Glass Transition of Pomegranate Skin, as Analyzed by Thermal, Mechanical, and Nuclear Magnetic Resonance Methods

Mohammad Shafiur Rahman, Amani Al-Rawahi

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Glass transition of pomegranate skin was measured by thermal, mechanical, and magnetic resonance techniques. Differential scanning calorimetry thermogram showed a shift (i.e., onset glass transition at 20°C) followed by an endothermic peak (i.e., solids-melting peak at 165°C and enthalpy 140 kJ/kg). Overlapping of the glass transition and melting was observed in the differential scanning calorimetry thermogram; however, more sensitive modulated differential scanning calorimetry allowed to separate two transitions (i.e., glass transition from reversible and melting from non-reversible thermograms). The onset of mechanical glass-rubber transition from differential mechanical thermal analysis was observed at 122°C with a shift in the storage modulus (E′); however, the onset of liquid-like or entangled-reaction dominating transition was observed at 70°C (i.e., onset peak in loss modulus, E′′) and peak at 184°C. In addition onset peak in tan δ was observed at 113°C and peak at 201°C. Spin–spin (T2 relaxation) and spin-lattice (T1 relaxation) relaxations in time domain nuclear magnetic resonance was modeled by two-exponential relaxation curve (i.e., rigid and flexible domains). T2 relaxation showed maximum peak with an onset at 40°C with maximum peak at 150°C. Rigid domain of T1 relaxation showed a minimum peak onset at 40°C and a minimum peak at 120°C, whereas flexible component showed an onset at 20°C and a minimum peak at 160°C.

Original languageEnglish
Pages (from-to)1-13
Number of pages13
JournalInternational Journal of Food Properties
DOIs
Publication statusAccepted/In press - Sep 21 2016

Keywords

  • Glass transition
  • Relaxation
  • Solids-melting
  • Stability
  • Thermal characteristics

ASJC Scopus subject areas

  • Food Science

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