A rose by any other name smells as sweet. Unless it’s an almond. Or an apple. All these woody flowering plants are in the rose family or family Rosaceae. They are all “roses”… Almonds and apples are also in the same subfamily, Amygdaloideae, which is shared by pears and cherries.
What does this have to do with Oats? Well, it’s context for you to understand how different oats are from other cereal grains like barley, wheat, and rice. All these grains are in the same family of flowering grasses, Poaceae. Oats, barley, and wheat are also in the same subfamily Pooideae.
Most people think that grains like oats, wheat, and barley are pretty much the same, but they are not. Oats are about as closely related to wheat and barley as apples are to cherries and almonds. Read on to learn more about what makes oats so different.
The fruit of the flowering grass Avena Sativa of the Tribe Aneneae is the part of the oat plant that is commonly eaten by humans. The grain is known as the groat. The nutritional quality and storage stability of cereal grains has allowed them to be a valuable part of human nutrition, indeed forming the basis of the diets of almost all modern civilizations.
Among the cereal grains, oats stand out in many ways as the most nutritious of all. They have the highest average protein content of all the grains. For human nutrition, proteins have the highest overall quality. Oats also have the highest percentage of oils which helps them to have the highest energy or caloric value. They have high levels of beneficial soluble fiber including beta-glucans and are allowed to carry several qualified health claims in the U.S. These fantastic nutritional characteristics are even more accessible because oats are normally processed and eaten in their whole kernel form. Some varieties of naked oats can be as high as 20% protein. Oats are hypoallergenic and also are distantly enough related to wheat that their prolamin proteins do not, in general, cause people with Celiac Sprue to have a negative reaction. This earns them the moniker “gluten free” when they are uncontaminated.
As a stable form of food for human nutrition, though, oats have not excelled. Of the cereal grains, oats are arguably the least stable and most difficult to use as a human food ingredient. Though there is some longer history of oats used as human food, that history is not very deep.
Until the 1800s, in most of the developed world, oats were known as suitable only for livestock. The exception to this was parts of Ireland and Scotland. In 1755 the famous English writer Dr. Samuel Johnson defined oats as: “A grain, which in England is generally given to horses, but in Scotland appears to support the people”. To this day oats find a much wider use feeding livestock than they do feeding people. In the United States more than 75% of the oats that are planted never leave the farm and are used for grazing or silage. Even including those acres, oats in the U.S. are not a major crop taking up approximately 1/30 the acres of corn and 1/10 those of wheat.
As a food product, they were not widely available in the U.S. until the 1800s, being sold only in pharmacies as an aid to the infirm and to help with indigestion. However, with better marketing, they began to be popularized as a breakfast cereal and wholesome food. Their popularity since then has continued to grow and now the majority of households in the U.S. are likely to have some sort of food containing oats in their pantry. In the last five years there has been a large growth in a relatively new oat-based product, oat milk, so some U.S. households now also have oats in their refrigerator. Oat milk only represents about 1% of the animal milk business but it has recently overtaken soy milk and is second only to almond milk in the plant-based milk category. Soy, almond (you’ll remember a member of the rose family) and cow’s milk are all allergens.
Oats have also found use in beer over the years. Up until five years ago, oats were known mainly for styles like oatmeal stout, where they provided body, mouthfeel, and general “stoutness”. Many more oats are now used in the ubiquitous Hazy IPA’s than are used for oatmeal stout.
Why haven’t oats found more use in human food until recent times? Well, they are not the easiest grain to work with and they have stability issues. It’s taken time to figure out that oats are great for causing stable haze in beer (mostly a defect for the last 200 years) or making hypoallergenic, good-tasting plant-based milk.
Since this is a brewing blog, let’s look a bit more closely at why oats are a difficult grain for brewers to work with:
Structure and milling:
Oat kernels are much longer and skinnier than barley or wheat. Like barley, oats when harvested have a rigidly attached outer hull. Unlike barley, this hull is substantial and compromises almost 25% of the dry weight of the grain. Oats have oils throughout the endosperm and, in general, are not as friable in a raw state as other grains. All these factors cause difficulties when trying to mill oats through a traditional brewing roller mill. It is difficult to set the mill because the grain is so thin and it tends to deform or flake in the mills. Raw oats are very high in lipase. Milling will expose the oil in the grain to the lipase and quickly result in the grist going rancid from enzymatic rancidity. For this reason, raw oats are not sold in a preground form.
Lots of insoluble protein:
Oats are higher in protein than other common brewing grains. Additionally, their proteins have the lowest solubility by far of any of the cereal grains, being only about 10% soluble. Malting can improve this somewhat, but not substantially. High amounts of insoluble protein lead to low yields in brewers extract, and larger amounts of spent grain causing potential runoff issues.
Lipid and fiber content:
Oats are about 3% oil and 3-5% fiber in the form of beta-glucan. Normally the bulk of these materials are not extracted into finished wort. When extracted into wort both these items can cause problems.
