In liquid products such as cooking oil, the fatty acids, the source of the odor, are separated from the water vapor and collected in a gas state. Propylene glycol solution is sprayed and released into the absorption tower. In this area, the gas absorbs the source of the odor and discharges it to the outside of the process system by a vacuum exhaust. During deodorization, the propylene glycol solution absorbs water vapor and regenerates it as dilute, increasing concentration, and then being sent back to the absorption tower. This regeneration requires a heating source and a refrigeration unit. The fatty acids are collected by passing through the filters installed in the propylene glycol solution circulation system.