Influence of the Physical Form of Processed Rice Products on the Enzymatic Hydrolysis of Rice Starch in Vitro and on the Postprandial Glucose and Insulin Responses in Patients with Type 2 Diabetes Mellitus

Abstract

The manufacturing processes used determined the physicochemical properties of the three kinds of rice food, garaeduk, bagsulgi, and cooked rice. The initial rate of hydrolysis by porcine pancreatic α-amylase (PPA) was affected by the food form. The firmer structure of garaeduk was apparently responsible for the difficulty in maceration, resulting in less digestion than with easily digestible food for the same maceration time. The initial rate of hydrolysis of each rice product by PPA increased with increasing maceration time in a Waring Blender for all of the processed rice products. The postprandial glucose and insulin responses to the three processed rice products were also studied in ten patients with type 2 diabetes mellitus (4 men and 6 women aged 56.8±2.3 yr; duration of diabetes, 3.6±1.2 yr; body mass index (BMI), 23.7±2.6 kg/m²; fasting serum glucose, 143.9±5.1 mg/dl; serum insulin, 20.8±2.2 μU/ml). Each subject ingested of the three rice foods after a 12-h overnight fast, and the serum glucose and insulin levels were measured over a 0–240 min period. The postprandial serum glucose and insulin levels at 90 min after ingesting bagsulgi and cooked rice were less than those at 60 min, while the levels at 90 min after ingesting garaeduk were higher than those at 60 min. Garaeduk also significantly decreased the incremental responses of glucose and insulin when compared with bagsulgi and cooked rice. The results suggest that garaeduk would be the most unlikely to increase the postprandial serum glucose and insulin levels among the three rice foods. The food form, which eventually differentiated each food by its specific surface area with the same degree of maceration because of the characteristic physical strength, therefore affected the rate of rice starch hydrolysis both in vitro and in vivo.