DESIGN OF BREWERY PASTEURIZATION METHOD BY HIGH PRESSURE CARBON DIOXIDE

摘要

The compressed CO_2 was supplied from the CO_2 cylinder to the steel vessel containing yeast-water mixture until the pressure inside the steel vessel reached a desired pressure level. The steel vessel was kept at the prescribed pressure level during the treatment period. After the treatment, the pressure inside the vessel was released to the atmospheric pressure within the evacuation time by controlling the relief control valve. The sterilization effect was evaluated by vial counting the treated sample taken from the steel vessel. Several experiments have been performed varying each factor such as the total treatment time, the evacuation time and the applied pressure. As a result, it was verified that these factors are strongly related to the sterilization effect. In addition, it was observed that increase of the treatment time could enhance the concentration rate of CO_2 in the mixture. Furthermore, it was concluded that fast depressurizing rapidly expanded CO_2 penetrated into each yeast cell. Also, the experimental results showed that when treatment time is longer, the pressure becomes higher, and the evacuation time is shorter, thus, a better sterilizing effect was obtained. Contrary to the results above, both the treatment time and the evacuation time rarely affected sterilization effect under supercritical condition. By adopting Supercritical condition, a desirable result could be achieved with shorter treatment and longer evacuation time. Thus, as long as supercritical condition is adopted for test, either fast evacuation time or long treatment time is not essential any more.