Optimization of whole egg liquid sterilization technology using high pressure CO2

Abstract: The production of egg liquid is often contaminated with Salmonella. Eggs and their products are at a higher risk of infection or contamination of Salmonella, with up to 23.1%. In the traditional thermal pasteurization process, egg protein is prone to degeneration coagulation. For the purpose of killing salmonella and reducing the functional properties of the egg liquid, in this experiment, we used high pressure carbon dioxide (HPCD) to sterilize salmonella in whole egg liquid. HPCD mainly uses the synergistic effect of temperature (5-60 ℃) and CO2 pressure (0-50 MPa) to diffuse CO2 molecules into the medium and control the metabolism of microorganisms by acidification, chemical action and mechanical action. In order to achieve the purpose of sterilization, this study examines the effects of pressurized carbon dioxide, temperature, and stirring speed on the bactericidal effect of Salmonella in whole egg liquid. Single-factor analysis was conducted to measure the effects of pressurized carbon dioxide, temperature, time and stirring speed on the sterilization efficacy. On the basis of single factor, Box-Benhnken was used to optimize the Salmonella sterilization parameters and a quadratic polynomial model was established for the logarithmic reduction of viable count of Salmonella. At the same time, the effects of pasteurization and HPCD sterilization on the particle size, foaming, emulsifying and rheological properties of the whole egg liquid were also investigated. Through the Design-Expert software, the variance and significance of the regression model were analyzed, and we can conclude that the effects of pressurized CO2, temperature, time and stirring speed on Salmonella inactivation are mostly significant (P<0.000 1). The interactions between pressurized carbon dioxide and time, pressurized carbon dioxide and stirring speed, temperature and time, temperature and stirring speed, time and stirring speed are mostly significant (P<0.000 1). The interactions between stirring speed and temperature are significant for sterilization(0.000 10.05). Under the condition that the pressurized carbon dioxide, temperature, time, and stirring speed were 30 MPa, 40 ℃, 60 min and 125 r/min, respectively, lethal logarithm could reach 7.25. Compared with pasteurized egg liquid, the shelf life of the whole egg liquid treated with HPCD has been extended by 39 d; the foaming ability and foaming stability of whole egg liquid increased by 53.63% and 2.38% respectively (foaming ability: from 111.51% to 140.30%; foaming stability: from 80.72% to 92.14%). HPCD sterilization increased the absolute value of Zeta potential (from 4.71 mV to 7.66 mV), which improved the stability of the emulsion. After HPCD treatment, the rheological properties of whole egg liquid had no significant difference with the original egg liquid. The whole egg liquid of particle size, storage modulus and loss modulus decreased by HPCD treatment, showing the characteristics of pseudoplastic fluid. However, the foaming ability of whole egg liquid reduced with pasteurization (from 111.51% to 86.67%); the foaming stability of whole egg liquid increased (from 80.72% to 89.76%). Pasteurization reduced the absolute value of the Zeta potential of the egg liquid (from 4.71 mV to 1.36 mV), and the whole egg liquid after pasteurization increased particle size, denatured protein aggregation, and increased storage modulus and loss modulus. This study provides reference for the sterilization of egg liquid products with HPCD sterilization technology.