WHY can hot milk be whipped into a foam? ⠀ The proteins hav…

WHY can hot milk be whipped into a foam?
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The proteins have curdled in it.
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The albumin and globulin proteins in milk coagulate at 60 °C and their molecules stick together. If you saturate hot milk with air bubbles, films of coagulated protein form around these bubbles. That’s is the milk foam.
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Still commonly cold milk is also poured into the cappuccinator so that the device can control the heating process.