In my post, Phytic Acid in Grains and Legumes, I shared some of my research which led me to conclude that phytic acid does indeed bind with minerals such as calcium, phosphorus, iron and zinc. If you depend on grains and legumes for a high portion of your diet, then those phytates (phytic acid) could lead to mineral deficiences. This may be one of the biggest reasons that traditional societies fermented their grains. Now the question is, how do we effectively reduce phytic acid? But remember, I am sharing nitty-gritty details. If you find this overwhelming, remember you can simply bypass all of this, know that using traditional methods are beneficial and be happy. But if you want to know more information, then keep reading!
Once again, I feel that I still have many (many!) questions on this topic, and there is a whole lot of research to digest and write about, but here is some of the information I’ve gathered so far.
As you will remember, phytase is the enzyme that neutralizes phytic acid (also called phytates). We produce some phytase ourselves, and those of us with robust probiotic digestive health may produce even more of it. Our bodies should be able to neutralize some of the phytic acid we consume.
Some grains contain high amounts of phytase making it much easier to neutralize the phytic acid in them, while others are a lot lower. Sprouting, soaking in warm temperatures in an acid environment and fermenting also activates this important enzyme. The grains that are high in phytase include rye, wheat, barley, and buckwheat. [i] Grains low in phytase include corn, millet, oats and brown rice. [ii] How effective is sprouting, soaking or fermenting grains? Let’s look first at some of the historical methods of processing grains and then delve into some of the scientific studies done on this subject.
Using the source, Fermented Cereals: A Global Perspective, you get a good idea of a few methods that were used traditionally (and are still used in many places).
For all of these nations and people groups, the art of fermentation is a little different. Many of the Asian ferments use a culture from mold growing on raw or cooked grains. Some nations would actually chew some of the raw grain and spit it out into a pot. The enzymes from their salvia would help break down the grain during the fermentation process (though I have to admit that this American isn’t going to try it!).
Other ferments relied on the gathering of wild yeast from the air, which is turn would turn their foods into a tangy, and more easily digested product. Examples of this include our familiar sourdoughs as well as certain Indian ferments. In Mexico a process using wood ash or lime called nixtamalization is used in soaking corn. I notice that most of these grain ferments take days, so length of time is definitely a factor I also notice that many (though not all) use some type of starter enzyme, especially the Asian ferments. Others use malting and fermenting. One African ferment, Mahewu, takes cooked maize, and cools it. Then wheat flour is added as the “source of inoculum”. After being left in a sunny place for 24 hours, it has fermented. For injera, the dough is inculated with leftover liquid from the last injera dough (like sourdough bread)!. Another, kishk, involves taking boiled wheat and soaking it in buttermilk, then drying it. All in all, there seems to be many methods and there seems to be evidence for using sprouting, fermentation, and soaking in a cultured dairy for preparing grains as a traditional practice
Although there is an almost overwhelming glut of studies, most are just studying one grain and even just one method, so there are a lot of gaps still in my mind. However, I wanted to share a few of the studies as I think that they are helpful.
Sprouting Beans, Lentils and Peas
One study researched the effect that germination had on beans, lentils, and peas. First the legume was soaked in water (with added chlorine, which I do not recommend!) and then they sprouted the legumes for 72 hours at 77 degrees fahrenheit. They found that not only did the legumes have increased crude protein as well as an increased content of all amino acids, but also a significant increase in phytase and a significant decrease in phytates. [iii]
Sprouting Grains and Legumes and Fermenting them Together
Grains and legumes were often fermented together traditionally such as for the batters to make dosas and idli. One study tested the effects that germination (sprouting) and fermentation had. Germination of all of the separate grains and legumes (finger millet, green gram, black gram and chickpeas) showed positive effects on iron and zinc bioaccessibility. The fermented batters of rice and black gram showed significant reductions of phytic acid and tannins levels, but when they added chickpea and green gram to make another traditional dish, dholka, there wasn’t as much of a drop in phytic acid levels. They found that germination of grains increased the availability of iron, but not of zinc, while the fermentation batters using rice and black gram had more availability of both zinc and iron, though for the batter of dholka this was not true. [iv]
Another study found that sprouting peas for 4 days increased the bioavailability of zinc and magnesium. [v].
