Physical Chemistry of Foods
changes can reinforce other instabilities: an increase in particle size leads to enhanced sedimentation, and coalescence of flui ...
important one is that the liquid shows Newtonian behavior. Many liquids (e.g., most polymer solutions) are markedly strain rate– ...
globules. It will then be wetted by oil from the other globule, and oil–oil contact is made, without full coalescence occurring. ...
Question A food company makes a product that is an oil-in-water emulsion. To check on its physical stability, a sample of each d ...
Especially Chapters 1 by B. P. Binks (introduction), 7 by A. S. Kabalnov (coalescence), and 9 by J. G. Weers (Ostwald ripening a ...
14 Nucleation When the temperature, the pressure, or the solute concentration of a homogeneous system is changed, a new phase ca ...
smaller for phasebthan for phasea. This is illustrated in Figure 14.1a. Remembering thatG¼HTDS, we derive that DtrG¼GðbÞGðaÞ¼D ...
This is illustrated in Figure 14.1b, where tany¼DtrH/Teq. It has been implicitly assumed thatDHandDSare independent of temperat ...
phase is not yet present; nevertheless, a phase transition occurs readily, as is explained in Section 14.2.2. Transitionsinside ...
TABLE14.1 Various Kinds of Phase Transitions and the Role of Nucleation Phase change Nucleation? Theoryauseful? Occurs in foods? ...
14.2 NUCLEATION THEORY Nucleation theory is presently in a state of confusion, and quantitative predictions of nucleation rate c ...
thecritical radius for nucleation rcris obtained: rcr¼ 2 g DHVð 1 T=TeqÞ ð 14 : 6 Þ Inserting this into Eq. (14.5) we obtain f ...
equation(10.9), which can be written as RTln sr s? ¼ 2 gV r ð 14 : 8 Þ wheresis solubility andVmolar volume. It gives the equ ...
exponential is much more dependent on temperature than the other factors. This is because a small change inTgives a relatively l ...
ofJhom¼ 1014 m^3 ?s^1 (e.g., corresponding to about 1 in 10mm^3 during 15 min) is often taken. ThenThomwould equal about 408 ...
as most salts, the discrepancies tend to be even greater. In fact, many workers consider the theory to be essentially wrong, and ...
Moreover, the errors vary with the kind of phase transition. Nevertheless, substantial homogeneous nucleation does only occur at ...
using polarized light microscopy, the temperature T and the droplet diameterdare noted. After several repeats, a graph like Figu ...
concentration would be limited, and the larger a droplet is, the larger the probability that it contains at least one catalytic ...
FIGURE14.5 Homogeneous and heterogeneous nucleation. Embryos (radiusr)of phasebformed from phasea(a) in the absence of foreign p ...
«
24
25
26
27
28
29
30
31
32
33
»
Free download pdf
