Physical Chemistry of Foods
Gravity, as in the percolation of hot water through ground coffee An external mechanical pressure, as in ultrafiltration Capilla ...
The very low permeability of several gels is the main reason why they hold water tenaciously. For very narrow pores, say 10 nm, ...
5.3.2 Effective Diffusion Coefficients Even for such a simple case as the diffusion of a small-molecule solute, say sugar, in a ...
Numerous theories have been developed for diffusion in compound systems, and they all depend, of course, on the structure of the ...
Electrostriction. Ions diffusing (or being subject to flow, for that matter) through a matrix that carries an electrical charge ...
In most foods of high or intermediate water content,Dis not very much smaller thanD 0 , rarely by more than a factor 10. For exa ...
Common sense suggests, and Eq. (5.26) predicts, that D*¼0if rm 5 rp. This is, however, not the case. Even in a crystalline solid ...
would be negligible for the back fat. However, for the meat the value is somewhat above 0: 5 c 1 , and for the fat about half th ...
Many packaging materials act in much the same way. Another application of Eq. (5.27) has been the development of ‘‘edible films, ...
substances over a membrane against a concentration gradient exist; thereby, passage of these substances through a tissue will be ...
volume fraction. The extent to which a substance can increase viscosity is expressed in the intrinsic viscosity (relative increa ...
temperature gradients. The rate of these processes depends on the diffusion coefficient, which is inversely proportional to visc ...
comply with the concomitant decrease in volume, this means that it will become dehydrated. The diffusional resistance of a thin ...
A. E. Scheidegger. The Physics of Flow through Porous Media. Oxford Univ. Press, London, 1960. Diffusion in gels and similar mat ...
6 Polymers Almost all foods contain macromolecules and almost all of these macromolecules are polymers. Polymers have specific p ...
Nevertheless, a polymer molecule cannot be treated as a simple, compact colloidal particle. Because at all monomer–monomer bonds ...
If several different monomers are involved, the molecules can be far more complicated. Branched polymers occur, and various mode ...
TABLE6.1 Properties of Aqueous Solutions of Some Polymers Stiffness Intrinsic viscosity Name Monomers or building blocks nM(Da) ...
consistency (Section 17.2.2) or to provide stability by arresting or slowing down the diffusion of molecules or the leaking out ...
In this chapter, the properties of ‘‘hydrocolloids,’’ i.e., water-soluble polymers, are primarily discussed, in relation to the ...
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