Development of a New Heating System by Combining Superheated Steam and a Hot Water Spray (Aqua-Gas^TM) and Its Application to Food Processing

Abstract

Superheated steam was applied to food processing because of advantages that include efficient heat transfer by latent heat and the prevention of product oxidation. Superheated steam solves problems such as water absorption and the dissolution of solid content from foods caused by hot water or saturated steam heating ; however, it causes low product yield due to its high drying capacity. In order to extend the application of superheated steam to food processing, a new oven system (Aqua-gas^TM) using superheated steam and micro droplets of hot water has been developed. In this system, a mixture of superheated steam and hot water was achieved under normal pressure by spraying pressurized boiling water into a heating chamber through a nozzle. It was found that Aqua-gas has a higher heat transfer rate than ordinal superheated steam, especially with cold materials. Fresh vegetables have been pasteurized effectively with little change in texture by heating with this system. The moisture content of the food product processed with this oven system can be controlled by regulating the amount of micro droplets used in the superheated steam. This system is currently used in the food industry for cooking potato salad, preprocessing meat, and in the pasteurization of fish products in Japan.