Study On The Sterilization Technology Of Raw Egg

Eggs are rich in nutrients and occupy a high proportion in the food consumption of Chinese residents.With the improvement of people’s living standard and the diversified development of diet,Japanese and Korean cuisine develops rapidly in our country,so the consumption of raw eggs increases greatly.Under the influence of the feeding environment,fresh eggs are at risk of being contaminated by pathogenic bacteria,which affects the food safety of consumers.In actual production,thermal sterilization and ultraviolet sterilization technologies are generally used to sterilize eggs.Thermal sterilization at home and abroad has been relatively mature,but mainly used in liquid egg sterilization;Ultraviolet sterilization is widely used in eggshell surface sterilization,but its penetration is poor,so it is difficult to effectively sterilize egg contents.Therefore,it is urgent to study and establish sterilization methods for fresh egg contents to ensure the safety of raw eggs.In this paper,the feasibility of single thermal sterilization and combined thermal and ultrasonic sterilization in the sterilization of fresh eggs was explored,the technological parameters of sterilization were determined through experiments.The main research contents and results are as follows:1.The feasibility of applying single thermal sterilization to the sterilization of raw eggs was explored.The results showed that single thermal sterilization could not meet the sterilization requirements of E.coli in eggs.First established through the experiment with shell egg protein critical denaturation curve in the heating process,and draw lessons from liquid egg pasteurization conditions,refer to the eggs of pathogenic bacteria of Escherichia coli,Salmonella lethal temperature,select 1～5min,temperature 60～65℃,the design of Central Composite center combination experiment,with whole egg liquid to two factors,five levels of response surface analysis,it is concluded that a single heat sterilization,the optimal conditions for:At 64.8℃and 4.5min,the theoretical sterilization logarithms of total bacterial colonies,coliforms and Salmonella were N_k1=2.22,N_k2=4.57 and N_k3=5.24,respectively.Verification test was carried out with shell eggs,and the actual sterilization log values were N_k1=1.034±0.046,N_k2=2.216±0.089,and N_k3=0.768±0.022,respectively,which did not meet the five logarithm sterilization requirements proposed by the American FDA.2.Aiming at the deficiency of single thermal sterilization,ultrasonic wave was introduced to produce cavitation effect,and a fresh egg sterilization method based on combined thermal and ultrasonic sterilization was established Select three influencing factors of temperature,time and ultrasonic power are studied,according to the results of single factor experiments,choose time 3～7min,temperature 45～65℃,ultrasonic power 600～840 W,combination experiment design Box-Benhnken center,with whole egg liquid three factors and three levels of response surface analysis,it is concluded that the optimal sterilization conditions for 7 min,62℃,840 W,coliform bacteria and salmonella theory of sterilization of numerical N_k2=5.685,N_k3=5.550.Validation tests were conducted on fresh eggs with shells,and the actual sterilization logarithm values were respectively N_k2=5.278±0.170 and N_k3=5.034±0.189,which met the five logarithm sterilization requirements proposed by the American FDA.The results showed that the combination of hot and ultrasonic sterilization could effectively sterilize egg contents.3.The changes of fatty acid content in eggs under different heating conditions were studied,which provided reference for further optimization of sterilization process parameters considering protein denaturation,microbial indicators,flavor and taste,nutritional components and other factors.It was found that the fatty acid content of different brands of eggs was quite different due to the multiple differences of strengthening methods and breeding methods.Compared with the fresh whole egg liquid,the heating process of hot spring eggs had the least effect on the fatty acid content of omega-3 eggs.The contents of PUFA,EFA and DHA decreased by 0.08%,0.14%and 1.15%,respectively.The content of PUFA,EFA and DHA in soft boiled eggs decreased by 1.01%,0.55%and 4.23%,respectively.The fatty acid composition of cooked eggs changed the most,PUFA decreased by 1.22%,EFA decreased by1.29%,DHA decreased by 5.77%.The results showed that,from raw eggs,hot spring eggs,soft boiled eggs to fully cooked eggs,with the increase of maturity,the loss rate of fatty acids in eggs gradually increased,but the overall loss was small,indicating that heating had little effect on the fatty acids in omega-3 eggs.4.The heat-ultrasonic combined sterilization method established in this study can not only enhance the thermal sterilization effect and reduce the required sterilization temperature,but also overcome the shortcoming of poor UV penetration to achieve the purpose of sterilization of egg contents.Compared with other emerging sterilization technologies such as high-voltage pulsed electric field sterilization and high-density carbon dioxide sterilization,this method is simple in design,low in cost,low in energy consumption and easy to be popularized.It can be used in the sterilization of fresh eggs in Japanese and Korean restaurants to ensure the safety of raw eggs and has a good application prospect.