What Makes Colloidal Oatmeal Colloidal?

I've been on an extensive, several-part research session that turned up differing answers, more questions and a whole lot of interesting info about microns, particle sizes, and oats for skincare that we're going to be looking at today.

Who could imagine oats could be such a mind-blowing ingredient?

But I'm getting ahead of myself.

Get ready for a bit of a ride as we examine colloidal oats, because there are going to be a few twists and turns along the way!

It All Started...

It was discussion with some colleagues about the correct process for making colloidal oatmeal that started this whole thing. Some were convinced colloidal oatmeal could only be produced via several steps that entail boiling in water, drying, and subsequent filtering. Others were convinced making colloidal oatmeal was 'merely' a matter of grinding/milling oats to a certain particle size.

Guess what.

Everyone was right.

But before we get into the processes of making colloidal oatmeal, we need to take a peek at the difference between colloidal oatmeal and ground oats and oat flour.

Colloidal Oatmeal vs Ground Oats vs Oat Flour

If you grind up a portion of rolled oats (what we did on this post), your result (unsurprisingly) will be ground oats. A coffee grinder and lots of sifting may get you a fine, powdery result, but still won't get the particle size down far enough to call it colloidal oatmeal.

Go ahead and add your ground oats to a powdered face cleanser or face mask, but if you incorporate it into an emulsion (say, a lotion), it may create undesirable lumpy-bits.

In short: ground oats have more limited uses than colloidal oatmeal in a cosmetics-making setting.

Colloidal oatmeal is processed from whole oats and includes the bran, but has a smaller particle size than can be achieved in a home setting (more on that in a minute).

Oat flour is made from oats where the bran has been removed. By removing the bran, it's possible to mill the oats to a much finer particle size. This is great if you want to add a bit of texturizer to your product, but not at all great if you want all the documented skin-loving properties that colloidal oats offer.

In short, without the bran, the oats just ain't grand.

So, What's in Oat Bran?

Colloidal oatmeal and ground oats (from whole oats) includes the bran and therefore contains actives such as:

• lipids (unsaturated triglycerides that help replenish the skins oils) 
• beta glucan (moisturising) 
• avenanthramides (anti-oxidant unique to oats) 

Colloidal oatmeal is anti-inflammatory, helps soothe itchiness and offers barrier repair.
Oats also contain a small percentage of saponins, which are great for cleansing activity.

The bran is – quite simply – where the actives are.

Colloidal Oat Confusion

Now that we know the difference between oat flour, colloidal oatmeal and ground oats, one would think there was nothing more to discuss (or research).

One would think.

But while I was researching colIoidal oatmeal, I kept running into this:
The INCI name for colloidal oatmeal is: Avena Sativa (oat) kernel flour 
The INCI name for oat flour is: Avena Sativa (oat) kernel flour 

Do you see any difference in these INCI names?

I sure don't.

It seems you can't be quite sure of whether or not you are purchasing oat flour or colloidal oatmeal just by looking at the INCI name.

Obviously, more research was in order.

The International Cosmetic Ingredient Dictionary and Handbook defines colloidal oatmeal as finely ground oatmeal; the definition does not specify which species of oat is needed/desired/required.

I checked a few places to see what they had to say about colloidal oats. Here are some highlights:

CosmeticsInfo.com writes: 

Colloidal Oatmeal is finely ground oatmeal. It is often used to relieve minor skin irritation and itching due to poison ivy or insect bites. It can also be used as a soak, compress or wet dressing. When oatmeal is used in cosmetic and personal care products, it may be called Avena Sativa (Oat) Kernel / Meal.

Oat Cosmetics writes:

Colloidal oatmeal is a natural cosmetic ingredient obtained from Avena sativa (oats). The whole oat grain, including the bran layer, is milled and sieved. This results in a light cream coloured, fine powder. 

Aroma Zone describes their colloidal oatmeal as such (Google translated from French):

This powder is called colloidal because the fineness of its particles allows it to form a homogeneous suspension.
Particle size: 44 microns

(note the micron mention - we're going to be looking at that in a tic)

I emailed Maggie Ghanem of Formulator Sample Shop to ask if she could explain a bit about about colloidal oats and she was kind enough to provide me with this:

Colloidal Oatmeal is made of finely milled oats from the Avena sativa plant. It consists of sugars, amino acids, lipids and fibers. Colloidal Oats are grounded, boiled and steamed. Oat grains are milled into fine powder that will produce a cosmetic agent that can be used as an addition to baths, powders, and moisturizing creams. 

