Freeze state diagram

Figure 5.4. A schematic state diagram showing water plasticization at increasing water weight fraction towards glass transition of water at -135°C. Relaxation times decrease rapidly above the glass transition as a result of thermal or water plasticization. Maximally freeze-concentrated solutes show glass transition at Tg and onset of ice melting at TJ. Equilibrium melting is described by the T curve.

Figure 5.5. State diagram of sucrose with typical experimental data at high concentrations and in the maximally freeze-concentrated state. Dynamic mechanical and dielectric measurements show glass transition-related relaxations.

Figure 7.3 is another example of a typical state diagram, developed for maltose. Maltose solutions are in glassy state below Tg curve. T g (onset of glass transition) and (onset of ice melting) show constant values for the maximally freeze concentrated solutions, where maximum ice formation occurs between T and Tg, and T is at the end point region of Tg (Figure 7.3) (Roos and Karel 1991b). State diagram for sucrose (Figure 7.4) also shows similar characteristics (Roos and Karel 1991a).

Figure 7.27. Location of various food processes, ineluding freezing, dehydration, heating and cooling, on a state diagram (Reproduced with permission from Effeets of glass transition on processing and storage by Karel, Buera, and Roos (In The Glassy State in Foods, Blanshard and Lillford (Eds.)), 1993, Nottingham University Press.)...

For simple adsorbates composed of spherical molecules in pores of simple geometry, it is possible to map out freezing phase diagrams based on the simulation studies [3,6]. A corresponding states analysis [3] of the partition function for such a system shows that the freezing temperature in the pore, 7/pore, relative to the value for the bulk material, Tfbutk, is a function of three variables H/aff, a, and Ofjoff, where H is pore width, CT is the molecular diameter, subscripts / and w refer to fluid and wall, respectively. 

FIGURE 8.11 State diagram for food materials, showing the Tg curve and isoviscous states above Tg. Maximally freeze-concentrated solids with a solute concentration of C g have Tg at T g. Ice melting within maximally freeze-concentrated materials occurs at T m. The equilibrium melting curve shows the equilibrium melting point Tm as a function of concentration. (From Roos, Y.H. and Karel, M., Food Technol., 45, 66, 1991b.)... 

Schematic state diagram at constant pressure of an aqueous binary solution showing the equilibrium freezing curve, the solubility line, and the glass transition temperatures.

State Diagram for Freeze-Dried Plum and Glass Transitions of Plum Skin and Pulp... 

The objective of this work was to study the state transitions of freeze-dried plum and to draw the corresponding state diagram for this material. Class transitions of separated plum skin and pulp were also investigated, aiming to clarify the effect of each of these fractions on the behavior of the whole fruit. 

State diagram of freeze-dried plum (skin/pulp at the natural proportion) ( , First T A, T X, I m +, Second Tg). 

A state diagram for freeze-dried plum was obtained and the Gordon-Taylor model could adequately represent the sugar matrix glass-transition curve. 

Bai, Y., Shafiur Rahman, M., Perera, C.O., Smith, B., and Melton, L.D. State diagram of apple slices glass transition and freezing curves. Food Res. Int., 34, 89, 2001. 

Telis, V.R.N. and Sobral, P.J.A. Glass transitions and state diagram for freeze-dried pineapple, Lebensm.-Wiss. Technol., 34, 199, 2001. 

FIGURE 16.6 State diagram of the sucrose-water system. T is temperature, ij/s mass fraction of sucrose. Tf gives the freezing temperature of water and Ts the solubility of sucrose. Tg is the glass transition temperature and Thom the homogeneous nucleation temperature. 

FIGURE 1.5 State diagram of foods boiling point T, eutectic point T, end of freezing T, glass tran-... 

Figure 11.5 State diagram for an aqueous sugar solution and typical freeze-drying curve...

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