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Trends in Applied Sciences Research

Year: 2007 | Volume: 2 | Issue: 3 | Page No.: 175-187
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Authors

Vasudeva Singh

Seiichiro Isobe

Hidechika Toyoshima

Hiroshi Okadome

Ken`ichi Ohtsubo

Keywords

Starches from three varieties of rice of high amylose (indica), intermediate amylose (japonica) and almost negligible amylose (japonica waxy) were isolated. They were acetylated by using four times their weight of acetic anhydride (11% sodium hydroxide as 50% aqueous solution as catalyst) for 15, 30 and 60 min.The acetyl content varied from 30 to 41% and degree of substitution (DS) from 1.63 to 2.55. Under similar conditions of acetylation, waxy rice starch showed highest acetyl content and highest DS. Dimethyl formamide was the solvent used for dispersing these modified starches. Films of indica modified starch of 30% acetyl content and 1.63 DS showed highest strength compared to other varieties of modified starch. Glass transition temperature (Tg) was highest in waxy rice starch (~ 232°C) followed by japonica non-waxy and indica rice starch. After acetylation, the Tg values increased in waxy modified ones, remained almost same in indica modified ones, decreased to some extent in japonica non-waxy modified ones compared to their respective native starches. Difference in specific heat capacity between starting and ending of glass transition point of indica and its modified ones remained almost same, increased in japonica and its derivatized ones, decreased in waxy modified one compared to their respective native starches. Among the native starches, melting point was highest in waxy starch. Modification increased this property in all the starches under all periods of acetylation. Increment was highest in japonica waxy acetylated ones. Degradation or decomposition of these starches occurred at 3-10°C higher than their respective melting points. Heat evolution was very high in japonica native (~ 203 mJ mg-1) and heat absorption was highest in indica 15 min modified one (~ 265 mJ mg-1). Difficulties encountered while determining the dynamic viscosity using the equipment of the synthetic polymer have been explained.
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How to cite this article

Vasudeva Singh, Seiichiro Isobe, Hidechika Toyoshima, Hiroshi Okadome and Ken`ichi Ohtsubo, 2007. Preparation and Properties of High Degree Substituted Acetylated Rice Starches and Preparation of Their Films Part 1 . Trends in Applied Sciences Research, 2: 175-187.

URL: https://scialert.net/abstract/?doi=tasr.2007.175.187

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