This study attempted to prepare a hydrolysate of corn gluten containing powerful ACE inhibitory activity and higher solubility, which could be used as a physiologically functional food material. The digestion of starch at 80degreesC resulted in more removal of the starch from the corn gluten than that at 60degreesC. More than 95% reducing sugars as enzymic digests of starch was removed by washing three-times. As for the thermal treatment effect on the increase of degree of hydrolysis (DH), degree of increase of protein content (slope) was 6.30 mg/ml min at 100degreesC, 4.40 mg/ml min at 80degreesC and 2.29 mg/ml min without heat treatment. After 45 min of heat treatment the increased ratio of protein content was greater than those by other heat treatments. After the pretreatment of corn gluten, hydrolysis with Flavourzyme, among six commercial proteases, resulted in the production of the hydrolysate with the highest ACE inhibitory activity, and with Protamax, the second highest ACE inhibitory activity was obtained. Flavourzyme hydrolysate of corn gluten at the 4% level was easily and completely soluble between pH 2 and 9. Water sorption of the hydrolysate slowly increased up to 0.8 of water activity and greatly increased at higher than 0.8 of water activity. (C) 2003 Elsevier Ltd. All rights reserved.