stable dispersion system under the acidic condition and the optimum range of pH was from 3.10 to 4.86.We also discovered that the nano material dispersion system had the minimum particle size distribution,when the ratio of SiO2/SDS was 0.7,and the minimum particle size was 207±14.2nm.2.Preparation and structural characterization of nano silica modified PVDC-based coating materialsSDS modified nano SiO2 particles were added to the PVDC emulsion by blending method,polyvinylidene chloride(PVDC)-based nanocomposite films with different amount of modified nano-SiO2 were fabricated by a solution-intercalation,film-casting method.Packaging properties of nanocomposite films was greatly influenced bynano-SiO2 content.With the increaseof nano-SiO2 content,the viscosity of nano composite films was significantly decreased and water vapor permeability and water resistance of films increased,but transparency property decreased.The mechanical properties of the composite film are also affected by the content of nano-SiO2.Results on scanning electron microscopy(SEM)revealed that PVDC-based coating material has good flatness when nano-SiO2 content is 0.12%.PVDC/SiO2composite films with 0.1%-0.12%nano-SiO2 addition was used to coating salted duck eggs based sensory evaluation.3.Effect of nano-SiO2 modified PVDC-based composites coating material on quality of salted duck eggs during preservation processSalted duck eggs that were coated withPVDC/SiO 2,unmodified PVDC material and SiO2/TiO2 modified PVA-based,namo-MMT modified PVA-based nanocomposite coating materialrespectively,were stored at 28?,70%relative humidity for 120 days,quality changes were detected during the storage process.The treatment of different coating could significantly decrease the bad quality changes(increase of loss of weight,TVB-N,total bacteria counts)(P<0.05),and prolong the shelf life of the salted duck eggs.The inhibition of PVDC/SiO2nanocomposite to increase of loss of weight,total bacteria counts,TVB-N,free fatty acids,pH changes of egg yolk and albumen was significantly higher than other coating materials(P<0.05).However,the TBARS of salted duck eggs didn't change significantlyduring preservation(P>0.05).The results of sensory evaluation indicated that PVDC/SiO2 composite coating materials could effectively preserve the quality of salted duck eggs. |
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