Effect of Glass Transition Temperature Range on the Caking Behavior of Freeze-dried Carbohydrate Blend Powders
- PDF / 768,052 Bytes
- 11 Pages / 595.276 x 790.866 pts Page_size
- 81 Downloads / 246 Views
Effect of Glass Transition Temperature Range on the Caking Behavior of Freeze-dried Carbohydrate Blend Powders Alex Eduardo Alvino Granados 1 & Takumi Mochizuki 1 & Kiyoshi Kawai 1,2 Received: 14 November 2019 / Accepted: 11 May 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Glass transition temperature (Tg) and degree of caking for maltodextrin with added plasticizers (glucose, maltose, and sorbitol) were investigated. Onset and offset Tgs were evaluated by differential scanning calorimetry. From the onset and offset Tg-curves and water sorption isotherm, each critical water activity (awc) value was determined (water activity at each Tg = 25 °C). The awc range between onset Tg and offset Tg was extended by the addition of plasticizers. The degree of caking increased at a water activity just above awc of onset Tg, and completely caked at a water activity just below awc of offset Tg. Effect of aw on the degree of caking became more gradual with the addition of plasticizers because of the extended awc range. According to the dependence of viscosity on temperature and water activity, a predictive model for the caking of amorphous powders was proposed based on the onset and offset Tg curves. Keywords Glass transition temperature . Water sorption isotherm . Mechanical relaxation . Caking . Viscosity
Introduction Amorphous food powders show glass-to-rubber transition (glass transition) upon changes in temperature and water content. Glass transition is characterized by the glass transition temperature (Tg) [1]. Glassy amorphous powders (T < Tg) have a solid-like property based on the extremely low molecular mobility and/or high viscosity [2]. Thus, physical stability is expected for the amorphous powder, and caking [3] and re-crystallization [4] are prevented. Rubbery amorphous powders (T > Tg), on the other hand, have a liquid-like property, and physical deteriorations may occur depending on the storage time. Since the Tg of amorphous food powders decreases with an increase in water content, glass transition is caused by water sorption Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12393-020-09226-z) contains supplementary material, which is available to authorized users. * Kiyoshi Kawai [email protected] 1
Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan
2
Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan
even at a constant temperature; when the Tg becomes lower than ambient temperature (typically 25 °C) as a result of water sorption, the glassy material changes to a rubbery material. The effect of water content on Tg has been described as the Tg curve. From the Tg curve, the water content at Tg = 25 °C can be determined as critical water content (wc) [5]. In addition, wc is converted to critical water activity (awc) through the effect of water activity (aw) on the equil
Data Loading...
