A Beginner's Guide to Steaming Milk

Welcome to today's installment in the Beginner's Guide to Coffee. And today's video is all about steaming milk. Here's how it's gonna go. First of all, we're gonna jump straight into the technique, how to steam milk to get a really fine, moussey texture of foam that you can use to pour latte out if you want to, or just drink and enjoy because it feels so good. Once we've understood the technique, then we'll dive into a few more bits and pieces. We'll cover the science of this stuff. We'll cover alternative milks and different kinds of dairy milk. We'll cover troubleshooting. And make sure that not only do you understand how to steam milk, but what to do if you have a problem and it doesn't go the way you want it to. So let's start right at the beginning with how to steam milk, the technique of it. Now, this is a technique you're gonna use for any machine that has a traditional steam wand. That's generally got a metal tip on the end with one to four holes where steam comes out. Now, not all machines have traditional steam wand tips. So if yours doesn't have that, it might have a weird little plastic wand or some level of automation. Really, the answer is read the instructions and do what the manufacturer tells you to do. But if you've got a traditional steam wand, you should be able to create really beautiful milk texture. So where to start? Well, first of all, you're gonna start with cold milk. So we're gonna be steaming in a stainless steel pitcher. That's useful because you can touch the side and feel exactly how hot the milk is. We'll come to that. The size of the jug determines the amount of milk that you're gonna steam, right? You don't wanna steam in a massive jug just a little bit of milk, and you don't wanna steam a lot of milk in a small jug. So work appropriately. You never really wanna fill a jug above where the spout starts on the side here, right? That's a good max line for most jugs, in my opinion. You'll add some volume to the milk when you steam it, and the motion of the milk in the jug will drive it up the side of the walls. So if you fill above this line, you risk a terrible mess. So that's your kind of max limit, and you can get various sizes of jugs. This would do like an eight-ounce drink or a 250-mil drink quite comfortably if you're doing them one at a time. You could probably squeeze two smaller drinks out of it if you wanted to. Then you're gonna add cold milk. Now, we'll talk more about different kinds of dairy milk and non-dairy milks later on. I'm not gonna use dairy because I don't drink dairy. I'm gonna be using this because I helped develop it, and I really like it, and it steams just like milk. Now for the sort of theory practical bit of what we're trying to do. You're trying to do three things when you steam milk. Firstly, you're trying to make it hot. As long as steam is going into milk, as long as the process is happening, that's happening. So your milk will heat up in a pretty linear way during the sort of steaming section. So that's number one. Trying to heat the milk no hotter than 65 degrees Celsius, I would say. I'll explain later on why. Now, there are two other things we wanna focus on when we're steaming milk, and we're gonna look at those kind of one at a time in the process. So the first thing we're gonna do, and we'll start doing it as soon as we start steaming milk, is essentially blowing bubbles. To make foam, we have to inject air into the milk, and we can do that using the very tip of the steam wand. When that sits on the surface of the milk, then the pressure of the steam coming out of the wand drags in air from around it into the milk, and it essentially blows big bubbles. And the more bubbles that you blow into the milk, the foamier your milk is going to be. Now, you wanna do this part of the process really as quickly as you can. Not so quick that you lose control over it, because you wanna do this with some intentionality, with some purpose, but you wanna get it done pretty quickly. Because the second thing you wanna focus on, and the second, really two thirds of the process, is texture. We're gonna use the steam wand like a hot whisk, and it's gonna take our big bubbles that we blew at the start, and whisk them down smaller, and smaller, and smaller, and smaller, and smaller, until they're so small, they're pretty much invisible. And at that point, you have what's called microfoam. You have a foam that feels just marshmallowy, and soft, and beautiful to drink, and you've made a great drink. Right, that's the goal. So we're gonna heat milk for the duration. At the start, we're gonna add our air, and in the second two thirds, we're gonna texture that foam. We're gonna whisk it down to the smallest bubbles we can make. Now let's look at how you do that in a more practical sense. Now, steam wands on most machines have some movement to them. And generally, you wanna have it pulled away from the machine, sort of pointing out towards you. Have a little movement there or there, but obviously don't do something weird like that. I would say just away from the machine a little bit, and that's good. Now, to line things up, you're gonna use the spout of the jug. Your steam wand's gonna sit inside that spout, right? So you can just slide it all the way in. Now, putting the steam wand into the milk, you only want it to go as deep as the tip on the end of the wand, right? You can see there's always a join where that tip meets the rest of the wand. No deeper than that. There's no point, it doesn't help you out. So just that deep. The last thing to do is to add a little bit of an angle to your jug, right? Like you tilt your jug, for most people, slightly to the right, but you can tilt to the left. It depends on