Abstract
Superheated steam (SHS) was applied to food processing because of advantages including efficient heat transfer by latent heat, and prevention of product oxidation. SHS heating solves problems such as water absorption and 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. To fix these problems, a new system using SHS around 115°C and a spray of hot water micro droplets (WMD) has been developed. The SHS+WMD system has simultaneously improved the quality and yield of blanched potatoes and other vegetables. In addition, it was found that WMD increased the heat transfer efficiency of SHS. This was presumably because WMD reduced the thermal resistance of the condensed water layer on the product surface by stirring the condensate. Due to this effect, the required time for the surface pasteurization of some kinds of raw vegetables decreased. A standard plate count of bacterium on cucumber fruit decreased from 105 CFU/g to 300 CFU/g with a slight texture change by SHS+WMD heating for 30 s. The SHS+WMD system is currently used in the food industry for cooking potato salad, and preprocessing meat, as well as the pasteurization of fishery products in Japan.
