Food for Thought: What is the Role of Phytase in Soaking Grains?

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As promised, I’ll feed you a little soaking grains research as I can unravel it. I have so many more journal articles to read, but I think I can at least define phytase and explain its definite and potential roles in phytate reduction.

What is phytase?

Phytase is an enzyme. An enzyme is a protein in a living thing that causes action. Scientists call them catalysts; I’d just call them doers. They make life happen. Enzymes are not always in an active state, but can be dormant and need certain conditions to be activated.

Imagine a vehicle sitting in your driveway. Unless you have the key, it’s just a large object blocking your path. Once you have the key, however, it becomes a mode of transportation and quite useful. Phytase is the key to starting the engine within the grain. Making the phytates move out of the way is not possible without the “key” of phytase. (Am I the Charlie Epps of nutrition? Maybe I’ll have a TV show someday.)

How does phytase work?

The action we want phytase to complete, if you remember our discussion of phytates and phytic acid, is to separate the phytates and phytic acid from one another, thus releasing phosphorus and other minerals trapped in that bond. When activated, phytase attaches to the phytate to help release the phosphorus (phytic acid).

Because it’s an enzyme, phytase must be alive in order to have the opportunity to be activated. Heat would damage or destroy the enzyme, so do realize that we’re only talking about raw foods here. Anything that has been cooked, baked, steamed (rolled oats???) will not have active enzymes.

Where is phytase found?

Phytase is in plants, including grains, as well as in the form of microbial phytase in yeast and sourdough leaven.

Various plants have differing amounts of the enzyme phytase. For example, wheat, rye, and barley have considerable amounts of phytase, whereas corn, oats, sorghum, and millet have little or no phytase activity. Baker’s yeast also contains phytase.

There is even some evidence of phytase in the digestive system, so some researchers think phytates are broken down to a certain extent by normal digestion. However, very few studies have been done on human digestion seeking phytase specifically.

Here is a key quote from one of them: “Studies in humans showed that 37–66% of dietary phytate is degraded during digestion in the stomach and small intestine when the diet is rich in plant food phytases.”(3)   Note: remember that only raw plants, grains, etc count. The American diet includes much cooked food, therefore as a whole we are very low in phytases.

How is phytase activated?

There’s the rub. I have more to learn on this subject, but it’s key to understanding our issue of soaking grains. If phytates are going to be broken away from phytic acid, at least in non-intact grains that can no longer germinate (think flour), you’re going to need phytase. How to get it to leave its dormant state and work on the tough bonds is up for discussion to a certain extent, and I will come back to this topic again later.

One fact I know so far: phytase is activated through germination. That’s why we’re sprouting things this week here at KS. I like to focus on where the research findings are clear and well-documented, similar to last week’s challenge to start some sourdough because that is the most effective way to reduce the phytates in bread.

For cracked grains and milled flour, there are various perspectives on possibility, pH, temperature, and method for activating phytase. More to come!

Phytase in freshly ground grain

Enzymes degrade over time, and once the hull of a grain is broken, they’re more open to the processes that will break them down. Once a whole grain is milled into flour, the phytase content immediately begins to decrease. Therefore, to have the best chance of dissolving phytates and releasing minerals, one would want the highest phytase levels possible. Freshly ground flour is the optimal choice.

Some have asked if soaking or souring freshly ground flour defeats the purpose: if it’s sitting around soaking for so long, won’t the nutrients begin to fade anyway? Although I don’t have strong evidence for this, my common sense tells me that when you use freshly ground flour, the high levels of phytase are then activated by the souring (or perhaps, soaking). Once activated, they aren’t going to degrade. They’re already doing their job. That’s my hunch!

The healthiest bread is sourdough – learn how to make a sourdough starter and bake bread, and WIN the best pans I’ve found for homemade bread!

Sources: 1, 2

3 Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis by Ulrich Schlemmer, Wenche Frølich, Rafel M. Prieto, and Felix Grases. Mol. Nutr. Food Res. 2009, 53, S330 –S375

4 Phytase activity and degradation of phytic acid during rye bread making by Merete Møller Nielsen, Marianne Linde Damstrup, Agnete Dal Thomsen, Søren Kjærsg˚ rd Rasmussen, Åse Hansen.

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23 Bites of Conversation So Far

  1. says

    Great information — thank you. I have been adding a spoonful of whole wheat flour to my steel-cut oats when I soak them to get the extra phytase that the oats lack. Now I’m wondering if most of the phytase is already degraded in the ground whole wheat flour…
    Also, it’s really good to know that raw vegetable phytases help us during digestion.
    .-= Ellen´s last blog ..Cooking with Sprouted Wheat: Pumpkin Raisin Muffins =-.

  2. says

    Thanks for doing all that footwork! I’ve been interested for some time in sprouting, sourdough, soaking etc, but I’m one of those people that really likes to know WHY people say something is healthy. Otherwise, it all just sounds like another fad to me. Thanks for breaking it into small bites too.
    .-= Simple in France´s last blog ..Nearing nine months in France . . . =-.

