Rice starch vs. rice flour: Differences in their properties when modified by heat–moisture treatment

• Published in: Carbohydrate polymers 2013-01, Vol.91 (1), p.85-91
• Main Authors: Puncha-arnon, Santhanee, Uttapap, Dudsadee
• Format: Article
• Language: English
• Subjects: Flour; Food Handling - methods; gelatinization; Gels; hardness; Heat–moisture treatment; Hot Temperature; Oryza - chemistry; Pasting properties; Plant Proteins - analysis; proteins; rice; Rice flour; Rice starch; Starch - chemistry; starch granules; thermal properties; viscosity; water content
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2012.08.006

► Heat–moisture treatment (HMT) of rice starch and rice flour was studied. ► HMT had a much greater effect on the paste viscosity of flour than that of starch. ► HMT had stronger effects on gel and thermal properties of rice flour. ► Removal of protein from HMT flours resulted in higher paste viscosity. ► Protein played an important role in affecting properties of HMT products. Starch and flour from the same rice grain source (with 20, 25 and 30% moisture content) were exposed to heat–moisture treatment (HMT) at 100°C for 16h in order to investigate whether there were differences in their susceptibility to modification by HMT and, if any, to determine the main causes of the differences. HMT had a far greater effect on paste viscosity of flour than of starch. A significant increase in paste viscosity after removal of proteins from HMT flour – as well as images of fast green-stained HMT flour gels – indicated that an important role was played by proteins in affecting properties of the modified samples. Greater effects of HMT on thermal parameters of gelatinization and gel hardness values of flours were observed – more so than those for starches. Following this observation, it was ascertained that components in rice flour other than rice starch granules also underwent alterations during HMT.