Research and Information

The solution to your moldy nuts

9 comments

Mold! Is this something you should care about or is it just an over-dramatized fad? Is mold in my nuts, seeds and grains? Can nuts make you sick and how do you remove mold from nuts anyways? Are mycotoxins really an issue and where are mycotoxins most commonly found? If you are curious about any of these things just read on for a quick overview and solution to your moldy nuts! And as always this post is all based on peer-reviewed evidence-based research and backed by science.


Wow, There is just so much research on mold in nuts and my nerd brain is both so excited and overwhelmed. Ok some housekeeping, this is a very simplified review of what I discovered after some digging around in the research literature. Even though I have a PhD and am well versed in understanding sound research, I am not an expert on fungi or their biology. That being said the information and suggestions in this post are based on scientific facts and published papers.

THE SKINNY: If you are here just for the solution and not the nerdy stuff let me just leave this here… mold sucks, mycotoxins are worse. While most nuts will be contaminated with mold this does not mean they have mycotoxins present. If you take nothing else from this post it is this: When dealing with nuts and seeds make sure to PICK OVER, RINSE, HEAT, and STORE your nuts and seeds! And when in doubt throw it out! Fresh nuts/seeds are your friend so buy small amounts at a time.

(oh and before you run off be sure to check out this MOLD FREE creamy almond milk recipe, click here)

Moldy nuts, is that a thing?

OK let me start by stating that I eat, and will continue to eat, grains, seeds, and nuts even after writing this post. I am not going to try and freak you out or convince you that you shouldn’t eat food and that everything is going to kill you. That’s just not helpful for anyone! I didn’t discover that the food industry is trying to poison us or has some cover-up scheme. Quite the opposite, there is a lot of research going on behind the scenes addressing this issue. Actually, the intended purpose of this article is to inform you of the dangers of consuming nuts that have been improperly handled and stored and the steps you can take to correct any mishandlings and safely store your food.

I started looking into this when I came across an article one day. Ironically this was when I was eating oatmeal slathered with peanut butter. The article stating that tree nuts, seeds, and grains can foster various microorganisms including toxigenic and pathogenic fungal species, AKA MOLD! Removing the spoon from my mouth and ending my morning meal I tried not to freak out while I quickly hit up goggle! And after coming to the usual conclusion that goggle is not my friend, I went on to read some actual facts published by real scientists regarding mold infestation in our precious peanut butter!

Mold and mycotoxins, and why you should care!

Before delving into the research, let’s clear up some terminology so we can all be on the same page. Mold (or mold) is a fungal species that require moisture to grow and organic material to produce energy. While there are over 100,000 types of mold spores, some of them can synthesize (or make) mycotoxins when under the right condition. When these conditions are met, fungi proliferate (or grow) into colonies and mycotoxin levels become high. While mold on its own can have detrimental effects on our health, the mycotoxins they produce are actually poisonous to humans. Their long term effects include cancer and immune deficiency problems too name a few.

The fungi that produce mycotoxins in food fall into 2 groups: those that invade before harvest (field fungi), and those that invade after harvest (storage fungi). The field fungi disappear after harvest if handled correctly by the producer (by drying them). So field fungi, in theory, should not concern us because we are going to assume that our food is handled properly by the food producer and manufacturer. So what is partially in our control (because this also applies to grocery store shelves and bulk bins) is the storage fungi. That is the fungi we want to eliminate. Fungi growth in this state depends on physical factors, such as moisture (water activity), temperature, and damage as determining factors of whether storage fungi will make an appearance. So these are the things we need to address. But first the low down on mycotoxins…

Why you should care about mycotoxins:

While there are many types of mycotoxins, there are 5 groups that occur in food:

  • deoxynivalenol/nivalenol
  • zearalenone
  • ochratoxin
  • fumonisins
  • alatoxins

The table below summarizes some of the places they are found and their effects on our health (it is not a complete summary by any means and is missing many nuts and grains but you get the idea).

Fumonisins and aflatoxins are of the greatest concern to our health and the most present in grains and nuts (Tournes et al., 2015). Aflatoxins were classified as a class 1 carcinogen by WHO, and interact with the function of the immune system, disrupt the digestive and urinary system, the reproductive systems, nervous system, are mutagenic in bacteria (affect DNA).. pretty much they suck!!

Now before you dismiss this mycotoxin as rare let me just state that many of the research I read found positive results for Aspergillus, the mold that produces mycotoxin, when testing nuts for fungi. Meaning those beloved nuts you eat every day has the potential to produce mycotoxins and make you sick!

mytotoxins in grains and seeds
Table 1. Mycotoxins in staple grains and seeds Taken from Food and Agriculture Organization of the United Nations technical leaflet No. 3

Are mycotoxins really in my nuts/seeds and grains?

I do not need to sell you on the harmful effects of mycotoxins, most people get that they are bad and want to avoid them. So before I freak you guys out anymore I want to say that although mold produces mycotoxins, they are not always a packaged deal. So despite all the terrifying blogs and fear-mongering going on just take a breath. Remember, as I said above in order for mold to produce mytotoxins the right conditions need to be met. In fact, despite the vast reports of positive mold samples from grains, nuts and seed (Abdel-Gawad et al., 1993, Tournes et al., 2015, Jiménez et al., 1991), positive mycotoxin levels are much less common (Abdel-Gawad et al., 1993).