the sort of space around your machine, but you know, not dead on, slightly angled. We're gonna do that to help with the second stage where we're trying to whisk the milk around. Before you start to steam, do make sure you purge your steam wand. In many cases, you'll have a little bit of condensation that you wanna get rid of and get that out. In other cases, you may actually have a little bit of air still in the system, and you don't wanna accidentally blow a big sort of uncontrolled bubble into the milk, right? So just purge the wand, get it ready to go. Then get the jug into place. Now, to explain the process a little bit better before I do it, what I'll do is I'll show you steaming water to explain the position of the steam wand while we steam, because once you're steaming, it's a little bit more difficult to talk about. So you've got your jug in place, right? The angle's right. The steam wand tip is just under the surface, and then you're gonna start to steam. And then just about every machine out there, you kinda wanna go straight to full power, right? You don't wanna go to half power, a little bit. You just go on. And I like machines that just let me go straight all the way to on. Now, as soon as you turn the steam wand on, you wanna begin to lower the jug to bring the tip right to the surface of the milk, right? Not quite above it, but just at the surface. And you'll know it's in the right spot because you'll begin to see and hear and feel air being blown in, right? You'll be able to hear a kind of slurping noise, feel the kind of vibrations of the steam blowing bubbles in the milk. You wanna do this to create as much foam as you need for the drink that you're making. For example, if you're making a cappuccino, I would say you want a good amount of foam. You wanna have the tip on the surface until you've created, say, an additional 50 to 80% in volume, right? That will give you lots of foam. If you're trying to pour fancy latte art, you maybe wanna add 20 to 30% volume only so that you have a thinner foam at the end of it. Either way, you're trying to get this done really early in the process. And as soon as you've added as much air as you need, you're gonna raise the jug back up and stop the foaming process. All you wanna do is see the milk roll and spin and churn. And that's why we had our jug at that angle, to help create that vortex where the steam is just gonna be whisking and swirling all of those bubbles, smashing them down to be smaller and smaller and smaller. If you're comfortable, use your hand on the side of the jug. And when you reach the point of discomfort, you're probably around 50 to 55 degrees Celsius. Going on another three or four seconds will get you close to 60, which I think is a great drinking temperature. And another two, three seconds, maybe if you wanna go to 65, which is where milk tops out. So that's the process. And I'll do it again now live and go through in real time how it would be to foam milk. Jug is in, off to a side. Hit steam. Lower the jug. You can hear that slurping sound. And when I've made enough volume, I'm just gonna raise the jug back up and go into that churning phase. Getting close to about 55 degrees C now. Take my hand off. And stop. First thing you should do is put the jug down. Forget about it for a second. Clean your steam wand purge it out. You actually want the jug to do nothing at all for a little bit and I'll tell you why. Even the most practiced person can end up with a few slightly larger bubbles than they would want. The process of pausing here before you tap allows those bubbles to get weak and then they pop easily. And then you can begin to swirl the milk and foam together again until you see a gloss finish in the jug. At this point, you can pour this into coffee and create a beautiful drink. And you can pour the milk and foam together because there's enough liquid in the foam that it'll pour. If you look in the jug and it has a matte finish, when you tilt, just liquid milk will come out and the foam will almost sit as a raft and sit back from the edge and you won't have a good time. So really, really, really make sure you mix the two together. It should be a gentle mixing motion. Don't be too aggressive. You don't wanna make new bubbles, but you just wanna make sure that you've got the silkiest, most kind of glossy looking milk before you pour it into your drink. So that's the process. That's how to steam milk. And really, all you're changing for different drinks is how long you're doing that kind of stretching phase for, that kind of foaming phase at the start of the process. Everything else, whether it's kind of thick, moussey cappuccino foam or very thin, quite delicate foam that you might want for a flat white, it's the same process otherwise, right? Like it's the same, start cold, add the air, churn it around as much as possible and stop. That's it. Seems pretty simple. But it goes wrong for people in lots of different cases and we should talk about why. And let's briefly talk about the science of milk foams. It does become relevant later on when we get into troubleshooting. So let's talk about foaming agents in things. And we've touched on these before in other videos, but a quick recap. Now it's proteins in the milk that are involved in the foaming process primarily. And the way it works is this. They're a little bit like, a little simplified, but kind of long noodles that are all kind of coiled up and wrapped around each other because parts of it really are repelled by water, right? They are hydrophobic. And they face each other, giving it its shape. Now, when you very slightly denature that protein, and there's a couple of different ways to do it. You can heat the protein up or essentially you can do it through