State diagram of apple slices: glass transition and freezing curves

Differential scanning calorimetry (DSC) was used to determine phase transitions of freeze-dried plums. Samples at low and intermediate moisture contents, were conditioned by adsorption at various water activities (0.11≤aw≤0.90) at 25°C, whereas in the high moisture content region (aw>0.90) samples were obtained by direct water addition, with the resulting sorption isotherm being well described by the Guggenheim-Anderson-deBoer (GAB) model. Freeze-dried samples of separated plum skin and pulp were also analysed. At aw≤0.75, two glass transitions were visible, with the glass transition temperature (Tg) decreasing with increasing aw due to the water plasticising effect. The first Tg was attributed to the matrix formed by sugars and water. The second one, less visible and less plasticised by water, was probably due to macromolecules of the fruit pulp. The Gordon-Taylor model represented satisfactorily the matrix glass transition curve for aw≤0.90. In the higher moisture content range Tg remained practically constant around Tg′ (−57.5°C). Analysis of the glass transition curve and the sorption isotherm indicated that stability at a temperature of 25°C, would be attained by freeze dried plum at a water activity of 0.04, corresponding to a moisture content of 12.9% (dry basis).

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State Diagrams of Two Thai Rice Varieties Differing in Amylose Contents

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.848.89 ◽

2016 ◽

Vol 848 ◽

pp. 89-94

Author(s):

Chutamas Boonrod ◽

Khongsak Srikaeo

Keyword(s):

Glass Transition ◽

Freezing Point ◽

Amylose Content ◽

State Diagram ◽

The State ◽

Published Data ◽

Rice Varieties ◽

State Diagrams ◽

Physicochemical Changes ◽

Solids Content

State diagram is a map of the different states of a food polymer as a function of water or solids content and temperature. The main advantage of drawing map is in identifying different states of a food polymer which helps in understanding the complex changes when food's water content and temperature are changed. It also assists in identifying food’s stability during storage as well as selecting suitable conditions for processing. This research successfully developed the state diagrams of two Thai rice varieties differing in amylose contents (San-pah-tawng and Phitsanulok 2) by measuring the glass line; glass transition temperature (Tg) vs. solids content, freezing curve; initial freezing point vs. solids content by using the differential scanning calorimetry (DSC) method. Rice with different amylose content exhibited similar freezing curves and glass transition patterns. The state diagrams obtained in this study are in agreement with previously published data. They can be useful in optimizing the drying and freezing processes as well as studying the physicochemical changes during storage of rice.

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Glass transition and state diagram for fresh and freeze-dried Chinese gooseberry

Journal of Food Engineering ◽

10.1016/j.jfoodeng.2007.05.024 ◽

2008 ◽

Vol 84 (2) ◽

pp. 307-312 ◽

Cited By ~ 53

Author(s):

Haiying Wang ◽

Shaozhi Zhang ◽

Guangming Chen

Keyword(s):

Glass Transition ◽

State Diagram ◽

Freeze Dried

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State diagram of dates: Glass transition, freezing curve and maximal-freeze-concentration condition

Journal of Food Engineering ◽

10.1016/j.jfoodeng.2010.02.003 ◽

2010 ◽

Vol 99 (1) ◽

pp. 92-97 ◽

Cited By ~ 56

Author(s):

Nejib Guizani ◽

Ghalib Said Al-Saidi ◽

Mohammad Shafiur Rahman ◽

Salwa Bornaz ◽

Ahmed Ali Al-Alawi

Keyword(s):

Glass Transition ◽

State Diagram ◽

Freeze Concentration ◽

Freezing Curve ◽

Concentration Condition

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Modeling of atmospheric freeze-drying for sliced fruit

Proceedings of 21th International Drying Symposium ◽

10.4995/ids2018.2018.7643 ◽

2018 ◽

Author(s):

Kyuya Nakagawa ◽

Akane Horie ◽

Takashi Kobayashi

Keyword(s):

Mathematical Model ◽

Glass Transition ◽

Vapor Pressure ◽

Heat Balance ◽

Freeze Drying ◽

Glassy State ◽

Glassy Matrix ◽

Reasonable Accuracy ◽

Balance Equations ◽

Apple Slices

A mathematical model that simulates atmospheric freeze-drying for apple slices was developed based on the classical mass and heat balance equations. When operated above the glass transition temperature, product shrinkage and micro-collapse due to the glass-rubber transition occurred. So, instead of assuming formation of dried and frozen zones, a glassy matrix with particular vapor pressure was assumed. Apparent vapor pressure of apple slices in the glassy state was experimentally measured and summarized in a diagram, and the values in this diagram were employed for the simulation. This approach well predicted drying kinetics with reasonable accuracy with simplified equations. Keywords: atmospheric freeze-drying; food; mathematical model; glassy state

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