Study On Effects Of Ultra-High Hydrostatic Sterilization On Liquid Egg White

Ultra-high hydrostatic pressure sterilization (UHHP) technology is a new type of cold sterilization techniques, due to its superior to traditional heating sterilization, which received extensive attention. In this paper, liquid egg white from fresh eggs as the raw material, we have studied the effect of sterilization and physical and chemical properties of proteins for liquid egg white using UHHP. Finally, the storage shelf life of packaged liquid egg white has been predicted.By testing the fresh eggs from market and found that the total number of bacteria in liquid egg white is about104cfu/mL, the detection rate is100%.The main decayed microbiology was E. coli detection rate at56%in liquid egg white, non-detection of Salmonella and Staphylococcus aureus.We considered the total number of bacteria as an indicator to study the influence of bacteria death rates with pressure, holding pressure time and pH for the liquid egg white. The results showed that the impact of pressure was the greatest, followed by the holding pressure time. Death rate of bacteria increases with the pressure and holding pressure time increasingly; the death rate at99.97%with300MPa,15min, pH8.1of liquid egg white, and the initial total number of bacteria fell from40000cfu/mL to12cfu/mL, in line with the national health standards.We applied ultra-high hydrostatic to sterilize E.coli at different growth stage which accessed in liquid egg white. The death law and resistance to pressure of the E.coli in liquid egg white were investigated. Death characteristic curve of E.coli were fitted by Linear model and Exponential model, respectively. Exponential model fitted better, E.coli in a steady growth stage had a stronger pressure resistance, and we concluded the pressure resistance parameters of E.coli:Dp and Zp.There have a greater impact of physical and chemical properties of the liquid egg white with UHHP. With300MPa-350MPa and10min-15min, the foaming capacity and foam stability of protein were the best. At the same time, there were the high content of surface sulfhydryl group in liquid egg white, and its trends of altering similar to foam stability. In addition, due to denaturation of protein caused decrease of solubility, emulsification and hydrophobicity of liquid egg white in varying degrees.We have researched storage period of samples of liquid egg white with processing at300MPa and15min. A microbial growth kinetics model was applied to fitting experimental values at4℃,14℃and24℃. The results showed that Gompertz equation could well describe the growth curve bacteria, and gives dynamic model of corresponding temperature. Using the square root (Belehradck) model, we have studied the impact of temperature on kinetics law of bacterial growth. There was a definite correlation between temperature (T) and maximum specific growth rate (μmax) as well as the lag time (Lag). Thereby establishing a shelf life prediction model and it is well verified with the storage sample at10℃and20℃.