Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 188

Молекулярная гастрономия для креативных шеф-поваров (англ. язык)

also functions to kill any bacteria that may be present in the milk). Homogenisation involves squeezing

the milk through very small holes to reduce the size of the fat droplets. The smaller droplets are less

likely to find each other and combine, so the milk is less likely to separate. The amount of

phospholipids present is no longer sufficient to surround all the new smaller droplets, so some of the

casein particles are attracted to the exposed fat droplets and surround them, further reducing the

clumping of fat droplets by giving them a positive charge.

Milk before homogenisation – the darker outlined circles represent the fat droplets, the lighter outlined

circles represent the casein micelles

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Milk after homogenisation – the darker outlined circles represent the fat droplets, the lighter outlined

circles represent the casein micelles

The effect of heating milk

Milk is extremely stable to heating. It can be heated at boiling temperatures for fairly long periods of

time without ruining. Prolonged boiling is therefore favored because it allows the sugar lactose and the

milk proteins to react with each other via the Maillard reactions, to improve the taste and color of milk.

The casein proteins are very unique in that they are proteins that are not denatured with heat. One of

the whey proteins, however, called lactoglobulin, readily unfolds as milk is heated. As it unfolds, it

exposes some of its sulphur...

whey proteins, however, called lactoglobulin, readily unfolds as milk is heated. As it unfolds, it

exposes some of its sulphur atoms previously involved in disulphide bridges, and these react with

hydrogen ions to form hydrogen sulphide, which is responsible for the characteristic smell that is

produced on heating milk. These denatured proteins will tend to stick to the charged casein bundles,

which keep the individual denatured proteins sufficiently far apart that they will not coagulate.

Frothing hot milk: It is this denatured protein that is surrounds air bubbles when hot milk is whisked,

and produces stable foam.

Skin formation: Since water evaporation will be occurring very rapidly on the surface of the milk, the

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