a whisking action, right? If you think about say a meringue, that whisking action is actually denaturing some of the proteins in the egg white and forcing the bits that sort of hate water to come away from each other. And at that point, the bits of the protein that hate water are trying to find anything that isn't water. And what we've done when we foam milk is create a big air bubble that's very appealing to the bits that hate water. And so what happens is that the protein wraps itself around the air bubble on that surface, thus making the bubble strong. It's called a surface active agent or a surfactant. And that's what makes milk foams stable or egg white foams stable. In fact, most foams work in this way. Now, what we're doing when we're steaming milk is actually mixing those two things into denature the proteins, right? We are whisking with the violence of the steam going into the milk as well as heating it up, right? So very quickly, very effectively, we can denature these proteins to the extent that they will wrap themselves around air bubbles. If you're trying to foam cold milk for something, you'll notice it can be done. It just takes an enormous amount more effort and heat is a really nice kind of shortcut, which is why steaming can happen so effectively and still get such good texture at the end of it. So that's why things foam. And anything that has surfactants in it will foam. And that's why a great way to practice steaming milk is not to use milk, but to use a little bit of water with a drop, literally a drop of washing up liquid. Let me show you. This is a super good way to practice with as little waste as possible, but really we're talking like a drop. And this, you would go through the same process. You would steam the same way to get a very similar result. So that's the why things foam part, but let's talk about why things may not foam properly. And for that, we need to discuss fat. Now, if you've made meringues, you will know that you should not get any egg yolk into your meringue mix, because that will cause trouble because the fat there offers kind of competition to the air bubble. It's not water either. And so the parts of the protein that are looking for not water will happily sort of wrap themselves around fat. So fat destabilizes foams in many cases. There are exceptions to this and it does get complicated, but it is basically true in most culinary cases. And certainly it's an issue with milk. If you steam whole milk alongside skim milk, you'll find it's much easier to sort of foam or essentially make more volume in the skim milk. Air that you put in stays in, whereas with full fat milk, you have to work a little bit harder to increase the volume. That's because that fat is kind of competing with the air bubble for the protein's attention. Now, again, in the case of dairy milk, fats are important here because of the way that the fats in dairy milk break down. A bunch of those fats are called triglycerides. You've probably heard that term at some point. It's a glycerol backbone with three fatty acids attached to it. And when that breaks down, you get your free fatty acids and you get free glycerol. Free glycerol in milk is highly competitive with air for the protein's attention. Milk that has been exposed, let's say, to a ton of daylight will foam worse than milk that has been properly stored. So generally milk foams better the further it is from its use by date because it's the sort of breakdown of these fats that reduce its foam ability. And milk that foams badly or milk that has this issue, you'll hear it almost fizz in the pitcher afterwards. If you lift it to your ear, you'll hear a kind of popping sound of all of the bubbles just popping away. And you'll have probably experienced this. And sometimes dairies say, oh, it's, we changed the feed of the cows or some other thing. It's often just poor handling on the supply chain, though in some cases, yes, it is indeed feed that changes the sort of nature of the fats in the cow's milk. So in some cases, if this is happening to you, you do everything right and then just these big bubbles appear in the milk afterwards and it kind of feels like it's breaking down. It's not your fault, it's the milk. And there's some free glycerol in there most likely causing you some problems. The fat has began to break down and there's nothing you can do to make that steam any better. There's nothing you can do in terms of technique or anything else. That milk will probably taste completely fine if you want to use it for something, but it isn't going to be great to foam with ever, no matter what you want to do. One quick thing about fat that's also worth noting is that fat affects flavor release in a drink. A full fat cappuccino will have a different flavor profile to a skim milk cappuccino. In a skim milk cappuccino, you'll have a strong burst of coffee flavor that won't really linger, but with a higher fat content in the drink, you'll have a less intense release of flavor that goes on for a lot longer. And I think that's kind of an interesting aspect of how fat influences flavor. So now we need to talk about temperature because I've given guidance on temperature. I've said 55 is a kind of good starting point to be turning it off from. That temperature, it's very drinkable straight away. It's nice sweetness, but no hotter than 65. And really that's because at 68 degrees Celsius, milk begins to permanently irreversibly change. Think of it like cooking an egg. Once you've cooked the yolk, there's nothing you can do to undo that process. It's a permanent change to the proteins. They've been permanently denatured. Above 68 degrees Celsius, proteins begin to permanently break down, or in some cases, literally just break apart and you'll