Sprouting a High Phytic Acid Pea
When a high phytic acid pigeon pea was released by the Department of Plant Breeding in India, they tested it for different methods of reducing phytic acid. They found that germination (sprouting) was the best method of reducing phytic acid ( 35% to 39%), while dehulling, soaking and then pressure cooking also had good results. All in all, soaking, soaking and dehulling, and sprouting and cooking pigeon peas all were effective in decreasing phytic acid and increasing the availability of minerals such as calcium, phosphorus and iron. [vi]
Soaking, Dehulling and Sprouting Cowpeas
Another study found that soaking cowpeas for 12 hours, dehulling of soaked seeds and germinating cowpeas contributed significantly to reducing phytic acid and tannin levels. Dehulling as well as germination increased the digestibility to of both the starches and the protein in the cowpea. [vii]
Four pearl millets were germinated over a six day period and tested to see what the effects were on mineral levels and phytic acid levels. They found that germination significantly reduced phytic acid and that different minerals were lowered or raised according to the type of millet germinated. Overall, the conclusion was that there was a good correlation between antinutirtional factors reduced and minerals being more available through germination. [viii]
Sprouting Rye and Barley
I thought this other study using rye and barley very interesting too. Basically, they took rye and barley and soaked it, then sprouted it and studied the effects on phytase and phytic acid. The soaking alone had some effect on phytic levels in the case of rye, but the sprouting increased phytase, and degraded phytic acid dramatically (84% phytic acid degradation for rye and 58% for barley). [ix] This study was done for better nutritional for animal feed by the way. Apparently no one was thinking of us poor humans.
Using Sprouted Flour to Reduce Phytic acid in Non-Sprouted flour
Another study that I found very intriguing (with promise of being helpful to home cooks), was one conducted with sorghum malted flours. Sorghum was sprouted for 1, 2, 3 and 4 days to get varying degrees of malted flour. Then it was added to non sprouted flour (5% and 10% sprouted flour to 90 to 95% non sprouted) and placed in a warm environment (86 degrees Fahrenheit) with “shaking” for 30, 60, 90 and 120 minutes. They found that the longer the sorghum had been sprouted and the longer they incubated it with the non sprouted flour, the more phytic acid and tannins were reduced. When using the four day sprouted sorghum flour and incubating it for 120 minutes, they had reduced phytic acid and tannins by 92% and 98%!!!![x]
This makes me wonder if we could duplicate this practice at home by adding sprouted flour to our soaking dishes to jump start the process of reducing phytic acid. It makes perfect sense as sprouting does release phytase. So if you add sprouted flour to say, a batter for soaked muffins, it makes logical sense that those live and released phytase enzymes would immediately begin to work to reduce the phytic acid content. Exciting!
Soaking, Fermenting and Using Germinated Flour with Maize
Another study aimed to see the effectiveness of different methods one could use at home to process white maize. Soaking, fermentation and using germinated flour were all studied. This study was really interesting because the most effective way to reduce phytic acid surprised me. Natural lactic acid fermentation slurries resulted in 88% retained phytates. In other words, it only reduced phytic acid by 12%. When a starter culture was used, 61% of the phytates were retained, 39% of the phytates removed. When germinated flour was used as a booster, 29% of the phytic acid was removed. But when they used both pounded maize and maize flour and simply soaked it and then removed the excessive water, the pound maize retained 49% of the phytates (51% of the phytates were removed) and the 57% of the phytic acid was removed when soaking the maize flour. [xi]
A few points here, maize is very low in phytase (the enzyme that helps reduce phytic acid). Using a germinated rye or wheat flour would have most likely had a much higher effect because they are high in phytase enzymes already. Also note that the more finely ground flour had even more phytic acid removed than the coarsely ground maize. We could conclude that it is easier to reduce phytic acid in flour in comparison to whole grains.
