Physical Chemistry of Foods

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using polarized light microscopy, the temperature T and the droplet
diameterdare noted. After several repeats, a graph like Figure 14.4 can be
constructed. There is considerable scatter in the crystallization temperature
of droplets of a given size, but the average Tis lower for a smallerd.
Moreover, below a certain value ofd, the lowest temperature observed does
not decrease any further. It is concluded that this must be the homogeneous
nucleation temperature, in the case of trimyristin 21 K below Teq(this
concerns thea-modification: see Section 15.4.2).
It is further concluded that at temperatures aboveThom, nucleation is
induced by small particles called catalytic impurities. Their number


FIGURE14.4 Crystallization temperature T observed in droplets of various
diameterdin an O–W emulsion of trimyristin (tri-tetradecylglycerol). The average
temperature and the lowest temperature are given.Teqis the equilibrium temperature
(clear point) of trimyristin. See text. (After results by L. W. Phipps. Trans. Faraday
Soc. 60 (1966) 1126.)

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