Learn the science behind:
“Making” milk from a cow is ‘easy’, that is, from a chemist’s perspective. All you have to do is feed and grow a cow, let her give birth and the cow will make milk all by herself. Your cow is your production process or your factory. She adds the vitamins, the minerals, complex proteins, sugars, and fat to transform water into milk.
Of course, feeding and keeping a cow isn’t that straightforward. Not sure I would manage to raise a happy cow! But, the complexity of making that milk is all done by the biological processes within that cow. No chemist needs to mix things up. All we need to do is milk the cow, and we’ve got an amazing blend of ingredients.
It’s less straightforward though for oat milk, one of the many plant milks that have appeared on the market in the past several years. Oats can’t be ‘milked’. They don’t ‘make’ milk. They’re oats. Instead, we humans have to process the oats to transform it into a ‘milk’. (Or, a liquid for us to drink, it varies by region whether you can call the liquid from oats milk or not. But for simplicity sake, we’ll be calling it oat milk for the rest of this article.)
So how do we humans transfer oats into milk?
Oats are a grain, just like wheat and rice. They grow on a plant and need to be removed from the stalks and leaves surrounding the valued grains. The oats themselves are made up of mostly starch (50-60%), a considerable amount of protein (13-20%), fibers, and some fat. When you’re making oat milk, you’re essentially trying to extract all of these components into your liquid!
Oats also contain a component called β-glucans. If you start reading up on oats they are bound to show up since these have been shown to have several health benefits. However, they also impact the behaviour of oats once you’re using them in baked goods, porridge and other applications. In the case of bread, β-glucans can cause the viscosity of a dough made with oats to increase and become sticky.
Oats grow on a plant, so we humans don’t ‘make’ oats, but we certainly process them after harvest. As opposed to wheat flour or rice, where white flour and white rice are most common, almost all oats are eaten as a whole grain version. Almost the entire edible kernel, endosperm + bran + germ is eaten by us.
The only part that manufacturers remove from the oat grains after harvest is the, for humans inedible, husk. Nowadays, manufacturers, farmers, and researchers are working together to develop oats that don’t even contain this hull, skipping another processing step.
After removing the husk you’re left with a firm grain kernel that does have some resemblance to a rice or wheat kernel. These are hulled oats and depending on where you live you might be able to buy them although they are mostly used for animal feed.
Steaming oats to stop enzymes
A lot of oats though are rolled to create the characteristic flat oat flake.
But, before being rolled oats need to undergo a heat treatment. Whereas most wheat flour and rice is sold rice, rolled oats are almost always not raw anymore. This steam treatment is important for extending the shelf life of oats.
Oats contain a lot of very active enzymes. These enzymes such as lipases and peroxidases can cause oats to turn rancid quite quickly. Giving them that heat treatment stops all these enzymes and prevents premature spoilage.
Converting oats into oat milk
So now we’ve got some ready to eat oats, but no milk yet. As a matter of fact, all you need to do to make oat milk is ‘cook’ the oats in milk to break down the oats and release all its ingredients in water!
Making milk from oats can (but doesn’t have to) start after the oats have been transformed into hulled or rolled oats. First, the oats are milled down even further, into a flour. This flour is then soaked in hot water (approx. 60°C/140°F), to extract all components from the oats into the milk. Just about all water in oat milk is added during manufacturing, since oats themselves are dry.
A major challenge for manufacturers though is that during this heat treatment the starches in the oats start to gelatinize. Gelatinized starch thickens liquids, just like potato or wheat starch do. In order to get a more liquid homogeneous consistency, manufacturers solve this problem by breaking down the starches!
Starches are very long carbohydrates. By breaking these up in smaller pieces, their power to thicken the liquid disappears. What you’re left with are smaller molecules such as maltose, a sugar that you’ll also find in malt, as well as some slightly larger carbohydrates. There are roughly two ways to do this. You can use an acid, or, an enzyme!
So even though we’ve first deactivated the naturally present enzymes in oats to improve shelf-life, we’re now adding new ones. These are enzymes called amylases (both alpha & beta types can be used). Amylases are specialized in breaking down molecules such as starches. Once the enzymes have broken up enough starches, you simply re-heat the milk to deactivate the enzymes again!
Want to be updated on new food science articles? Subscribe to our weekly newsletter
Apart from adding enzymes to break down starches, they can also be added to better extract the proteins from oats!
After this enzymatic treatment, the viscosity of the oat milk has gone down considerably and is pretty much ready to go. At this point, manufacturers may decide to remove the insoluble fibers. This gives an even smoother oat milk but removes some valuable nutrients.
Manufacturers may also decide to add a wide variety of ingredients to the oat milk to improve the nutritional value of the product.
Vitamins and minerals can be added. 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. Some oat milks contain added fats and oils, or even a little added salt for flavor.
Looking for a way to use oat milk aside from just drinking it? Consider making some pancakes with them!
Amanda Benenati, Phosphate Functionality in Dairy Applications, April, 2016 issue of Prepared Foods as Developing for Dairy, link
N Bernat, M Chafer, C Gonzalez-Martınez, J Rodrıguez-Garcıa and A Chiralt, Optimisation of oat milk formulation to obtain fermented derivatives by using probiotic Lactobacillus reuteri microorganisms, Food Science and Technology International 21(2) 145–157, 2014, link
Best Food Facts, Plant-Based Milk vs. Cow’s Milk: What’s the Difference?, Feb-28, 2017, link
Aastha Deswal, Navneet Singh Deora, Hari Niwas Mishra, Optimization of Enzymatic Production Process of Oat Milk Using Response Surface Methodology, Food Bioprocess Technology, 2013, link
Aastha Deswal, Navneet Singh Deora, Hari Niwas Mishra, Effect of Concentration and Temperature on the Rheological Properties of Oat Milk, Food Bioprocess Technology, 2014, link
Barbara Ingam, The safety of raw oatmeal, Jan-14, 2019, link
OMRI for the USDA National Organic Program, Technical Evaluation Report: Phosphates, Feb-10, 2016, link
Angeliki Öste Triantafyllou, US6451369B1, Non-dairy, ready-to-use milk substitute, and products made there with, 1998-10-19 (application), link
Angeliki Triantafyllou, WO2014123466A1, Liquid oat base, 2013-02-05 (application), link
Webster, Francis. Oats: Chemistry and Technology. United States, Elsevier Science, 2016., p. 348, link
Functional Foods, Cardiovascular Disease and Diabetes. United Kingdom, Elsevier Science, 2004., p.407, link
Novel Food Ingredients for Weight Control. United Kingdom, Elsevier Science, 2007., chapter 11, link