All in all, there's some great info here, but the mention of microns and particle sizes raised even more questions.

We need to get a teensy bit nerdy now, but stick with me and I'll try to make it as entertaining as possible. Here's a quick peek at Wikipedias illustration from the previous post again.

Microns, Nanometers, and Colloids

The upper limit size for particles in a colloid is generally defined at 1000 nanometers. That means, each of those little green particles you see up there on the left should be under 1000 nanometers in size.

1000 nanometers is equal to 1 micrometer - commonly called micron.

How tiny is a micron?

Well, 15 microns is the same as 0.015 mm in size (that's 1.5 hundredths of a millimeter).

Now, remember Aroma Zones product description above? It mentions a particle size of 45 microns. That is the same as a particle size of 0.04 mm (read: four hundredths of a millimeter).

Colloidal Oatmeal Particle Sizes

Now let's look at the particle sizes of colloidal oatmeal, which consists of about 20% starch particles and 80% oat-y particles.
The starch particle size is between 10 - 25 microns.
The oat-y particle size is described as 'below 75 microns'.

I know you're seeing this too. 

Something doesn't fit.

The particles in colloidal oatmeal are massive! They have a diameter well above 1000 nanometers. 

Colloidal oatmeal particles are too big to be classified as a colloid.  

If you want to get completely and utterly technical, even colloidal oatmeal isn't colloidal.

This was pretty much my reaction to this information. 

But, instead of panicking and deciding the world was about to end, I decided to keep digging around and asking even more questions.

There was still the matter of production processes for colloidal – which was the correct method?

With the help of a very patient and gracious expert in the production of colloidal oatmeal, I finally found the answer (he has a special mention at the bottom of this post).

Production Processes for Colloidal Oatmeal

The Dry Way: If you have the right equipment (and no, we're not talking about a pricey super duper kitchen machine), it is indeed possible to dry-produce colloidal oats. The main challenge is the natural fat content of oats (about 7%) which tends to gunk up the 75 micron sieve it has to pass through, but as long as at least 80% of the oats can pass through the sieve, it's OK to label the packet 'colloidal oatmeal'. Granted, this method takes some real advanced milling equipment that not many have, but it is indeed do-able.

The Wet Way: Producers who employ 'the wet way' of making colloidal oats will use a process called pre-solubilising the oat starch. This means they soak the oats (and do other magic secret proprietary things) to separate the oaty bits from the starchy bits. This process changes the structure of the starch and allows the producer to achieve an acceptable colloidal oatmeal particle size. 

So, everyone in the discussion was right!

Don't you just love it when that happens?

But wait!

There is still an unanswered question!

The Unanswered Question

Since the INCI name is identical on oat flour and colloidal oatmeal, how can we tell what are buying?

Here's the kicker. 

I don't have the answer.

I can only offer this advice: ask your supplier. Be kind, but be persistent until you get a satisfactory answer. Be patient. It could take a few weeks, because sometimes the distributor (not being the producer) won't be able to answer you until they do a bit of digging and asking on their own first. 

Do Tell

Do you use colloidal oats, ground oats or oat flour in your products?

More About Oats for Skincare, Colloids, and Avenathramide

Google answers: how colloidal oatmeal is made
Colloidal oatmeal; history chemistry and clinical properties
What is a colloidal oatmeal: Cosmetics Business
Anti inflammatory activities of colloidal oatmeal
Colloidal oatmeal formulations as adjunct treatments in atopic dermatitis
Cosmeticsinfo: Avena Sativa Oat Kernel Meal
Cosmetics and Toiletries: Colloidal Oat flour for skin and hair
Avenathramide
U.S. Pharmacopeia: Colloidal Oatmeal
Colloidal Oatmeal: history, chemistry and clinical properties
Safety Assessment of Oat derived ingredients as used in Cosmetics
Scientific American: Creating your own colloid
Particle Size: Wikipedia
Nanoscale
Micrometer Conversion scale

A special thanks to Cark Maunsell at Oat Services for his kind assistance and patience with all of my questions.