Green-Mountain freeman. [volume] (Montpelier, Vt.) 1844-1884, 1879-10-29

EDITORS COUNTRY GENTLEMAN: In
discussing the different methods OF setting
milk lately, have been frequently asked
why cream would rise so quickly in the
deep setting system. have replied that
it is because of the greater difference
between the specific gravity of the butter
glubulcs and the milk at II low temperature
han at Il higher one. | based my reason
on the well-known facts of cream rising,
and on the scientific fact that liquids eX-
paud and contract much more under inu-
ences of heat and cold than solids. Re,
Gently have been reading Prof Arnold :
work on American dairying, and when
came to The chapter on raising cream
found he stated directly the opposite to be
the fact. lie says: The differ ence in
specific gravity between milk and cream
is varied by temperature. 1t is greatest
when hot and least when cold, and this
fact materially affects the rising of cream
He also states in the same paragraph that
fats expand and contract more with heat
and cold than water. As these state
mcnts were directly opposite 10 what
investigate the matter closely.
| find in The first place that cream is
treated by all writers on dairy subjects
that | have been able TO consult, rs ii
liquid, and us being subject to The laws
governing liquids. The butter globues
are almost invariably spoken of as gIo-
bulrs Of cream. This brings up the
question what cream is. Cream is not :,
distinct substance of itself, but mixture
Of the solid glohules of butter, with more
or less milk. Cream does not rise. Only
the butter globulcs do that. When lh, y
arrive at the top they remain mixed and
entangled more or less with the milk, and
then constitute what we call cream. The
butter globules are composed of solid
butter, and may or may not be surrounded
by pellicle. They are certainly subject
to the laws governing solids and not those
of liquids. Let us sec what those laws
are so fur as relates TO The phenomena oI
cream rising.
AT the very start we find the law is that
liquids expand and contract more with
heat and cold than solids. Therefore it is
evident ut once that Prof Arnold state.
ment IS wrong, although it would b. right
if the butter globules were liquids. 1t
also at once disproves his assertion tina,
the difference in the specific gravity OF
cream and milk is greatest when hot and
least when cold; for as cream, in the
process of rising, is only the butter glob.
ules suspended in the milk, it is impossi-
BILE for them to cool any more rapidly
than the medium in which they are sus-
pended, and as the milk contracts more
than the solid globuIcs the difference in
the specific gravity Of the milk and the
cream, at Il low temperature, must be
greater than at high emperature-tha,
is, ut any temperature below the melting
point, for of course when melted the but,
ter would be subject 10 the laws of liquids
and will act very differently than when in
solid globules. Prof. Arnold proves this
on page 200 of his book, when in speak ing
of making whey butter, he says that at il
temperature of 170' the cream all comes
to the top in very short time. As butter
melts at 1909. the cream at 100 is simply
melted butter, and will certainly rise very
quickly to tho surface. find also that
many other writer's, in discussing the
action of specific heat on cream raising
fall into the same error in regarding cream
in process of rising ms II liquid instead of a
solid.
They speak of the specific heat of crean
as 07S, when in fact it has no regular
specific heat, never being q constant body.
The decimal 0 rs, as they use it, really
represents the specific heat of the water
in the cream, reduced to that figure by the
admixturc Of the solid fat and the casein,