For a raw, whole oat 25-30% of the mass is insoluble husk, 12-15% of the mass is insoluble protein, and 11-13% of the grain is moisture. Subtract some of the oil and fiber from the weight and you have a grain that will have a maximum potential extract of less than 50% in the best case of proper milling.
Processing oats for easier use:
Dehulling and kilning:
The inedible hull of the oat can be removed. Because of its tight adherence to the grain at the germ, removal of the hull results in damage to the grain which exposes the oils in the germ to native lipase and causes the dehulled grain to go quickly rancid, as mentioned above. For this reason, oats are “kilned” or heated to deactivate the lipase enzyme immediately after dehulling in order to form a stable kernel or groat. As with malting grains, this kilning process results in the removal of some of the raw flavors of the grain and the creation of pleasant bakery-type flavors. The normal subtle slightly nutty, toasty, vanilla, and cinnamon-type flavors that most people associate with oats are a result of this kilning process.
If you see or buy whole oat kernels (or groats) in the store you are not buying a raw grain, but rather a grain that has already been cooked for stability.
Milling and flaking:
Stabilized oat groats aren’t much easier to mill than the raw grain. Thus, stabilized oats are normally sold in a variety of pre-milled formats. Steel cut or Scottish oats are oat groats that are milled into large chunks or pieces. The oats pass through slits of a specialized mill where they are sheared off by a steel blade, hence the term steel cut. Because the oat kernel isn’t highly friable these sheared pieces stay mostly intact with little flour. Scottish and steel cuts oats take longer to cook, normally requiring 20-30 minutes in boiling water to hydrate and gelatinize. They tend to produce a fairly viscous chunky paste with chewy pieces. This is great for breakfast, but not necessarily the best for getting enzymatic conversion and movement of extract in and out of the kernel. So, though brewers can use steel cut or Scottish oats, they are not common.
Flakes, quick flakes, baby flakes, and instant oatmeal
Oats are commonly flaked to make them easier to work with. They are normally heated to make them more pliable and so they are commonly flaked soon after or in conjunction with stabilizing them. Whole kernels or pieces, like steel cut oats, are passed between rollers which flatten them. This disrupts the internal structure of the grain, similar to milling, while retaining the mass in a distinct flake. For brewers, this structural disruption acts to open up the structure to faster hydration and enzymatic attack while still retaining large pieces of intact fiber and protein for lautering. The differences in the type of flakes are based on their finished size and thickness. Quick flakes are simply thinner versions of normal oat flakes and have a resultant quicker cooking time if you are making cereal out of them. Baby flakes and instant oatmeal are thinner still and cook faster.
For brewers, flakes that are smaller or thinner have faster hydration times and give up their extract easier. Instant flakes, because they are so small and thin, are sometimes harder to lauter because they have less structure remaining. They can also form starch balls or pastes in grist hydration systems of mashes if there is not enough agitation.
Because of starch damage and the resultant pregelatinization and hydration, flakes should not be used with wet mills.
Oats can be malted to change their characteristics for brewing. Raw oats must be used, as stabilized oats will not germinate. Oats do not generate significant amounts of brewing enzymes though the other benefits of malting, namely increased solubility of protein, beta-glucan reduction, and structural disruption can be somewhat achieved. Kilning of malted oats allows for a lower moisture content than a normal stabilized groat, as they are dried to 5-6% moisture vs. a stabilized groat at 12%. This allows for more extract. However, because most malted oats have the hull attached, malted oats have extract values only slightly better than raw oats, normally about 50%.
Lower moisture malted oats are more friable and mill slightly easier, though the hull and thin kernels still provide challenges for brewers. The flavor of malted oats is unique; a malting kiln is a much different device than an oat stabilization kiln so some of the flavors are similar to a stabilized oat, some are not. Oats are well known for creating rancidity and off-flavors if germination is carried out too long or if the low moisture product is stored for very long.
Naked malted oats
Like barley, there are some uncommon varieties of oats that do not have a tightly adhered outer hull. These varieties tend to be higher in protein but are stable without heating in a loose grain form. They can therefore be germinated without the hull and produce finished malt with higher available extract. These varieties also tend to be slightly plumper and, without a hull, they are also somewhat easier to mill. Extracts above 70% are not uncommon with malted naked oats.
Briess produces several oat products tailored to brewing applications,
Our Brewers Oat Flakes are produced to be large thin flakes from whole groats that will easily give up their extract and have larger intact protein and fiber bodies so as not to affect runoff as drastically. They are also stabilized using a torrification process, as opposed to steam, and result in a finished product with slightly lower moisture and therefore higher extract than a conventional food flake.
Our Blonde RoastOat® Malt is malted and then roasted to give unique nutty and biscuity notes. As a low moisture finished malt, it has high friability for easy milling and also high extract values.
Both these products contain non-coagulable soluble oat proteins that can lead to haze in finished beer.