Learn the science behind:
“Making” milk from a cow is ‘easy’, that is, from an engineer’s perspective. As long as a cow is few, and regularly gives birth to a calve, she’ll do all the hard work. She is the ‘factory’. She adds vitamins, minerals, proteins, sugars, and fats to transform water into milk.
Of course, keeping a cow happy and healthy isn’t that straightforward. But, the complexity of making milk is all taken care of by the cow. No need for a chemist or engineer to come in and ‘make’ milk.
Making milk from oats on the other hand is a different story. You can’t ‘milk’ an oat plant. You’ll have to process the oats to transform them into milk. The same is true for most other plant-based milks. So how do we do it?
- Step 1: Grow, harvest & prepare the oats
- Step 2: Extracting nutrients from oats
- Step 3: Adding 'missing' nutrients
- How to use oat milk
Step 1: Grow, harvest & prepare the oats
Oat milk starts out as oats, a cereal grain, grown in a field. After growing and harvesting these oats, they need to be prepared for further processing into milk. Aside from basic cleaning, the most important preparation step is to remove the husk from the grains. This husk is hard and inedible for humans and isn’t used for making milk. After removing the husk you’re left with a firm grain kernel. These are hulled oats.
Steaming to inactivate enzymes
Oats then often receive a hot steam or blanching treatment. During this the oats are exposed to high temperatures. This inactivates any enzymes in the oats. These enzymes could otherwise cause the oats to spoil more quickly. For instance, oats contain quite a lot of fats (lipids). Enzymes in the oats called lipases can break these down, causing the oats to turn rancid over time. By deactivating them the oats can be kept for longer.
The oats are now ready to be processed into oat milk. Optionally, the oats can be rolled into flakier flat particles (rolled oats), or ground into flour. But for a manufacturer, once steamed, the oats are ready to be transformed into milk. If you buy oats in the supermarket, they’ve most likely undergone this treatment already.
Step 2: Extracting nutrients from oats
Making milk out of a grain is an extraction process. You try to ‘extract’ as much valuable nutrients out of the grain, into the liquid, that is, water. Oats are made up of mostly starch (50-60%), a considerable amount of protein (13-20%), fibers, and some fat. Key is to release these from the oat grain itself.
Grind the oats in (warm) water
In order to get as much out of an oat as possible, it needs to be broken down further. It’s why most oat milk manufacturing processes start by mixing the oats with water and grinding them down. Adding water makes it easier to break them down. During grinding you break up the structure and cells within oats. This makes it easier for the nutrients to leave the grain.
Oats thicken in warm water
Generally speaking, the water is kept warm during this process, somewhere around 50-60°C (122-140°F). This ensures that all the components can leave the oats at a reasonable speed. However, in the case of oats, it also causes the oats to thicken the liquid due to the presence of all those starches. In warm water, these starches gelatinize. They absorb water, swell, and burst, causing the mix as a whole to thicken – very much like making a bechamel sauce or water roux. When making oat milk, most manufacturers will want to try to imitate the flow behavior of cow’s milk. So thickening it not a desirable process.
Add enzymes to prevent thickening
It is why one of the most crucial steps of making oat milk is to break down starches into smaller components. Once broken down into smaller bits, the starches no longer have a strong thickening power. There are roughly two ways to do this. You can use acids or enzymes. The effect is similar, but the process is slightly different. Enzymes generally give a little more control over the process, so we’ll discuss those in more detail here.
Remember that you previously inactivated the enzymes naturally present in oats? It may sound counterintuitive to add them back in. However, you’ll be adding in different types of enzymes. Whereas you inactivated those that could spoil oats, you’re now adding enzymes specialized at breaking down starches. These enzymes as a whole are referred to as amylases.
Starch is made up of long chains of glucose molecules. It is a very large type of carbohydrate. Amylases cut these long chains into shorter chains of glucose molecules, or even into individual glucose (thus sugar) molecules. After the enzymatic treatment, you’re left with a mix of carbohydrates of different sizes including plenty of sugars and maltodextrins. How much are present of each depends on the types of enzymes used by the manufacturer as well as the time allowed for them to do their job, the surrounding temperature, and the pH-value of the liquid. You can tweak the sweetness and thickness of oat milk, by controlling this process.
And to extract more proteins
Even though the starch-degrading enzymes are the most crucial ones, manufacturers may also decide to add other types of enzymes. For instance, manufacturers may add enzymes that make it easier to extract the protein from oats.
Stopping the enzymes
Enzymes will continue to do their job as long as the conditions are favorable. To ensure they don’t convert too much starch, you will want to inactivate them. Since enzymes are sensitive to heat, this often involves an additional heating step. If doing this at the end of processing, it can also serve to pasteurize or sterilize the oat milk, to extent its shelf life. In other cases an additional preservation step might be used.
Centrifuging & filtering to remove particles
At this point, a major portion of the oat’s nutrients has been extracted and the oats themselves have been transformed into mush. However, there will still be a lot of particles present. Most of these are made up of insoluble fibers, which as the name says, won’t dissolve in water. These can make the milk gritty. It is why they are often removed at the end of the process, often using a centrifuge or a filter.
Step 3: Adding ‘missing’ nutrients
Most non-dairy milks aim to replicate dairy milk to some extent. However, the composition of oats is very different to that of cow’s milk. It is why manufacturers may decide to add other ingredients to the oat milk to improve the nutritional value of the product.
One of the most commonly added ingredients is additional oil. Even though oats contain quite a lot of fats compared to other cereals, they contain very little fat compared to cow’s milk. It is why manufacturers may add other vegetable oils to oat milk. You will find these labeled on your oat milk packaging.
To ensure the fat doesn’t split from the rest of the liquid, the fat is homogenized and dispersed in tiny fat bubbles throughout the milk. Adding fat can also make the milk a little more creamy.
Adding micronutrients – vitamins and minerals
To replicate cow’s milk, additional vitamins and minerals may be added as well. Since dairy milk is a common source of calcium, you’ll often find added calcium in oat milk. B and D vitamins may be added for the same reason.
Another mineral you may find in oat milk is added salt, sodium chloride (NaCl). In most cases it’s mostly there to add some flavor.
Improving stability with phosphates
There’s a good chance you’ll find some sort of (di/tri)calcium phosphate for instance. The calcium is added for nutritional purposes, as it is in soy milk. The phosphates supply phosphorus, but also help stabilize the milk. Phosphates are known for their emulsification properties and pH (acidity) control.
How to use oat milk
Keep in mind that even though oat milk is designed to look and behave like cow’s milk, it is not the same. In many applications, this might not be a problem (e.g. as a replacer for cow’s milk in pancakes). However, if you’d try to make cheese, yogurt, a (coffee) foam or sweetened condensed milk with oat milk, you’ll find that it behaves differently. It lacks the proteins required to make these products and you’ll have to adjust your process.
Why should you shake oat milk?
Packs of oat milk will almost always tell you to shake the milk before pouring it out. This is because oat milk still contains oat particles such as some pieces of fibers, even if it’s been centrifuged already. Even though they’re small, they’re still there and they will sink to the bottom of the milk due to sedimentation. By shaking the milk before pouring, you redistribute the particles throughout the milk.
Regardless of your situation, you can always just drink oat milk, while being charmed by how we humans have managed to find a way to ‘milk’ an oat plant.
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