Alpha-amylase activity was determined in triplicate every 2 h during fermentation of the ข้าวต้ม using the kit Megazyme International Ireland Ltd. (Ceralpha method, 2004; ICC Standard No. 303), following the instructions of the manufacturer and expressed as Ceralpha Units (CU) per gram of product in dry matter, as described by McCleary, McNally, Monaghan, and Mugford (2002). One Ceralpha unit is the amount of α-amylase required to release 1 μM of p-nitrophenol from the substrate per 1 min, under the assay conditions.