    • Katie says

      Is it bad that I had to Google Alton Brown to see what that meant? I thought he might be some other, bigger blogger. Food Network? Ya think? I get giddy just thinking about stuff like that; it’s bad for my pride. But now you got me thinking… That would be such fun!
      Thanks! Katie

  3. Rachel Wisdom says

    Sorry – I posted this comment in another place when I meant to post here:

    Thank you so much for all of your research Katie! I’ve been trying to learn more about these things for quite a while as my husband has Crohn’s disease and I’d like to figure out what we can do to help him from a dietary standpoint. It’s difficult though because so much of what I read is conflicting and/or just sounds like hype or bunk.

    One specific thing I am wondering. Have you seen anything in your research about taking a phytase supplement? My dh’s digestive enzyme supplement has some, and I am wondering if all the angst surrounding this stuff (to soak or not to soak, does it actually do anything anyway if there’s little to no phytase left in my flour, etc. ) is pointless.

    That’s the long way of saying, what about a phytase supplement?

    I’m adding you to my Google Reader.

    • says

      Check out the Specific Carbohydrate Diet (SCD).
      It heals diseases like Krohn’s, Colitis, and a whole lot of other conditions. is a direct link to a helpful website.
      I’ve got my son on this diet to heal the effects of celiac disease, which has made his gut quite sick.
      It’s worth your investment of time and energy if you really want to heal your loved one.

  4. Judy says

    Hi Katie,
    I have been doing a of research on phytic acid and the enzyme phytase. I have been baking all of our breads for a few years, and always do a long fermentation because when I started, I learned that a long fermentation released nutrients in whole grains, but I didn’t know why. In recipes that I use for long fermentation, I greatly reduce the amount of yeast that I use using more yeast greatly increased the carbon dioxide and alcohols produced by the yeast which will kill the yeast during a long fermentation.

    More recently, I learned about phytase and phytic acid. The whole thing now makes perfect sense to me because I am also into plants and botany. All seeds, including grains (rice included) contains phytic acid to keep seeds dormant so that they don’t start to germinate in unfavorable condition. When growing conditions become warm and moist, the pytase is activated to release nutrients to the embryo of the seed so that it starts to germinate.

    By soaking grains or by using long fermentation processes in bread making, pytase is activated to release nutrients. One distubing thing that I found out is that the phytic acid in grains, if not broken down by pytase, will actually absorb the nutrients in meals that is eaten with. This is one of the reasons that people in countries having a large part of their diets consisting of grain, such as rice in China, there are more dietary deficiencies that cause such diseases as rickets.

  5. Judy says

    I thought I might also mention that people adding whole grain flours to short fermentation recipes could actually be doing themselves harm rather than receiving the benefits of whole grains.

    • Katie says

      Crazy, right, in light of current US Government recommendations for more whole grains?! Thanks for adding your thoughts and research to the post! :) katie

  6. Sandra says

    I am just beginning to learn about all this phytic acid stuff and I find this all very interesting. I see people referring to ‘short fermentation’ and ‘long fermentation’ and I am confused by what they mean. Please explain.

    • Judy says

      Short fermentation is used in recipes that use more yeast such as 2 tsp or more and the first rise is usually 1 to 2 hours or less. For long fermentation, generally much less yeast is used (1/4 to 1/2 tsp) and the first rise can be from 12 to 18 hours. Long fermentation can be done either in the refrigerator or on the counter, and has a similar purpose as soaking grain or flour. During a long fermentation, the phytase has time to activate and break down the phytic acid to release nutrients in the grain. Any bread recipe can be converted to long fermentation by reducing the amount of yeast and also allowing dough to rise for at least 12 hours. This not only releases nutrients but develops more flavor in the bread.

      • Katie Kimball @ Kitchen Stewardship says

        Thanks, Judy! Your explanation was far better than I would have offered! :) Katie

        • Judy says

          Thanks Katie,
          Healthy foods such as proper use of whole grains, non-GMO foods, and meat from natural fed animals has become a passion for me. I truly believe that most of the health issues of our children and even our aged (alzheimer’s, diabetes, athritis, etc.) are all a result of what we are eating. Everyone can benefit from learning more about healthier diets.

  7. Carmen says

    When soaking oats, is it okay to leave out the acid medium? And when adding the whole grain wheat flour, does it have to be freshly ground? I do not own a grinder and am unable to at all, so I was thinking of just buying Bob’s Red Mill spelt flour to soak. Can soaking their oat flour be good too?

    • Katie Kimball @ Kitchen Stewardship says

      There’s actually a lot of changing going on in the world of “soaking grains” – Amanda Rose of Rebuild from Depression says to skip the acid everyt ime ( She does recommend freshly ground, but who knows? Hopefully there’s phytase in store whole wheat, too. Any oats will have phytic acid, even oat flour, so yes, a soak would be a good thing.
      :) Katie

      • Judy says

        I thought I would add to your post. Oats have more phytic acid than many other grains. So they do need a good soak or long fermentation. Whether the phytase is food in store bought flour depends on the grinding process. Heat destroys phytase. The other down side of store bought grain flours is that the nutitive value deteriorates over time. How much depends on storage methods and time before it is used. This is also true of fresh vegetables. They begin losing nutritional value from the time they are harvested, and continue to lose nutrients during shipping and display in stores. Frozen veggies actually have more nutrition than the ones that can be bought in the store as “fresh”.

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