Raw Brewer’s Yeast Efficiently degrades phytates in corn and soy gruel
Another study that really blew my mind with new possibility was one that found that soaking with raw brewer’s yeast was effective in degrading phytic acid in corn and soy meal! They also mention that microbes such as yeast and aspergillus are known to produce phytase and aspergillus phytase has been used as an additive to animal feed to improve the phospohorus bioaviability by reducing phytates. [xii] Of course the only problem for the home cook is this, I think that all brewer’s yeast sold to the public is generally deactivated.
Soaking and Dehulling Millet and Soybeans
A 2005 study researched the phytates, phytase activity and iron and zinc levels after the soaking of whole seeds, dehulled seeds and flour of both millet and soybeans. They found that with millet dehulling and milling before soaking helped both the phytates and the phytase to be leached into the soaking liquid and result in phytate reduction. Whereas, dehulling soybeans resulted in a “marked” increase in phytate content, but milling the soybeans helped there be more interactions between the phytates and the phytases. The phytic acid rato to both iron and zinc only decreased slightly with soaking. The most phytic acid reduction was found at 8 hours for millet (I wonder if they only soaked for 8 hours? They may have had better results with soaking for a longer period of time or with a phytase addition since millet is low in phytase) and soaking whole soy beans for 24 hours. They found that cooking the soaked flours in the soaking water didn’t further reduce the phytic acid. [xiii]
Lactic Acid Fermentation of Millet
Because fermented millet slurries are an important food for young children in other countries, there was a study testing to see the lactobacillus bacteria found in these fermentations to see if they had phytase activities. The amount of phytase they produced varie,d, but phytase activity was found in all five strains selected. They also found that lactic acid bacteria also produced amylase (the enzyme that helps break down starch) and α-galactosidase. They concluded that this discovery went hand in hand with previous studies showing that phytates were reduced in millet lactic acid fermentations. [xiv]
I wished that not so many of the studies just used part of the wheat berry. I found one using just the bran and another just the germ. But they are still useful. It was found that sourdough fermentation made protein more digestibile, the concentration of total phenols, phytase and antioxidant activies were increased and the concentration of anti nutritional factor raffinose also decreased. [xv] I was also amused to see that one article looking for phytic acid content in the diet of the modern man in Finland (under the impression that phytic acid is positive) noted that traditional sourdough rye bread was not a good source of phytic acid! It’s generally understood that sourdough bread is very effective in reducing phytates, perhaps one of the best methods.
When oats were sprouted, the phytic acid was reduced from .35% to .11% (or in other words, about 2/3’s of the phytic acid was reduced). [xvi]
QUINOA PHYTATE REDUCTION
I thought that this chart published in the Living with Phytic Acid article, very interesting and helpful. You see that soaking and then cooking quinoa reduces phytic acid by a significant amount, while soaking with whey increases the phytic acid degredation even further. Finally, sprouting and then lacto-fermenting (fermenting with lactic acid) almost completely reduced phytic acid.
|Cooked for 25 minutes at 212 degrees F||15-20 percent|
|Soaked for 12-14 hours at 68 degrees F, then cooked||60-77 percent|
|Fermented with whey 16-18 hours at 86 degrees F, then cooked||82-88 percent|
|Soaked 12-14 hours, germinated 30 hours, lacto-fermented 16-18 hours, then cooked at 212 degrees F for 25 minutes||97-98 percent|
In the same article, Ramiel also mentions a study that I was unable to get my hands on that showed that roasting wheat, barley, or green gram (a legume) reduced phytic acid by about 40%. However, roasting will also deactiviate phytase so when soaking after the roasting period, you should add some type of additional culture that contains phytase (such as sprouted rye flour) to further decrease phytic acid.
