I love latte art. You probably love seeing latte art too. I believe that we eat with our eyes before anything is consumed, and that goes for coffee as well. When I see a beautiful design poured into my cup, it makes me appreciate the drink more, and I feel like it tastes better. As my love for coffee grows, and my understanding of what is happening through extraction, and steaming milk deepens, I have been able to develop some opinions about latte art.
I think it’s important to know what is going on with the milk that forms your latte art. This information is very basic, and the chemistry of milk is way more complex than what I will be sharing. A good steam wand from an espresso machine should produce a dry steam that doesn’t release a lot of water. The steam will heat up the milk, making the natural sugars, specifically lactose, dissolve in the milk, making it sweeter. I also believe that when sugars are heated, they caramelize, and the sweetness is more pronounced. Air is also being introduced into the milk with a lot of force, and this is called “stretching.” This produces bubbles, hopefully micro-bubbles, that will make the milk texture velvety, and taste richer. Once a milk texture that is similar to wet paint (yummy!) is achieved, the milk and coffee is emulsified, and when poured, the milk will lay on top, and a beautifully defined pattern will form. I like to say that this is the ideal situation. But what can go wrong?
If the milk is under-stretched, and not enough air is introduced into the milk, the texture will be too thin, and a rich, delicious mouthfeel is absent from the drink. A pattern will not form, or a loose, out of control pattern will be displayed in your cup.
I have some opinions about over-stretched milk that I have not researched, and hopefully someone can verify if I am correct or if my assumptions are inaccurate. I believe that when you add an overabundance of heat, this causes the proteins in milk to denature, and the milk splits. Also adding too much air will create large bubbles instead of small, beautiful, delicious micro-foam. What I have seen and experienced is that a heavy layer of protein rich foam will rest on top in the milk pitcher, while the sugary, fatty (fat is good) milk is left at the bottom. Typically, this will cause your latte art to look “blobby”, absent of those incredibly defined lines. This leads to the important question: does good latte art make a good cup of coffee?
Yes, and No. The basic rule is: if good coffee is not used, then no amount of latte art will save that drink. That being said, if a beautiful coffee is being used, whether a blend or single origin, then I believe latte art can be a signal that the cortado, cappuccino, or latte will be delicious. It signifies that the texture will be rich, and that the emulsification of delicious sugary, fatty milk, and coffee was done well. We will return to this topic in the future.