On food and cooking the science and lore of the kitchen ( PDFDrive ) 43

many of its fat globules rise and form a fatrich layer at the top of the container. This
phenomenon is calledcreaming, and for
millennia it was the natural first step toward
obtaining fat-enriched cream and butter from
milk. In the 19th century, centrifuges were
developed to concentrate the fat globules
more rapidly and thoroughly, and
homogenization was invented to prevent
whole milk from separating in this way (p.
23). The globules rise because their fat is
lighter than water, but they rise much faster
than their buoyancy alone can account for. It
turnsoutthatanumberofminormilkproteins
attach themselves loosely to the fat globules
and knit together clusters of about a million
globules that have a stronger lift than single
globulesdo.Heatdenaturestheseproteinsand
preventstheglobuleclustering,sothatthefat
globules in unhomogenized but pasteurized
milk rise more slowly into a shallower, less
distinctlayer.Becauseoftheirsmallglobules


andlowclusteringactivity,themilksofgoats,
sheep, and water buffalo are very slow to
separate.
Milk Fat Globules Tolerate Heat…
Interactions between fat globules and milk
proteins are also responsible for the
remarkable tolerance of milk and cream to
heat. Milk and cream can be boiled and

reduced for hours, until they’re nearly dry,
without breaching the globule membranes
enough to release their fat. The globule
membranes are robust to begin with, and it
turns out that heating unfolds many of the
milk proteins and makes them more prone to
sticktotheglobulesurfaceandtoeachother
— so the globule armor actually gets
progressively thicker as heating proceeds.
Without this stability to heat, it would be
impossible to make many cream-enriched
saucesandreduced-milksaucesandsweets.
…But Are Sensitive to Cold Freezing is a