| In this paper,the effects of hydroxide ion and saline ions,and boiling process on albumen gel characteristic and protein structure were researched.Response Surface Methodology was used to optimize the pickling process technic of the breakfast egg on the basis of single factor experiment including dosage of sodium hydroxide,dosage of sodium chloride,and pickling time.During the optimization process of pickling,variation pattern of heat-induced albumen gelatinization,and related protein molecule structure and inter-molecule interaction were investigated in order to explore the method of regulating and controlling egg albumen gelatinization quality.Finally,the fresh-keeping method of coating the eggs with composite film to extend shelf life was researched.1.Research on effect of alkali and sodium chloride on egg product and optimizing the processing technologyOn the basis of single factor experiment,dosage of sodium hydroxide,dosage of sodium chloride and pickling time were selected as three factors of response surface experiment,and sensory evaluation values,hardness and elasticity of albumen gelatinization were chosen as three response value to optimize the pickling technic of egg production.The result of single factor experiment and response surface optimization experiment showed that the optimal pickling condition is that the adding amount of sodium hydroxide is 2.09%,the adding amount of sodium chloride is 23.05%,and pickling time is 4.64 d.The pickling time was changed to 5 d in view of actual production,and eggs were pickled under above-mentioned condition.After pickling,the hardness and elasticity of albumen gelatinization were 109.3 ± 2.3 and 73.4±2.1,and sensory score was 79.01±1.25 whose difference with theoretical value were less than 5%.2.Research on effect of pickling and boiling process on albumen protein intermolecular force and gelatinization characteristicsThe result showed that the free alkalinity content and NaCl content of liquid albumen increased significantly during the pickling time(p<0.05),and hardness of albumen gelatinization increased significantly at initial period(p<0.05),and decreased at last time.Gel strength,chewiness,elasticity,and cohesiveness of albumen gelatinization increased quickly at first(p<0.05),and became equilibrium gradually in the late,however,water-holding capacity of albumen gelatinization decreased significantly(p<0.05).The total SH content of liquid albumen decreased significantly during pickling time,however,which was also significantly more than albumen gelatinization,and SS bond content of liquid albumen increased significantly and was less than albumen gelatinization.The variation of interaction between protein molecules in liquid albumen was that the amount of ionic bond decreased,and the amount of hydrophobic interaction increased,and hydrogen bond was destroyed,and hydrophobic interaction of albumen gelatinization was much stronger than liquid albumen,and increased as the pickling time prolonged,and ionic bond of albumen gelatinization decreased significantly(p<0.05).The result also showed that proteins of liquid albumen degraded into small molecular-weight protein molecular during pickling time,and heat induced the protein aggregated into high molecular-weight proteins,and the molecular-weight of protein of albumen gelatinization became larger as the pickling time prolonged.3.Research on preserved effect of nano-modified PVA based composite materials and PVDC based material on eggs.Several composite materials including nano SiO2/TiO2 modified polyvinyl alcohol based liquid paraffin and beewax composite coating material(PVA composite group),pure polyvinyl alcohol coating material(pure-PVA group)and polyvinylidene chloride coating material(PVDC group)were selected to coat eggs,and uncoated eggs were regarded as CK group.Each group of eggs was put into environment whose temperature was 22℃ and relative humidity was 75±2%,and a few indicators including weight loss rate,pH values of albumen and yolk,NaCl content of albumen and yolk,total plate count and sensory evaluation value of breakfast eggs were detected regularly.The result showed that weight loss of eggs from PVA composite group(6.94%)and eggs from PVDC group(6.15%)were significantly less than uncoated eggs(14.36%),which reduced by 51.67%(PVA composite)and 57.17%(PVDC group)in comparison to uncoated eggs,and reduced by 14.95%(PVA composite)and 24.63%(PVDC group)in comparison to eggs from pure IV PVA group.The time of total plate count of each egg which was more than limiting value were 35 d(PVDC group and PVA composite group),20 d(pure PVA group)and 15 d(uncoated group).Based on various indicators,shelf life of each coated group were 35 d(PVDC group),30 d(PVA composite group)and 15 d(pure PVA group).Nano-materials and hydrophobic organics improved barrier property of pure PVA membrane,and barrier property of PVDC-based material is better than PVA-based materials,and which has great potential applications on egg products. |
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