Physical Chemistry of Foods
(and an equilibrium water distribution has been reached, which may take several days), we also know that the water content of th ...
can have a much greater mobility than sucrose near the glass transition point.) The diagram also gives the glass transition curv ...
Tg^0 (generally read as ‘‘tee gee prime’’) may be called thespecial glass transitiontemperature; it characterizes the glass tran ...
in unfrozen systems. The values ofTg^0 andc^0 sare, however, more dependent on temperature history. Table 16.1 gives two example ...
order transition. Altogether, some basic problems have not yet been resolved, and it may well be that there is not just a single ...
water content. This can be done accurately for simple mixtures, since the water content can be unequivocally determined. For mix ...
Another option is freeze-drying. Starting with a concentrated solution, freezing will soon lead to a mixture of ice crystals and ...
examples concerning ion association are in Figure 16.9. Most association constants increase upon cooling, but to a different ext ...
Globular proteins can denature at low temperature, for the most part because of decreased hydrophobic interaction; see Figure 7. ...
turn on the type and concentration of biopolymers present. For beef and bread, the curves become horizontal above 308 C, which ...
that very deep freezing is needed to decrease the water activity greatly. According to Eq. (8.3), the osmotic pressure is given ...
entrapped in the glass formed at further freeze-concentration. The consequence of specific substances crystallizing is that the ...
Toensure stability, it is often desirable to keep the frozen product at a temperature belowTg^0. Approximate values are Fruits a ...
decrease plasmolysis, but generally damage the plasmalemma and possibly intracellular organelles. The latter may upon thawing ca ...
Moreover, it should be readily soluble. Glycerol is thus quite effective (M¼92 Da, eutectic temperature 468 C), but it is not ...
Mechanical damage depends on the extent ofvolume expansioncaused by ice formation. To reduce mechanical damage, it is often desi ...
Question Consider a solution of 8.5 g NaCl and 1.7 g glucose per liter. What would be (a) the freezing point of the solution and ...
16.4 RECAPITULATION The Glassy State. A glass is an amorphous solid that shows a glass transition upon heating. A crystalline ma ...
Many foods show the special glass transition upon freezing. For most of these,Tg^0 ranges between10 and 408 C, whereasc^0 Wis ...
BIBLIOGRAPHY Much of what is discussed in this chapter is also treated, with an emphasis on practical usefulness, by O. R. Fenne ...
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