Fat oxidation in freeze-dried grouper during storage at different temperatures and moisture contents

Mohammad Shafiur Rahman, Ruqaya Moosa Al-Belushi, Nejib Guizani, Ghalib Said Al-Saidi, Bassam Soussi

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41 Citations (Scopus)

Abstract

The effects of moisture content levels and storage temperature on the lipid oxidation in freeze-dried grouper were studied. Three trends were observed in the changes of PV (peroxide value) depending on the moisture content and storage temperature. An exponential rise of PV was observed (p <0.05) at lower temperatures (-20 °C and 5 °C for samples at moisture 5 g/100 g; and -20 °C for samples at moisture 20 g/100 g). At temperatures 25 °C for samples at moisture 5 g /100 g, and 5 and 25 °C for samples at 20 g moisture/100 g peaks of PV were observed (p <0.05). At higher temperatures (40 °C for both moisture content levels) an exponential decay instead of increase were observed (p <0.05). Moisture content levels had no significant effect (p > 0.05) on PV stored at temperature of -40 °C. The monolayer moisture for freeze-dried grouper was estimated as 6.2 g/100 g dry solids using BET-isotherm. Differential scanning calorimetry (DSC and modulated DSC) thermogram line showed two shifts (i.e. glass transition) and two endothermic peaks, one for melting of oil and another for decomposition. The validity of the water activity and glass transition concepts were evaluated. It is concluded that glass transition concept may be used to explain the process more adequately.

Original languageEnglish
Pages (from-to)1257-1264
Number of pages8
JournalFood Chemistry
Volume114
Issue number4
DOIs
Publication statusPublished - Jun 15 2009

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Keywords

  • Differential scanning calorimetry (DSC)
  • Glass transition
  • Moisture isotherm
  • Plasticisation
  • State diagram

ASJC Scopus subject areas

  • Food Science
  • Analytical Chemistry

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