TY - JOUR
T1 - Rheology of carbohydrate blends close to the glass transition
T2 - Temperature and water content dependence of the viscosity in relation to fragility and strength
AU - Ubbink, Job
AU - Dupas-Langlet, Marina
N1 - Publisher Copyright:
© 2020
PY - 2020/12
Y1 - 2020/12
N2 - Several modifications of the Williams-Landel-Ferry (WLF) equation that incorporate the water-content dependence of the viscosity are introduced and applied to the fitting the zero-shear viscosity of a systematic series of maltopolymer-maltose blends for water contents w between 4% and 70% (M. Dupas-Langlet et al., Carbohydrate Polymers 213 (2019) 147–158). These models include a previously published model that addresses the water-content dependence of the viscosity via a Gordon-Taylor-type modification of the C2 coefficient of the WLF equation. New models that are based on two simple assumptions are introduced: 1. The viscosity at the glass transition temperature Tg decreases exponentially with the water content and 2. The WLF coefficient C2 depends linearly on the water content. The modified WLF models allow to extract the so-called isoviscosity lines, that connect points of varying temperature and water content that are characterized by the same viscosity. Based on data obtained between T = −15 °C and 70 °C using shear rheology (w = 30–70% w/w) and dynamic mechanical thermal analysis (w = 4–9% w/w), we conclude that the models provide a good fit of the experimental data, and that additional data, specifically very close to the glass transition line, is needed, to assess the hypotheses underlying the various modified WLF models. It is established that the viscosity at Tg is dependent on the composition and decreases with the content of maltose and water. The modified WLF models are used to determine Angell's fragility parameter m and Roos’ strength parameter S. m and S are observed to increase, respectively decrease with increasing water and maltose content, signifying an increasing temperature dependence of the viscosity close to Tg with decreasing diluent content. The application of the isoviscosity concept to unit operations in the food and pharmaceutical industry is discussed. Specifically, we show how to analyze atomization, agglomeration, sintering and compaction using the isoviscosity concept.
AB - Several modifications of the Williams-Landel-Ferry (WLF) equation that incorporate the water-content dependence of the viscosity are introduced and applied to the fitting the zero-shear viscosity of a systematic series of maltopolymer-maltose blends for water contents w between 4% and 70% (M. Dupas-Langlet et al., Carbohydrate Polymers 213 (2019) 147–158). These models include a previously published model that addresses the water-content dependence of the viscosity via a Gordon-Taylor-type modification of the C2 coefficient of the WLF equation. New models that are based on two simple assumptions are introduced: 1. The viscosity at the glass transition temperature Tg decreases exponentially with the water content and 2. The WLF coefficient C2 depends linearly on the water content. The modified WLF models allow to extract the so-called isoviscosity lines, that connect points of varying temperature and water content that are characterized by the same viscosity. Based on data obtained between T = −15 °C and 70 °C using shear rheology (w = 30–70% w/w) and dynamic mechanical thermal analysis (w = 4–9% w/w), we conclude that the models provide a good fit of the experimental data, and that additional data, specifically very close to the glass transition line, is needed, to assess the hypotheses underlying the various modified WLF models. It is established that the viscosity at Tg is dependent on the composition and decreases with the content of maltose and water. The modified WLF models are used to determine Angell's fragility parameter m and Roos’ strength parameter S. m and S are observed to increase, respectively decrease with increasing water and maltose content, signifying an increasing temperature dependence of the viscosity close to Tg with decreasing diluent content. The application of the isoviscosity concept to unit operations in the food and pharmaceutical industry is discussed. Specifically, we show how to analyze atomization, agglomeration, sintering and compaction using the isoviscosity concept.
KW - Agglomeration
KW - Collapse
KW - Differential scanning calorimetry (DSC)
KW - Dynamic mechanical thermal analysis (DMTA)
KW - Food powder
KW - Glass transition
KW - Plasticization
KW - Sintering
KW - Spray drying
KW - State diagram
KW - Sticky line
KW - WLF equation
KW - Water
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U2 - 10.1016/j.foodres.2020.109801
DO - 10.1016/j.foodres.2020.109801
M3 - Article
C2 - 33288183
AN - SCOPUS:85093649312
SN - 0963-9969
VL - 138
JO - Food Research International
JF - Food Research International
M1 - 109801
ER -