| This research was designed to study:1.changes in the law about physical and chemical properties of eggs at different temperature condition during storage as well as sensory quality; 2.study the physical and chemical properties of OHAA film, and determine the appropriate solvent and forming processes, design the best OHAA formula by using response surface method to improve the performance of OHAA; 3.prepare nanoparticles by green water phase reduction, and analyze antibacterial properties of various antimicrobial agents, selecte the most efficient antibacterial material for composite OHAA coating; research the preservative effect of OHAA coatings on the fresh eggs, and to explore its surface membrane morphology and consumer acceptability compared with other coating materials.Experiments show that a series of internal quality changes during storage, such as thick protein gradually decreased; frenum becomes thinner till disappeared, become flat and loses its elasticity yolk, egg begins smelly, in the case of the higher temperature it changes more quickly. When stored at 25℃after 30 days, the weight loss is 7.28%, the relative density is 0.99, yolk index is 0.23, albumen pH is 9.23, Hough unit is 35.22; under 30℃the wight loss is 9.13%, the relative density is 0.97, egg yolk index is 0.29, egg albumen pH is 8.37, Hough unit is 30.12; under 35℃the weight loss is 11.03%, the relative density is 0.93, egg albumen pH value is 7.95, under 35℃after 24 days, egg yolk had been broken, unable to detect egg yolk index and Haugh unite.OHAA physical and chemical property is measured as follow:the density is 1.075g/cm3, before melting temperature is 45.8-47.1℃, melting temperature is in the range of 49.3-50.2℃. The colour tone is 218; the saturation is 25; the brightness is 232, and the colour is ivory white.The hardness is 1130.88±31.42; the adhesiveness is-2236.62±77.07; the coherentness is 0.61±0.06. The best ratio of ethanol and OHAA is 5:1. Optimization of conditions obtained by response surface method as 5g OHAA add 205g water,3.2g Twain 80,4g glycerol,11.8g palm oil.OHAA film forming process as follows:Weigh a certain amount of OHAA, melting and then add the appropriate proportion of the ethanol reagent and water stirring slowly, then adding other additives. By shear emulsifier on the balm of shearing, increase its emulsifying properties, and finally vacuum to remove air bubbles generated during preparation, OHAA coating preparation is completed at last.By using sodium citrate reduction method to prepare the stability of nano-silver sol, the reaction is convenient and green. UV spectrophotometry showed a significant absorption at 420nm, the average particle size is about 35nm, shape is cylindrical and spherical. X-ray diffraction demonstrates that their four peaks means only silver is there. Placing at room temperature for 3 months, it does not appear agglomeration, nor precipitation in the bottom, the solution remains limpid proves that nano-silver sol prepared with good stability. Comprehensive analysis of nano-silver antimicrobial, stability, durability, heat resistance, which means nano silver has significant advantages for antibacterial agents of OHAA composite coating. When the additive amount is 55μg/mL, the prepared composite OHAA coating performes a good antibacterial activity.The preservation experiments is tested by OHAA, chitosan, polyvinyl alcohol and AEO. The results show that all the material has a certain effect for preservation of egg, composite OHAA coating is the best through integrated assessment, followed by the AEO, PVA, and chitosan. After 5 weeks in storage, the weight loss of control group was 8.14%, the relative density was 0.93, yolk index was 0.19, pH value of 9.37, Hough unit was 33.41, eggs rating dropped to B grade. Weight loss of OHAA coating was 4.23%, the relative density was 1.00, egg yolk index decreased to 0.44 from the beginning of 0.34, pH values increased to 8.31 from the initial 7.68, Haugh unite down to 63.18 from the 75.35, egg quality maintained at A level, and the number of microorganisms within the eggs was controlled at a lower level. Observed by the SEM, OHAA film is uniformity and smooth, and covers eggshell effectively that obtained the preservation purpose. It will be a bright future for the research and application of this new preserving material. |
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