Love a foamy, velvety latte but don't want to splurge for milk? The team over at ChefSteps has made this awesome video to show you how to get the latte effect with nothing but some instant, plunger, drip or instant coffee; a blender; and a little bit of xanthan gum. But it's not only an awesome life hack for coffee lovers - it also involves some pretty awesome chemistry.
So what's going on here? To understand that, you first need to understand that foam is just any liquid that has gas evenly dispersed throughout it. That sounds easy enough, but in practice it's pretty tough, because a liquid such as milk or water naturally wants to stick together. You're not going to get a liquid to form the bubble film required in foam unless you do something that reduces the molecules' attraction to each other.
So when you make a latte the traditional way - by steaming milk - you're inadvertently doing this by heating up the milk proteins. Food chemistry website Serious Eats explains:
"The proteins chains in milk are polar: one end of the chain is hydrophilic (attracted to water), and the other is hydrophobic (repelled by water). Because milk is mostly made up of water, as soon as those proteins unfold, exposing their ends, the hydrophobic ends immediately try to get as far away from that water as possible. If you were to look at a single tiny bubble in a cup of foamed milk, you'd see that the hydrophobic ends of the milk proteins are all pointed inwards, towards the water-free interior of the bubble, while the hydrophilic ends stay put in the aqueous environment the bubbles are suspended in."
This new structure allows air bubbles to stay evenly suspended throughout the liquid for a long time (long enough to enjoy your hot, foamy latte). But because the plain old water in your plunger or instant coffee doesn't have milk proteins in it, this doesn't happen so easily.
Which is where the xanthan gum comes into things. Xanthan gum is what's known as a hydrocolloid, and it changes the viscosity and stickiness of water. It's commonly used throughout food products to stop things like your salad dressing from separating.
And as you can see in the video above, by adding around 0.1 percent xanthan gum to your coffee mixture (so roughly one gram in a Litre of coffee) you can achieve the same delicious foam effect as you get when steaming milk.
We'll let you watch the video to get the step-by-step instructions because it looks so good. But next time you're feeling bored of your morning black coffee, just remember that chemistry has your back.