Selective peroxidase inactivation of lightly milled rice by superheated steam

• Superheated steam (SS) was effective for inactivation of rice peroxidase.
• SS treatment could maintain the natural physicochemical properties of lightly milled rice (LMR).
• SS treatment caused almost no fissures to LMR.
• Texture of LMR may be related to fissures and micro-mechanical behavior.

Superheated steam (SS) was used to inactivate peroxidase of lightly milled rice (LMR) in this study in order to extend shelf-life of LMR. Meanwhile, the effects of SS on physicochemical properties of LMR were evaluated. Compared with hot air (HA), SS could inactivate peroxidase of LMR within a shorter time and result in lesser reduction of moisture content. SS caused much less fissures and alteration of micro-mechanical behavior (intercellular and intracellular cleavage) to LMR than HA did. SS-stabilized LMR, of which peroxidase was inactivated by SS, maintained their natural physicochemical properties including appearance (whiteness of uncooked rice and morphology of cooked rice), cooking quality (water absorption, volume expansion ratio and total solids loss), and texture profile (hardness, adhesiveness chewiness and cohesiveness). Physicochemical properties of LMR were closely connected with fissures. The morphology and texture of cooked LMR might be partly explained by the micro-mechanical behavior of uncooked LMR. SS would be a promising technology for inactivating peroxidase and retaining natural physicochemical properties of LMR simultaneously.