Abstract
The removal of dissolved oxygen in sudachi juice was examined by nitrogen gas pressurization. The direct pressurization of sudachi juice with nitrogen gas decreased the amount of dissolved oxygen in it. When sudachi juice was compressed directly with nitrogen gas, more oxygen could be eliminated by applying higher nitrogen gas pressure and by taking more time. Repetition of pressurization and depressurization with nitrogen gas could shorten the time to remove oxygen : when the compression of 10MPa at 30°C for 30s was repeated 3 times, the dissolved oxygen reduced to less than 1mg/l. Furthermore, the amount of dissolved oxygen could be decreased to 0.02mg/l by the continuous repetition of pressurization and depressurization treatment : 7 times×20s. From the facts described above, we may conclude that the repetition of pressurization and depressurization of liquid food with nitrogen gas is very effective to remove the dissolved oxygen in it. On the basis of an organoleptic test, it was found that the flavor of sudachi juice could be retained even if the compression and decompression was repeated under the following conditions ; pressure : 10MPa, temperature : 30°C, time : 1min (20s×3, 30s×2, 1min×1). Since the compression treatment of sudachi juice with nitrogen gas can get rid of the dissolved oxygen with holding its flavor, this method can be applied to the long-term preservation of sudachi juice without deterioration of its quality.
