Preprint Article Version 1 This version is not peer-reviewed

Using Dielectric Relaxation Spectroscopy to Characterize the Glass Transition and Onset of Crystallinity of Skim-Milk Powder

Version 1 : Received: 9 April 2018 / Approved: 9 April 2018 / Online: 9 April 2018 (10:22:24 CEST)

How to cite: Buehler, M.G. Using Dielectric Relaxation Spectroscopy to Characterize the Glass Transition and Onset of Crystallinity of Skim-Milk Powder. Preprints 2018, 2018040105 (doi: 10.20944/preprints201804.0105.v1). Buehler, M.G. Using Dielectric Relaxation Spectroscopy to Characterize the Glass Transition and Onset of Crystallinity of Skim-Milk Powder. Preprints 2018, 2018040105 (doi: 10.20944/preprints201804.0105.v1).

Abstract

This paper describes the dielectric relaxation spectroscopy (DRS) method for obtaining glass transition temperature and the onset of crystallinity of skim milk powder (SMP). The methodology consists of exposing SMP samples to numerous constant temperatures, T, and water activities, aw, and measuring the relaxation time. Measurements are based on changes in the loss-tangent height at its peak frequency. Glass transition times are identified at peaks in the loss-tangent height versus time curve and the onset of crystallinity times are identified when the loss-tangent height collapses. The analysis leads to two boundary curves: glass transition Tg, aw curve and the onset of crystallinity Tc, aw curve. They separate the SMP stable (long shelf life) and unstable (short shelf life) regions. Two curve fitting algorithms were developed for (a) aw2, tg curve where tg is the time to glass transition and aw2, tc curve where time tc is the time to onset of crystallinity and (b) Tg, aw and Tc, aw boundary curves. Finally, the DRS data are compared to differential scanning calorimetry (DSC) results.

Subject Areas

DRS dielectric relaxation; DSC differential scanning calorimetry; SMP skim milk powder; boundary curves

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