Exploring validity of the macro-micro region concept in the state diagram: Browning of raw and freeze-dried banana slices as a function of moisture content and storage temperature

Mohammad Shafiur Rahman, Ghalib Said Al-Saidi

Research output: Contribution to journalArticle

7 Citations (Scopus)


State diagram (i.e. 12 micro-regions) of ripe banana was mapped by measuring and modeling its freezing point, glass transition, maximal-freeze-concentration conditions, solids-melting, and BET-monolayer. At 20 °C, the BET-monolayer moisture was observed as 0.044 g/g dry-solids, and decreased with the increase of temperature. Un-freezable water was found as 0.26 g/g sample and the maximal-freeze-concentration temperature (Tm′) was observed as −34.5 °C. The freezing point and solids-melting peak were modeled by Chen's and Flory-Huggins models, respectively. Browning of banana stored at different moisture and temperature (i.e. at different micro-regions) were measured as a function of storage time and modeled with first order reaction kinetics. The variation of reaction rate constant was analyzed based on the glass transition, water activity and macro-micro region concepts. At a specific moisture content, reaction rate constant showed a shift (i.e. sample containing freezable water) or change in slope (i.e. sample containing un-freezable water), when plotted as a function of temperature. However, it was difficult to find any validity above or below glass transition (or BET-monolayer) when all data points (i.e. all moisture and temperature) were plotted (i.e. rate constant with moisture or temperature). Arrhenius plot at moisture content 0.04 g/g sample showed two linear regions (i.e. below and above critical temperature 45 °C) with activation energy values of 105.3 and 25.1 kJ/mol, respectively. Universal validation was difficult to achieve, thus the rate constants within different micro-regions were empirically correlated with moisture content, storage temperature, BET-monolayer and glass transition temperature (p < 0.001).

Original languageEnglish
Pages (from-to)32-40
Number of pages9
JournalJournal of Food Engineering
Publication statusPublished - Jun 1 2017



  • Activation energy
  • Browning
  • Glass transition
  • Molecular mobility
  • Reaction kinetics
  • Water activity

ASJC Scopus subject areas

  • Food Science

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