An Innovative Method for Heating the Core of Starchy Food by Microwave Irradiation

Abstract

A new type of noodle that is pre-cooked (gelatinized) in the center only, leaving the surface uncooked (ungelatinized), was produced using microwave heating at ,./* MHz. Temperature distribution in the noodle during microwave heating varied with diameter῍ When the noodle with a diameter of +/ mm was heated, the temperature at the center of the noodle reached 0*ΐ in + min, while the surface temperature was .*ΐ. As a result, the starch granule could be gelatinized only in the center of the noodle. Starch granules in the noodle were confirmed to be gelatinized using polarizing microscopy. On the other hand, heating the noodle with a diameter of 1 mm produced a rapid increase in temperature with microwave irradiation, and the di#erence in temperature between the center and the surface was small. Though we tried to gelatinize only the center of the noodle with a diameter of 1 mm by microwave, the entire cross-section of the noodle was gelatinized. In order to gelatinize only the center of the 1-mm noodle, we utilized the di#erence in dielectric characteristics of the microwave between ice and water. That is, we froze only the surface of the noodle (the center remained unfrozen), heated the sample by microwave, and confirmed by polarizing microscopy that starch granules in the noodle were gelatinized while the surface molecules were not.(Received Jan. ,2, ,**/ ; Accepted Jul. ,/, ,**/)