Ground Flour and Rolled Oats
On that same note, since a high heat will deactivate phytase, you want to use flour that was ground at a low temperature otherwise it will no longer contain phytase. Oats are also almost always treated with heat, so they will also not have active phytase. Phytase may also decrease over time after grinding, so home ground flour is superior.
I find that there are adequate amounts of studies demonstrating that soaking, germinating (sprouting), lactic acid fermentation and other methods do have a significant effect on phytic acid reduction. It was a little distressing to me at first that we are often simply “reducing” phytic acid instead of completely eliminating it, but 50% less phytic acid is certainly still a much better percentage than 100%. How effective each method is seems to depend on a lot of variables, but most often combining methods, such as sprouting, and then fermenting a grain or legume has the most effect. This isn’t to discourage us from just using one of the methods if that’s all we have time for, but just to say that doing more than one is even better.
How do We Recreate This?
While those in previous generations had grandmothers and mothers to teach them how to ferment their local grains with local methods, we are having to recreate and relearn this process. Here’s a few things to get you started.
First, use freshly ground flour is at all possible.
Moisture is the first thing you need(that’s why it’s often called “soaking grains”).
Warmth The soaking/fermenting period will be much more productive in a warm place. Placing the soaking grains or batter in the warmest place of the house is a good idea, especially in the winter. You can also place in the oven with the pilot light on. You will see that many of the studies above used quite high temperatures. If we wanted to get closer to that, we could try a few things. Placing our bowl of fermenting or sprouting grains or legumes in a dehydrator on a very low setting is one option. Placing it in a warm laundry room is another. Making a little pilot light box is another idea. It also seems that the more cold it is, the longer you will want to ferment your grains or legumes.
Acidic Environment: It’s also important that the soaking water or liquid is acidic. This helps neutralize the anti-nutrients. You should add about one tablespoon of something acidic to the soaking water per cup of water.
Enzymes: I personally feel that using something that is rich in enzymes for your acidic addition, such as whey, raw apple cider vinegar, a fermented beverage such as “Grainsfields”, buttermilk or yogurt, is the best choice as I think that those rich in enzyme additions will help jump start the process of breaking down the grains more quickly. When I read about the traditional fermented grain dishes, I realized that most of them had some type of starter or wild yeast enzymatic action going on. Sourdoughs are naturally acidic and full of wild yeast and enzymes and very effective in breaking down anti- nutrients.
High Phytase Grain added to Low Phytase Grain: Adding a high phytase flour, such as buckwheat, rye or wheat to a low phytase flour or grain such as oats, rice, millet, and corn, can help break down the phytic acid. Think of cornbread with corn and wheat flour. That’s a pretty classic combination and if you soak the corn and wheat flour together you will be able to more effectively reduce the phytic acid in the corn. You should also do this if you roast grains (the roasting adds flavor as well as reducing phytic acid), since the phyase will be deactivated through the roasting process.
Using Sprouted Flour: Even more effective would be adding sprouted flour as the phytase is already active and ready to do business! From the few studies that I read who used this method, it seems that it could be quite helpful in reducing phytic acid. We can make our own and simply grind it as needed. If you don’t have your own grain grinder you can just buy a cheap coffee grinder and grind enough to add to your projects. The one study that we read about up above used only 5 to 10% sprouted flour, so it doesn’t have to be a high percentage.
Time (the more the better): Traditional societies often fermented long periods of time and you see that in many studies time did make a difference in phytic acid reducation. An overall rule of thumb is the longer you ferment or soak, the more everything will predigest and break down. It will also often get more sour (just a warning). Generally 24 hours is better, 12 hours acceptable, especially if at cooler temperatures.
Sprouting: As seen above in many of the studies, germination or sprouting was often very effective in reducing phytic acid. If you followed that with fermentation, the results were often even dramatic. Sprouting may be the very best way to reduce phytates in legumes as well.
