Development of a new, continuous, inline, Aqua-gas drying system and its application to drying perilla leaves while retaining the functional components and antioxidant activities

We tested a continuous inline food-drying system that consists of a conveyor belt passing through three chambers containing Aqua-gas (R) (AQG), superheated steam (SHS) in the near-anaerobic state, and cooling nitrogen or carbon dioxide gas. Common viable and coliform bacteria were sterilized by the AQG, SHS, AQG -> SHS, and steaming treatments. The SHS, AQG?SHS, hot air (HA) drying, and steaming?HA drying treatments each produced dried perilla leaves with a final wet weight-based water content of <10 %. Most of the treatments preserved the a-linolenic acid content. The rosmarinic acid content was greatly increased by SHS and AQG?SHS treatment but greatly decreased by HA drying treatment. The AQG treatment produced significantly higher antioxidant activity, which was greatly increased by the SHS and AQG?SHS treatments due to the increase in the total soluble polyphenol content by the blanching effect, but the activity was greatly decreased by HA drying treatment. Radical-scavenging activity was well correlated with the total soluble polyphenol content. This prototype continuous inline AQG drying system both retains functional components and enables more efficient processing.