Dairy Chemistry And Biochemistry

MILK LIPIDS 115

2 4 6

Globule diameter (um)

Figure 3.24 Effect of homogenization on the size (volume distribution) of fat globules in milk
(modified from Mulder and Walstra, 1974).

2. As discussed in section 3.10.1, homogenized milk is very susceptible to
   hydrolytic rancidity because the artificial membrane does not isolate the
   fat from the lipase; consequently, homogenized milk must be pasteurized
   prior to or immediately after homogenization. Homogenized milk is also
   more susceptible to sunlight oxidized flavour, which is due to the
   production of methional from methionine, but is less susceptible to
   metal-catalysed lipid oxidation; the latter is presumably because the
   phospholipids, which are very susceptible to oxidation (highly un-
   saturated) and are located largely in the natural membrane (which
   contains pro-oxidants, e.g. xanthine oxidase and metals) are more uni-
   formly distributed after homogenization and, therefore, are less likely to
   propagate lipid oxidation.


3. Homogenized milk is whiter due to finer dispersion of the fat (and thus
   greater light scattering) and its flavour is more bland.