After working with ‘moo juice’ for a number of years at cafés scattered around the globe, I have come to ask myself one thing; why did that first person milk a cow and drink it?! On a more professional note, I have found that milk is yet another of those pesky variables in coffee making. The final steamed product can vary, not just because it’s skim, hi-lo or full cream, but due to seasonal variations in the milk too.
If you want to read lots of detailed information on the complex topic of milk, take a look at Sapna Kamath Voderbet’s thesis from the University of Queensland in 2007. Today, however, I am going to put it into a ‘café applicable’ context, and cover the two most important questions in the milk world for a café; ‘Why shouldn’t you re-steam milk?’ and ‘What is the best milk for a café to use?’.
Re-steaming milk is a common practice in cafés which don’t mind compromising on quality. Essentially, this can be viewed in two ways. The first relates back to the overall purpose of an espresso coffee machine; the second considers more scientifically the chemical makeup of milk and what really happens when it is steamed.
Espresso as a brewing method is a comparatively recent arrival in the coffee world, having been developed in the last hundred years or so. Essentially, an espresso machine is a small, advanced filter, designed to extract all of the sugar and oil from freshly ground coffee into a cup. The espresso machine allows the barista to make a coffee from scratch, and tailor the coffee exactly the way the customer likes it. An espresso machine does this very efficiently (around one cup of coffee in 45 seconds) for the quality of product it produces. So, in essence, it’s about personalised coffee; the barista grinds the beans especially for you, pulls the shot especially for you and steams the milk especially for you. This is different to the drip filter mentality, where enough milk is steamed for several coffees in advance, and everyone gets an identical product.
The other side of the coin is a little more scientific, but much simpler than you might think! Essentially, the two most important parts of milk are the fats and the proteins. When you steam a jug of milk, the protein is cooked and turns hard, which traps in the air. (Just like when you fry an egg, the white turns from a liquid into a solid.) This happens at 60 degrees Celsius. But if you fried your egg, placed it on a plate and went outside to water the lawn, the egg would cool down, but it wouldn’t turn back into a liquid — it would stay cooked! If you were then to put the egg into a microwave to reheat it, the egg would turn rubbery and taste disgusting, which is exactly what happens to milk if you start to re-steam it!
The other frequently-asked question is, ‘What is the best type of milk to use?’. The answer is very simple; you need to use full cream milk for a top quality cup of coffee. This is due in part to that other important ingredient in milk — the fat, or lipids, as they are known. Lipids add to the texture and mouthfeel of the resulting product, they also add a glossy, creamy appeal to the surface of the coffee.
Skim milk is essential at any café, where a low-fat option is necessary. Unfortunately, it’s not possible to get the same quality of product through skim milk as full cream provides. It doesn’t give you the fine glossy surface and the foam tends to separate a lot more. This is also why it was said for a long time that skim milk is better in coffee, as it is actually easier to texture because of this separation.
And what about hi-lo milk? Honestly, it doesn’t really fit into any category. It sits right in the middle of the fat scale, and offering it as the only option in a café, is really just taking the easy way out! Hi-lo doesn’t have as much fat as full cream milk, meaning it doesn’t give you that absolute quality of product with the creamy glossy surface. That said, it isn’t as low in fat as skim milk, which is the other standard variety.
So, for the best quality coffee, always use cold, fresh full cream milk!