get the release of some things that add some kind of cooked unpleasant eggy smells to the milk, and that's unavoidable. If your milk spends time above 68 degrees Celsius, you will break it essentially, and it will not taste as nice. And that's why really great cappuccinos are never really that hot. Now, because of the way that heat affects the proteins, if you steamed a batch of milk and you didn't pour it out of the jug, in fact, you just let it cool down and put it in the fridge, chilled it back down again, when you steamed it the second time, the proteins would begin to fall apart earlier because they'd been affected the first time you steamed them, the first time you heated them. So that's why you can't really effectively reuse milk for steaming and have it taste as good or produce as good a texture. You've just damaged the proteins twice, too much, too many times, and they can't give you the texture or the flavor that you want. Now, the perceived sweetness of milk is kind of interesting. That's also temperature related. The sugar in milk, in dairy milk anyway, is typically lactose, and that's designed to be at its sweetest at body temperature, for I hope fairly obvious reasons. But the further you get away from body temperature, be it hot or be it cold, the less intense that sweetness will be perceived. So very, very, very hot sort of cappuccinos or flat whites will taste less sweet than pleasantly hot ones. And if you let it cool a bit more, it will get sweeter and sweeter and sweeter. Now, with alternative milks, the profiles of sugars are a little bit different. Sucrose has a different curve of temperature to lactose. So you might notice some differences there, but with lactose in particular, there is quite a distinct curve of sweetness around temperature. Now, I did say we talk about alternative milks because they are increasingly popular and common in cafes and in homes all around the place. And generally, the sort of rules of why they would foam and the textures they create are pretty similar. Now, as I said, I have a vested interest here. And in creating a product to foam like milk, yeah, you're thinking about how to use something like coconut for like a fat content or how to use oat for sweetness or fava beans for a foaming aspect there to create a kind of plant-based alternative. And doing that well is difficult. Making something that foams like milk is difficult, but there are more options out there in the world today. Like I can't deny that that's the truth. There are things that just don't work as well. If you're testing them out, you'll find that some out there don't foam as well or don't retain or hold the foam as well. You'll find some variances of texture, of mouthfeel, all of those kinds of stuff. Because getting the sort of fats to work in conjunction with the foaming agents is always kind of tricky. But it feels like if you don't wanna drink dairy, there really are more options than ever. And I would say you should be able to treat it exactly like dairy in the foaming process. So the last thing I wanna talk about is actually steam water tips or how to set up a machine to steam well. Because there's a thing that we need to talk about here, which is the idea of almost pressure versus flow when it comes to steam. Many steam boilers are set to a particular pressure. You'll see a gauge that might say 1.2 bars or something like that. That's how much steam pressure you have. And I would say generally, lots of pressure, one plus bars of pressure is good. And if you're struggling to steam milk, lowering the pressure actually doesn't help you out because that pressure is what's gonna be spinning the milk round. Lots of pressure helps create a vortex in the milk, but you might experience a situation where you're trying to steam just a little bit of milk and it feels like there's just too much steam to work with and the process is over before you've begun. In those situations, that's where you wanna switch out the tip of the steam wand for something like a low flow tip. The pressure of the steam coming out remains the same, but less steam is able to escape. That will slow the process down. It'll give you more time to do what you need to do, to add air at the start and to do the texturing, rolling vortex in the second two thirds. It's definitely something that's easy to do with most machines. They're relatively universal in terms of threading on them. And for most machines, there are options available for the size of the holes and the number of holes in the steam tip. So if you're struggling, don't reduce the pressure, reduce the flow, change the steam tip. That's my kind of advice for steaming very small amounts of milk. Now, I don't know about you, but I think I have deserved a little cappuccino, so that's what I'm gonna make. This is about 150 mils. I'm gonna put a short double in here. We're not gonna get into recipes today. That is gonna be a separate episode of the Beginner's Guide to Coffee, where we'll go through all of the kind of key espresso-based drinks and cover off the kind of recipes and recommendations around those kinds of things. But in this case, I'm gonna pull a shot, steam some milk and pour a delicious drink. Mm, just the texture of well-firmed milk is just a wonderful thing to drink. But now I wanna hear from you down in the comments below. Tell me, what are you struggling with with your milk steaming? Did this help? Did this make sense of the process a little bit more? Was this a problem solved for you? Or is there still something that's frustrating you? Let me know down in the comments below. Share your problems. We'll see if we, as a community, can help you out. But for now, I'll say thank you so much for watching, and I hope you have a great day.