纳米Fe3+/TiO2改性聚乙烯醇基紫胶复合膜对鸡蛋的保鲜效果

摘要

Eggs are highly nutritional food, and contain a variety of amino acids, proteins, minerals, lecithin, sterols, and other essential nutrients that can be fully absorbed by human body. However, the quality of unsterilized and unwashed eggs will deteriorate rapidly during storage, including such conditions as water evaporation, weight loss, and yolk coefficient decrease. In such cases, cleaned and sterilized eggs can effectively suppress harmful pathogens and extend the shelf life of egg products. But cleansing and sterilization could possibly destroy the outer shell membrane of eggs, which causes the eggs to be vulnerable to microbial contamination, as the outer shell membrane has been destroyed. The outer shell membrane can prevent microbial invasion of eggs, so the destruction of the outer shell membrane makes water evaporate through the pores of the shell membrane, and finally causes the spoilage of fresh eggs. Therefore, one of the most effective ways of keeping eggs fresh is to coat eggs with an antimicrobial film. In this paper, polyvinyl alcohol/shellac/ nano-Fe3+/TiO2 composite film prepared by the author is used to preserve eggs by fully covering them. The composite film materials include nano-Fe3+/TiO2which is fabricated by blending nano-Fe3+ with nano-TiO2in a solution and then calcining them at 400℃ for 3 hours, PVA (polyvinyl alcohol), and shellac. For antimicrobial film preparation, the first step is preparing the coating film solution by slowly dissolving 5 g/mL PVA in distilled water while stirring and then heating the coating film solutions up to 85°C. The second step is incorporating nano-Fe3+/TiO2, which is dissolved in anhydrous ethanol, into the coating film solution and then shocking composite film solutions with ultrasonic at 65 W/L for 15 min in an ultrasonic bath. The third step is incorporating succinylated monoglycerides and shellac, which are dissolved in anhydrous ethanol into PVA/nano-Fe3+/TiO2 composite film solutions, while stirring and then cooling the solution to 60°C. After preparing the composite film solutions, fresh eggs were used as experimental material and were cleaned and disinfected, and then were coated with composite film. Sensory quality, weight loss, Haugh units (HU), egg yolk coefficient, chromatic aberration, pH, and total number of colonies of different groups were measured, and quality changes of different treatment groups were compared during their storage period. The result shows that quality indicators of fresh eggs in different groups significantly changed (P<0.05). The total number of colonies of fresh eggs during the storage period had a significant upward trend. The shelf life of fresh and cleaned eggs was 20-30 d depend on the change of quality indicators. The shelf life of fresh eggs coated by PVA single film was up to 50-60 d, and the shelf life of fresh eggs coated by PVA/shellac/nano-Fe3+/TiO2 composite film was up to 70-80 d. In addition, the preservation properties of fresh eggs coated by PVA/shellac/nano-Fe3+/TiO2 composite film were significantly better than fresh eggs coated by PVA single film, and PVA/shellac/nano-Fe3+/TiO2 composite film significantly reduced the rate of change of weight loss, Haugh unit, and yolk coefficient of fresh eggs during storage period (P<0.05) compared to other groups. Therefore, PVA/shellac/nano-Fe3+/TiO2composite film achieved the purpose of extending the shelf life of eggs and it can be applied to package fresh eggs. This paper provides reference for the application of nano-modified composite film materials in the preservation of fresh eggs.%为了探究纳米Fe3+/TiO2改性聚乙烯醇基紫胶复合膜对清洁鸡蛋的保鲜效果，该文中将新鲜鸡蛋分组后涂上聚乙烯醇（polyvinyl alcohol）单膜和纳米Fe3+/TiO2改性聚乙烯醇基（polyvinyl alcohol）紫胶复合膜后，测定储藏过程中各组鸡蛋的感官品质、失重率、哈夫单位（haugh units，HU）、蛋黄指数、色差、pH值和菌落总数等，再对各项指标进行统计分析。结果表明：各组鸡蛋的品质指标在储藏过程中都有显著变化（P<0.05）；贮藏过程中纳米 Fe3+/TiO2改性聚乙烯醇基紫胶复合膜组的鸡蛋品质指标显著优于聚乙烯醇单膜组和未涂膜组（P<0.05），表明复合膜对鸡蛋的保鲜效果优于聚乙烯醇（polyvinyl alcohol）单膜和未涂膜。未处理的和清洗消毒过的，聚乙烯醇基单膜涂膜包装后的，和纳米 Fe3+/TiO2改性聚乙烯醇基紫胶复合膜涂膜包装后的清洁鸡蛋，其保质期分别为20～30、50～60和70～80 d，表明聚乙烯醇单膜可延长鸡蛋保质期30 d左右而复合膜可延长达50 d左右；该研究结果为纳米改性复合涂膜材料在新鲜鸡蛋贮藏保鲜上的应用提供参考。