Study on isolation and digestibility of Vietnamese rice starches

Abstract

The resistant starch is known as a beneficial carbohydrate especially in colonic health and glycemic control. Therefore, this study aimed to investigate digestibility of ten popular Vietnamese rice starches as well as improve resistant starch in several rice starches. The rice starches were isolated from rice flour by neutral protease digestion method and then analyzed to determine the chemical compositions such as moisture, ash, protein, lipid and amylose contents. Three starch fractions including rapidly digestible starch (RDS), slowly digestible Starch (SDS) and resistant Starch (RS) of ten rice starch samples were measured. In all rice starches, the RDS fraction is the highest (67.15-74.92%), followed by SDS (13.36-23.76%) and RS (9-13.18%), respectively. Furthermore, three rice starches which have different levels of amylose contents were treated by Pullulanase in 24 hours, then they were stored at three temperature (room temperature, 4oC and - 18oC) before drying. The content of RS increased significantly after treatment. RS

content increased from 12.82% to 20.13, 25.16 and 27.38% in NCHV, from

10.42% to 17.32, 22.63 and 23.59% in BH, from 9.13% to 13.84, 18.38 and

21.02% in HL, when stored at RT, 4oC and -18oC, respectively. Thus, debranched rice starches can be applied in food technology as a valuable added ingredient or functional food.

Keywords: rice starch, digestibility, rapidly digestible starch, slowly digestible starch, resistant starch.