Partially Milled Grain: Some grains, such as millet or rice may have been partially milled. Both of these grains were naturally low in phytase so by dehulling them, a lot of the phytic acid would be removed. You can sometimes find milled rice (different than white rice), or buy germinated rice.
Do I have all of my questions answered yet? Of course, not. But I am inspired through this research to continue to keep soaking, sprouting and fermenting away and to do so even more carefully!
[i] The Influence of Soaking and Germination on the Phytase Activity and Phytic Acid Content of Grains and Seeds Potentially Useful for Complementary Feeding, Journal of Food Science
Volume 67, Issue 9, pages 3484–3488, November 2002
[ii] Wise Traditions, Vol 11, Number 1, Spring 2010, Living with Phytic Acid by Ramiel Nagel
[iii] [Nutritional changes caused by the germination of legumes commonly eaten in Chile] Camacho L; Sierra C; Campos R; Guzmán E; Marcus D, Archivos Latinoamericanos De Nutrición [Arch Latinoam Nutr] 1992 Sep; Vol. 42 (3), pp. 283-90.
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[vi] Changes in phytates and HCl extractability of calcium, phosphorus, and iron of soaked, dehulled, cooked, and sprouted pigeon pea cultivar (UPAS-120). Duhan A; Khetarpaul N; Bishnoi S, Plant Foods For Human Nutrition (Dordrecht, Netherlands) [Plant Foods Hum Nutr] 2002 Fall; Vol. 57 (3-4), pp. 275-84.
[vii] Antinutrients and digestibility (in vitro) of soaked, dehulled and germinated cowpeas. Nutrition And Health (Berkhamsted, Hertfordshire) [Nutr Health] 2000; Vol. 14 (2), pp. 109-17. Preet K; Punia D
[viii] Antinutritional factor content and hydrochloric acid extractability of minerals in pearl millet cultivars as affected by germination. International Journal of Food Sciences & Nutrition; Feb2007, Vol. 58 Issue 1, p6-17, 12p, 5 Charts, Abdelrahaman, Samia M.1
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[ix] Effect of several germination conditions on total P, phytate P, phytase, and acid phosphatase activities and inositol phosphate esters in rye and barley. Journal Of Agricultural And Food Chemistry [J Agric Food Chem] 2001 Jul; Vol. 49 (7), pp. 3208-15. Centeno C; Viveros A; Brenes A; Canales R; Lozano A; de la Cuadra C
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[xii] Brewer’s yeast efficiently degrades phytate phosphorus in a corn-soybean meal diet during soaking treatment. Animal Science Journal = Nihon Chikusan Gakkaihō [Anim Sci J] 2009 Aug; Vol. 80 (4), pp. 433-7. Chu GM; Ohmori H; Kawashima T; Funaba M; Matsui T
[xiii] The effects of soaking of whole, dehulled and ground millet and soybean seeds on phytate degradation and Phy/Fe and Phy/Zn molar ratios. International Journal of Food Science & Technology; Apr2005, Vol. 40 Issue 4, p391-399, 9p Lestienne, Isabelle1
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[xiv] Enzyme activities of lactic acid bacteria from a pearl millet fermented gruel (ben-saalga) of functional interest in nutrition International Journal of Food Microbiology; Dec2008, Vol. 128 Issue 2, p395-400, 6p, Songré-Ouattara, L.T.1Mouquet-Rivier, C.2 Icard-Vernière, C.2Humblot, C.2Diawara, B.1Guyot, J.P.2 firstname.lastname@example.org
[xv] Effect of sourdough fermentation on stabilization and chemical and nutritional characteristics of what germ, Food Chemistry, Apr 2010, Vol, 119, Issue 3, pages 1079-1089, Rissello, Carlo Giuseppe and others
[xvi] Physicochemical changes of oat seeds during germination, authors, Tian, Binqiang, and others, Food Chemistry, April 2010, Vol 119, Issue 3, Pages 195-1200