Study on the factors affecting starch digestibility of rice flour based products and instant rice
Date Issued
2015
Date
2015
Author(s)
Hsu, Rachel Jui-cheng
Abstract
Rice being the staple food in Taiwan and Asia is the main source of carbohydrate in many countries. The nutritionally important fractions of food starches can be classified as rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) based on the rate of digestion according to Englyst’s assay. RDS content of starchy food is positively correlated to glycemic response. Oppositely, starchy food containing higher content of SDS leads to less glycemic response and makes it more nutritional for reducing the risk of raising glycemic response. In this study, we aimed to evaluate optimum process conditions for rice flour based foods and instant rice for reducing starch digestibility from domestic rice varieties. The results showed that the amount of water added for cooking and extending refrigeration duration impacted majorly on the starch digestibility of both low-amylose and high amylose for rice flours. By properly selecting a lower temperature, comparing to the traditional electronic cooker, with minimum time as well as adding limited water significantly reduced RDS of cooked rice. Evidence of SEM photogram showed that lower temperature cooking made the starch gelatinized without disruption all starch granule, leading to the lower starch digestibility. One day refrigeration was enough for the conformation of starch structure. The synergy of refrigeration and lower temperature drying significantly reduced the starch digestibility. In addition, molecular structure of rice starch significantly not only affected the starch digestibility of rice flour based products, but also the rehydrated instant rice. It appears possible to reduce rice starch digestibility by establishing optimum processing conditions for different rice varieties.
Subjects
rice
rice flour
instant rice
starch digestibility
rice based products
Type
thesis
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