A comparative study regrading traditional cooking processes in Northern Thailand influence phytochemical content, antioxidant capacity and inhibition of key enzyme activity in glutinous rice

Abstract

The aim of this study was to investigate traditional cooking processes for glutinous rice in order to determine the optimum rice type ratio, pre-cooking preparation technique and cooking method for the preservation of bioactive compounds that inhibit the activity of key enzymes involved in carbohydrate digestion. Samples of white glutinous rice and black glutinous rice were grouped in various proportional ratios. Different pre-cooking preparation techniques and cooking methods were performed for each group. Ethanolic extraction was used for all cooked glutinous rice samples and the supernatant was collected for analysis. The results showed that a high ratio of black glutinous rice yielded a high bioactive compound content (phenolics, flavonoids, and anthocyanins), and a relatively high percentage for inhibition of key enzyme activity (α-amylase and α-glucosidase). The sample consisting solely of white glutinous rice showed the lowest values of all samples. Samples prepared with hot water and cooked using a steamer had a relatively high bioactive compound content and a high percentage of key enzyme inhibitory activity. This study has determined the cooking processes that best preserve the bioactive compounds found in black glutinous rice which performed with hot water pre-cooking preparation and steamer technique. The factors also stimulate active compounds that inhibit key digestive enzyme activity. Therefore, these results provide preliminary evidence to support the development of health promotion guidance for regular consumers of glutinous rice.