To investigate the primary factors affecting the efficiency of microwave heating pretreatments in inactivating lipase in naked oat kernels, the effects of temperature, duration of heating, moisture content of oat kernels, tempering time and packaging conditions on the inactivation of lipase activities were examined. Microwave heat treatment for 45 s was found to inactivate 98-99% lipase in oat kernels (20 g in polyethylene package) with 11.1% moisture content, thereby stabilizing oat kernels against triglyceride lipolysis. The steam quantity played a crucial role in lipase inactivation. A trend was found: the higher the quantity of steam evaporated, the lower the residual lipase activities remained in whole kernels. Pretreatments, such as vacuum packaging, increasing the moisture content of oat kernels to a range of 17.0-25.0% from 11.1%, and conducting heat treatments as soon as the kernel moisture contents were adjusted, were found to be beneficial in accelerating steam evaporation; the efficiency of microwave heating on lipase inactivation was thereby increased. (c) 2009 Elsevier Ltd. All rights reserved.