Enthalpy relaxation of gelatin in the glassy state

Badii, Fojan; MacNaughtan, William; Farhat, Imad A.

doi:10.1016/j.ijbiomac.2005.06.008

Cited by 45 publications

(28 citation statements)

References 32 publications

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“…These DSC features have been described for various materials and theoretically simulated, as characteristic of the phenomenon of structure/enthalpy relaxation commonly referred to as "physical ageing" [37][38][39] . Several studies [27][28][29] showed that the magnitude of the overshoot or the difference in energy between aged and non-aged samples was a quantitative measure of the structure relaxation that had occurred during ageing; but the reason for a possible exothermic event is not clear and will require further study. In any event, it is clear that the state of the substrate is significantly different at each stage of the absorption experiment.…”

Section: Sorption Samplesmentioning

confidence: 99%

“…Moreover, the glass transition is not an absolute barrier to molecular mobility. Whilst glass formation certainly slows some kinetic events in the system, it is now understood that glasses containing plasticiser are not stable, and can age during the slow processes of drying, rehydration and storage [25][26][27][28][29] . This ageing is only reversed by heating above the glass transition, or by adding sufficient plasticiser so that the system is above the transition temperature under ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

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Structural Relaxation During Drying and Rehydration of Food Materials—the Water Effect and the Origin of Hysteresis

et al. 2011

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The state of water in foodstuffs is a guiding principle in food design, and the equilibrium concept of water activity (Aw) is ubiquitous. It is regarded as a primary variable or "hurdle" in preservation technology, and a key variable influencing chemical reaction during storage. However, the amount of water in any system differs as function of water activity depending whether it is determined by water sorption or desorption. Even though this hysteresis behaviour has already been described in the literature, no physical interpretation of its origin has yet been proposed with respect to detailed molecular organisation. This work shows, for two different food powders, gluten and a milk-based product that the hysteresis disappears when either go through their glass transition. A more complete DSC analysis for gluten during different sorption/desorption cycles demonstrates that the hysteresis is dependent on the ageing of the material, which evolves in the glassy state and is induced by structural relaxation.

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Section: Sorption Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structural Relaxation During Drying and Rehydration of Food Materials—the Water Effect and the Origin of Hysteresis

et al. 2011

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“…1 Amorphous glassy materials are thermodynamically unstable, and during storage their structures tend to relax toward the equilibrium state. [2][3][4][5] Consequently, the enthalpy and volume of a glassy material decrease over time; this phenomenon is often referred to as physical aging. 6 It has been observed that increasing the aging temperature to a sufficiently high temperature below T g , increases the magnitude of the relaxation endotherms observed by DSC.…”

Section: Introductionmentioning

confidence: 99%

“…6 It has been observed that increasing the aging temperature to a sufficiently high temperature below T g , increases the magnitude of the relaxation endotherms observed by DSC. 2,5,7 Many studies have been reported on enthalpy relaxation in synthetic polymers. 6,[8][9][10][11] Some macroscopic properties, such as density, mechanical strength, and vapor permeability can be affected by enthalpy relaxation in amorphous glassy materials.…”

Section: Introductionmentioning

confidence: 99%

Glass transition and enthalpy relaxation of amorphous lactose glass

Haque

Kawai

Suzuki

2006

Carbohydrate Research

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“…The endotherm was reversible with time and reappeared after 15 h of storage at Tg−15 ( Figure 4a). This feature attributed to a structural relaxation frequently observed on biopolymers 23,[45][46][47] reflects the enthalpy changes induced by structural rearrangements of the glassy material upon storage. The relaxation enthalpy of the blends equilibrated at 66% RH aged at Ta=Tg−15 kept increasing even after 668 h, suggesting that more enthalpy and free volume (provided that the relaxation kinetics of enthalpy and specific volume are similar) should be relaxed before equilibrium could be reached.…”

Section: Study Of Molecular Mobility In Glassy Materialsmentioning

confidence: 79%

Low-Moisture Food: A Physicochemical Approach to Investigate the Origin of Their Physical Instability versus Water or Sucrose

Roudaut

Champion

2011

Food Biophysics

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Low-moisture biopolymer-based systems are commonly encountered in food. Obviously, understanding the physical basis of their quality [texture, or performance over time or as a function of their composition (water or other added solutes)] is of primary importance. A polymer science approach using physical chemistry concepts based on physical state, phase transitions and molecular mobility can be applied to investigate the performances of food in particular versus moisture. Based on the example of starchbased samples and their texture property changes versus composition, the role of water and sucrose is considered through different aspects. The relations existing between the observed changes and physical state are investigated. While the motions associated with the glass transition were observed at high temperature, secondary relaxations are observed below Tg (at T β ): T β decreased with water content and increased with increasing sucrose content. These local motions are suggested to contribute to the observed texture modifications versus water. Moreover, the stability of the glassy state was investigated by differential scanning calorimetry through the study of enthalpy relaxation (physical ageing). The amplitude of enthalpy relaxation decreased with both increasing sucrose and water content. All in all, this study strengthened the hypotheses that subTg mobility could contribute to texture instability versus moisture or sugar content.

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Enthalpy relaxation of gelatin in the glassy state

Cited by 45 publications

References 32 publications

Structural Relaxation During Drying and Rehydration of Food Materials—the Water Effect and the Origin of Hysteresis

Structural Relaxation During Drying and Rehydration of Food Materials—the Water Effect and the Origin of Hysteresis

Glass transition and enthalpy relaxation of amorphous lactose glass

Low-Moisture Food: A Physicochemical Approach to Investigate the Origin of Their Physical Instability versus Water or Sucrose

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