Physical aging of glassy normal and waxy rice starches: Effect of aging time on glass transition and enthalpy relaxation

Hyun Jung Chung, Seung Taik Lim

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Physical aging and glass transition characteristics of amorphous normal and waxy rice starches (11 and 15% moisture contents) were investigated under differential scanning calorimetry as function of aging time. Normal rice starch showed higher Tg than waxy rice starch. The Tg and ΔCp at glass transition gradually increased with aging time, whereas fictive temperature was slightly reduced regardless of moisture content and starch type. The relaxation enthalpy and relaxation peak temperature increased with aging time until structural equilibrium was reached. Enthalpy increase was more significant in the early stage of aging whereas temperature increase was constant during the aging period tested (120 h). Aging kinetic analysis using Cowie and Ferguson model revealed that the amorphous normal and waxy rice starches behaved in different modes for the physical aging. Relaxation distribution parameter (β) of both starches was in a range of 0.3 < β < 0.7, but higher at a lower moisture content, and for normal starch than for waxy starch. Maximum relaxation enthalpy for normal starch (1.10 and 2.69 J/g, respectively, at 11 and 15% moistures) was higher than those of waxy starch (0.77 and 2.48 J/g). Based on the characteristic time (tc), normal starch has slower progression toward an equilibrium than waxy starch. Overall results proved that physical aging kinetics were highly dependent on starch structure and composition.

Original languageEnglish
Pages (from-to)855-861
Number of pages7
JournalFood Hydrocolloids
Volume17
Issue number6
DOIs
Publication statusPublished - 2003 Nov 1

Keywords

  • Enthalpy relaxation
  • Glass transition
  • Physical aging
  • Rice starch

ASJC Scopus subject areas

  • Food Science

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