hob wrote:
> "Bob Simon" > wrote in message
> ...
> > I buy the gallon size of milk, split it into two plastic half-gallon
> > containers when I get home, and freeze one. After thawing for a
> > couple of hours, there is still a block of frozen milk in the center.
> > If I use the liquid milk at this time, will it be the same
> > concentration as after the whole carton thaws and is shaken?
> >
>
> I can't speak from direct experience of personally freezing milk
> However, from chemistry, theory says there should be a slight , but not
> significant, difference in fat-containing milk, which depoends on the rate
> of freezing-
>
> 1) There are two immisicible liquids in all but skim milks: fat-based and
> water-based solutions.
> The water has dissolved sugars, etc. The fat has dissolved vitamins,
> etc.
>
> 2) Homogenized milk is a suspension of fat solids in water solution; the fat
> is not dissolved in the milk.
> Homogenizing "breaks" the cold fat into small enough particles that they
> don't float in the water solution Think cold butter blasted into such tiny
> particles that they remain as solids suspended in the water.
>
> (since there is no apparent need to homogenize skim milk, is skim milk
> homogenized?)

Yes, skim milk is homogenized... skim milk is not fat free, it contains
about 1% fat. All that you contributed is correct. Modern
homogenizing methods are very through so milk does not readily separate
when freezing or thawing, certainly not when using modern frost free
freezers and thawing, at least partially, while under refrigeration...
anyone still using old fashioned refrigerators should divide milk into
smaller containers before freezing, but should do the same with all
foods. If homogenized milk were prone to separation it would certainly
do so while under refrigeration and certainly when left at room
temperature, it does not, not to any meaningful degree. Those who claim
their frozen milk separates are doing something incorrectly, or simply
lying... old milk that is just beginning to sour will separate much
more readily... did I mention LYING. Btw, human breast milk is frozen
all the time (a very common practice), and is not homogenized,
leastways not after leaving the breast. hehe


> 3) Dissolving compounds in a liquid lowers its freezing point, but as I
> remember, adding non-dissolved solids in suspension does not.
> The dissolved compounds in the solution do not separate out. They freeze
> evenly.
> (Think salt added to ice-water to make ice cream to lower the freezing
> point, and think frozen confections which freeze with the dissolved sugars
> evenly distributed. )
> I believe suspended solid particles can be separated out only if the
> freezing is done slow enough. Think ore refining to remove impurities, and
> slow freezing with ice extraction used to concentrate solids in suspension.
>
> 4) Liquids frozen in a container do not freeze all at once (supernatant
> excluded).
> There are two conditions of freezing: rapid freezing, where the water
> crystals in contact with the much-colder sides form first and cool so
> rapidly they cannot migrate to the top of the solution, and they grow small
> crystals from the sides, expanding into the rest of the solution, trapping
> most of the suspended particles in the crystal matrix; and slow freezing,
> where the water cools and expands and floats to form large-ice-crystal ice
> on top, ice unable to trap the suspended solids until the convection slows.
>
> Theoretically -
> The water and water-soluble solids should freeze at one temp, lower than
> that of water.
>
> If you freeze the milk and suspended fats fast enough, it shouldn't
> separate.
>
> If you freeze it slow enough , the concentration of suspended particles
> will vary, by location, in the container.
>
> theoretically.....
>
> ---------
>
> Note - due to the expansion of water as it becomes a solid, and that it
> takes time-in-liquid to create large ice crystals, cells containing water
> and molecules which attach to the ice crytal lattice are not damaged by very
> rapid freezing, but they will be damaged by slow freezing due to the large
> crystal formation. That suggests that taste may be affected by slow
> freezing.
>
> > --
> > Bob Simon
> > remove both "x"s from domain for private replies