Since my blog on 'milk', there have been countless times I've thought about writing another short piece on milk and why good baristas will only steam milk to luke warm temperatures. Despite what you all think, there are very good reasons for this.
Don't get me wrong. Personal preference is fair. I get it. However, here are the facts of which you might not be aware.
The reason some people prefer their coffee scolding hot is because they are used to instant, or possibly plunger, coffee that is made using boiling water. For espresso, the addition of milk means the milk must be steamed which means forcing air bubbles into the milk to attach to the protein as it heats. The lactose in the milk becomes sweeter as the temperature rises and a smooth and silky texture is obtained.
When milk exceeds 65 - 70 degrees it rapidly begins to break down and as it approaches boiling point the milk not only loses its texture but begins to sour which in turn, sours the flavour of your coffee. It makes no difference at all that one may take their time to drink the coffee and when it cools enough to drink comfortably the flavour remains in tact. It doesn't. The chemical change in the milk has still occurred and the milk, even though cooled, still has no texture and still a sour flavour.
Soy milk is different again. While the process of steaming is the same, one must be much more vigilant as over heating soy milk can be a disaster. Beyond 60-65 degrees soy milk can curdle when added to coffee. This happens due to the acidity of coffee. Black coffee is more acidic than soy milk and can make your soy milk coagulate which looks and tastes awful. This process is accelerated when soy milk is too hot.
NB Once the protein is heated, in fact 'cooked' it cannot be cooked again and this is why we cannot re steam milk.
PLEASE... To all those who drink their milk based coffee 'extra hot'... try it at 65-70 degrees. The milk will have texture and a sweetness that will surprise if not amaze you and might just give you a coffee drinking experience that you haven't had before.
You won't burn the roof of your mouth either. :)
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