1 Brief description of the process flow
Instantaneous pasteurization consists of a three-stage plate heat exchanger, a high-pressure variable frequency beer pump, a heating system, a heat preservation system, a cooling system, a CIP cleaning system, a piping system and a control system. The operation procedure is as follows:
① Start the CIP automatic cleaning program, and perform 10 minutes, 75 ℃, 2%~3% alkaline washing, 5 minutes of hot water flushing, and 20 minutes of 80 ℃ hot water sterilization on the pipes, equipment, and pumps through which the beer passes in the instant pasteurization system;
② Start the automatic cycle heating program, and use 4 ℃ deoxygenated water to automatically circulate and heat in the system. When the temperature rises to 70 ℃, the normal program will be automatically run
③ The 0 ℃ cold beer from the sake tank is pressurized by the high-pressure pump and enters the second section of the plate heat exchanger. It is convectively exchanged with the 70 ℃ beer that has just been insulated and sterilized and needs to be cooled, so that it is preheated to 64 ℃, and then enters the third heating section. It is heated to 70 ℃ with 0.05 MPa (gauge pressure) steam, and then enters the insulation pipe for insulation for 15 s;
④ After completing the sterilization process, the 70 ℃ beer is returned to the second section of the heat exchanger, and the heat energy is transferred to the 0 ℃ cold beer, so that it is cooled to 12 ℃, and then enter the first section of the heat exchanger, where it is cooled to 2~4 ℃ with a refrigerant of -3~-5 ℃, and then transported to a buffer tank that has been CIP cleaned and back-pressured with CO, and the beer is put into bottles using an aseptic cold filling method, and then the beer temperature is raised to 30 ℃ by a bottle warmer before labeling.
2 Key parameters and control points
Maintaining a constant, one-time sterilization temperature (70 ℃) is the key to the instantaneous pasteurization system. If the sterilization temperature is high, the heat load is large, which will cause serious damage to the shelf life, and at the same time, many flavor substances will be damaged, proteins will be denatured, and the colloidal stability and foam stability of the beer will be destroyed; if the sterilization temperature is low, the biological stability of the beer cannot be guaranteed. The core of the control is to first use dehydration cycle heating to preheat the equipment to normal working conditions, and then use the temperature detector set on the insulation pipe to automatically control the feedback through the computer and the heating steam regulating valve.
Maintaining the sterilization time of 10s at a sterilization temperature of 70℃ is another important control point for controlling the heat load of beer and ensuring the shelf life of beer. Under the premise that the length and volume of the insulation tube are constant, stabilizing the flow of beer through the instantaneous sterilizer is equivalent to controlling the sterilization time. The control method is to use the flow meter at the beer inlet to detect the flow feedback and automatically control the speed of the high-pressure variable frequency beer pump.
Another important indicator of beer is the content of CO,. The solubility of CO in beer is closely related to the temperature and pressure of beer. At a sterilization temperature of 70℃, to ensure that the CO dissolved in the beer is not released, the system pressure must be stabilized at 0.8MPa. If the pressure is lower than this value, the carbon dioxide in the beer begins to overflow, resulting in a large amount of beer foam, making production operations difficult, which will not only destroy the sterilization effect, but also consume the foam-generating substances, so that the CO content does not meet the requirements. The control method is to control the heat exchanger outlet regulating valve through the pressure detection at the outlet of the plate heat exchanger.
3 Calculation of sterilization unit
The sterilization degree of general beer is measured by Pu value, that is, Pasteur sterilization unit. The Pu value calculation formula is: Pu = tx1.3930-60, where t is the sterilization time (min) and T is the sterilization temperature (℃). The Pu value of 70 ℃, 10 s is 6.85 units; experiments show that when the lethal Pu value reaches more than 5 units, the beer yeast can be effectively killed and the yeast will no longer reproduce. This Pu value is very beneficial to the flavor stability and freshness of beer, and this indicator is also better than other sterilization methods. 2.4 Aseptic cold filling Aseptic beer after pasteurization can only achieve a long shelf life and good biological stability by aseptic cold filling. Aseptic cold filling means that under the premise of beer sterility, the filling environment, packaging materials and auxiliary materials must be aseptic during the production process.
4 Advantages of flash pasteurization
2.1 The beer produced by flash pasteurization is better than pure draft beer produced by membrane filtration in terms of foam retention, and is equivalent to pure draft beer in terms of aging taste control. The shelf life of both is much longer than that of beer produced by tunnel spray pasteurization.
2.2 Flash pasteurization has the advantages of low consumption, low cost, simplicity and ease of use.
2.3 Both flash pasteurization and membrane filtration require aseptic filling technology, and the equipment investment is relatively high. The actual operation process is much more complicated and difficult than tunnel sterilization. Among them, membrane filtration does not require heating and is a recognized energy-saving technology. Flash sterilization also consumes a certain amount of heat energy, and the impact of heating on CO2 dissolution must also be considered.