Thermal characteristics, chemical composition and polyphenol contents of date-pits powder

Sithara Suresh, Nejib Guizani, Mohamed Al-Ruzeiki, Ahlam Al-Hadhrami, Halima Al-Dohani, Issa Al-Kindi, Mohammad Shafiur Rahman

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Polyphenol contents in date-pits varied from 21-62 mg gallic acid equivalents (GAE)/g date-pits when acetone-water, ethanol-water, methanol-water and water alone were used as solvents for extraction at temperatures 22, 45, and 60 C. The BET and GAB monolayer values of date-pits were estimated as 4.3 and 4.1 g/100 g dry-solids. The DSC thermogram of freeze-dried date-pits showed an endothermic peak due to the melting of oil, and a second endothermic peak for solids-melting (i.e. non-fat). The first shift indicated the glass transition (i.e. Tg) while the second exothermic shift after solids-melting indicated the interactions of the components in melted solids. The melting peak temperature was decreased due to the plasticization of solids with water and the melting enthalpy was increased with the increasing water content due to the formation of more order in the amorphous, semi-crystallites and crystallites parts. The Flory-Huggins modelling of peak temperature estimated the water-solids interaction parameter as 0.0068. The melting peak temperature increased exponentially with increasing heating rate and the data was fitted with Mehl-Johnson-Avrami and Kissinger models. Annealing close to the onset of melting indicated that melting peak temperature increased exponentially with increasing annealing time, while melting enthalpy decreased with the increasing annealing time.

Original languageEnglish
Pages (from-to)668-679
Number of pages12
JournalJournal of Food Engineering
Volume119
Issue number3
DOIs
Publication statusPublished - 2013

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Keywords

  • Annealing
  • Date-pits
  • DSC
  • Glass transition
  • Melting kinetics
  • Total polyphenol

ASJC Scopus subject areas

  • Food Science

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