| Summary: | 博士 === 國立屏東科技大學 === 食品科學系所 === 105 === Rice, the foremost food crop, is a staple food for people around the world. Moreover, rice varieties, processing, cookeries and physicochemical properties presents various GI (Glycemic Index) values. Most rice varieties are classified as high-GI foods. According to researches, people who have high-GI diets may increase risk of obesity, type 2 diabetes, diabetic complications, cardiovascular disease and some cancers. Low-GI diets, however improve insulin sensitivity and blood lipid and blood glucose level. Therefore, it is important to pay close attention to postprandial blood glucose and GI value of food. In order to study GI value of food, we investigated different methods of measuring GI values and physicochemical properties of foods in this study: (1) evaluating accuracy of GI by three different blood sampling methods; (2) measuring glycemic response and GI with gluten protein, dextrin fiber or canola oil added in cooked rice; (3) comparing effects of different cookeries, storage temperatures and storage durations on GI of cooked rice. First, we compared three different blood sampling methods (based on capillary whole blood, capillary plasma and venous plasma, respectively) of glycemic response, IAUC (incremental area under the blood glucose response curve) and GI for steamed rice, rice porridge and rice that stored overnight. The results showed that rice porridge produced the highest mean GI and mean IAUC (99.3 ± 0.6 and 4008.6 ± 390, respectively), followed by steamed rice (92.1 ± 0.4 and 3710 ± 363, respectively), and then that stored overnight rice (90.7 ± 0.4 and 3677 ± 366, respectively). In terms of blood sampling method, venous plasma show higher precision and lower coefficient of variation (CV) of GI, IAUC and glycemic response than other sampling method. Secondly, rice mixed with gluten protein, dextrin fiber or canola oil was tested for GI values. Venous plasma blood sample was taken to observe glycemic effect of rice according to first investigation. In this study, we determined the dose-response and mixture interaction effects of gluten protein, canola oil, and dextrin fiber combined with a portion of white rice on glycemic response and GI. The results showed that white rice has a GI value of 93.8±2.8. Supplementation with various amounts of canola oil and dextrin fiber reduced the GI slightly, whereas gluten protein significantly (p < 0.05) reduced the GI from 93.8 to 84.9 and 83.1, respectively. Analysis of the interaction of gluten, lipids, and dextrin on GI by using three-way ANOVA revealed that significant effects on GI value were found with gluten (p < 0.01) and dextrin (p < 0.05). Moreover, adding a gluten protein and dextrin fiber mixture yielded a larger glycemic control effect than adding a lipid and dextrin fiber mixture did. In conclusion, Food processing supplements gluten protein with rice products may associated with a reduction in overall postprandial glycemic response and induced a lower GI in healthy people. Finally studying, we examined the glycemic response of white rice to determine the effects of storage temperature (-20°C, 0°C, and 4°C) and storage duration (1, 3, and 5 days). Results were compared with cooked white rice (control, 25°C). Measurements were performed on Days 1, 3, and 5 to test the glycemic index (GI), incremental area under curve (IAUC), and blood glucose response. The results showed that the mean GI was highest for the control (93.5 ± 3.6), followed by those for the -20°C (87.4 ± 3.1), 4°C (84.1 ± 2.8), and 0°C (84.1 ± 2.7) test foods (Day 1). The GI values differed significantly with the storage duration (p < 0.05). In conclusion, white rice stored at 0°C for 5 days has the lowest glycemic response. Moreover, control group (25°C) exhibited the highest GI. In recent years, food choice and eating habits have changed dramatically. Our findings may serve as a reference for developing fast-food or low-GI emerge and conform to nutrition and health concepts applied to production of rice products.
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