But this is not a green light for enjoying your raw nuts. Rare does not mean zero and we still have the mold spores to deal with! Mold on its own can make you sick! The main idea here is we want to eliminate the possibility that our food ‘may’ contain or eventually produce mycotoxins! Aka remove the mold and there is no chance of encountering mycotoxins!

How does mycotoxins infect my food?

Alright now for some scary before the solution (hang in there with me). The main conclusion I got from researching mycotoxins is that they are almost impossible to eliminate once a portion of food is contaminated with them. However, most of the contamination seems to occur in the field, before the product goes to market. And most of the contaminated food is discarded. However, while our food organizations regulate the number of acceptable mycotoxins in the foods that go to the market, the detection is problematic because aflatoxins are not evenly distributed throughout a bulk shipment.

Actually according to the USDA ” aflatoxins are considered unavoidable contaminants of food and feed, even when good manufacturing practices are followed”. Unavoidable! seriously!?!! You know it’s times like these that I thank my stars that I eat a lot of plants. I won’t even go into the number of mycotoxins in animal feed and cow milk, guys it is scary!! I know one HUGE way I am reducing my exposure is by reducing the number of animal products in my diet.

So what’s the solution here?

What can we do about this, well we know that heat treatment works on mold spores, BUT mycotoxins can not be destroyed by heat. Research on the removal of mycotoxins during food preparation found that cooking, frying, and roasting were unsuccessful at removing mycotoxins from food. Well, that sucks…

Why won’t heat destroy mycotoxins? Because the decomposition temperature of Aflatoxins is 237-306 degrees Celsius (Jalili 2015). While some methods may be better than others (pressure cooking rice can reduce mycotoxins by 78-88 percent) the main conclusion is that the removal of mycotoxins depends on many factors and is extremely hard to eliminate fully.

So the biggest thing we can do to eliminate any mold before it has the chance to produce mycoctoxins! So buy fresh nuts, seeds and grans from a trusted company and store them properly! While this still won’t address possible mycotoxins that may be present in our food this is a huge start. We can not live life-fearing food, our bodies are very good at detoxing and eliminating waste. If you are healthy and have good functioning detox pathways (gut, liver etc) then the odd trace exposure may be fine. The issue arises with large or chronic exposure. In the end, if you are concerned then do not make nuts, seeds, and grains a huge part of your diet. This falls in line with having a well balanced whole food diet anyways!

Is this really an issue? Just how infected are my nuts?

Of the research I came across, when researchers tested samples of nuts, seeds and grains, they almost always found some contamination of mold. The percentages and amount of mold they see vary with each paper and each nut. However, the general idea is that you can almost guarantee you will find some species present. As for which nuts are the worst? It seems like walnuts, peanuts, pine nuts, almonds, and cashews rank high on the board. Tournes er al., (2015 ) found Aspergillus (the mold that can produce the mycotoxin aflatoxin) in all the nut samples he tested. With walnuts and pine nuts testing the highest for both mold and yeast. But remember, mold does not mean mycotoxins… yet!

Now for the good news…

Fungi can not grow or produce mycotoxins in dry foods. So drying and proper storage will be your best friend here! Moisture is your enemy. In addition, we also now know that mold is killed by heat so the removal of mold is actually very simple. Rinse, then heat to dry!

You also want to pay attention to any physical damage as this is a contributing factor to storage fungi. If there is damage to the nut then moisture can get deep within making it harder to fully dry. This is a huge concern for nut butter. Let’s face it, companies will likely use damaged nuts at the bottom of the barrel to ugly to package and sell. However, many brands use dry roasted nuts and seeds and or pasteurization which in theory should destroy any mold present. Plus these nuts and seeds should be fresh which further reduces the possibility of mycotoxins.

OK, so what can we do at home to help reduce our exposure to mold (and possibly mycotoxins) from nuts, seeds, and grains? Here are a few of the procedures suggested by researchers that we can implement fairly easily:

How to remove mold from nuts

THE TAKE HOME MESSAGE: PICK OVER, RINSE, DRY, STORE

1. Handpicking: Carefully inspect your grains and nuts for signs of mold and discard any that look moldy, discoloured or shriveled. Some additional steps you can take are to buy grains and nuts as fresh as possible. Ideally from a local and trusted brand. Reach out to the company and ask them what their procedure is for testing for mycotoxins. How do they prepare and select the nuts and do they pasteurize?

2. Rinsing and soaking: This information was harder to come. What I discovered was that washing can reduce mold and water-soluble mycotoxins by 65-69 percent in some foods. Without boring you to death, the take-home is that this is a good step to take. Even though it won’t eliminate or deactivate all the mold or mycotoxins that may be present. Here is what researchers suggest:

  • Soaking in a 0.1 M solution of water and sodium carbonate for 24-72 hours (the gold standard)
  • A simple water rinse is effective at reducing a good amount of mold spores.

Since the research on this is scarce, recommendations of soaking times per nut or grain just don’t exist yet. And while there are many blogs on the recommended soaking times, I believe these guidelines are based on increasing the nutrient bioavailable and reducing phytic acid and not for mold reduction.

CAVEAT: I will need to do some more research on this but my understanding is that too much water is not a good thing. This is a wake-up call for me because just before writing this I soaked my cashews for like 24 hours… oooops! Remember mold loves moisture! So make sure to under soak rather than oversoak if you are concerned and rinse a lot! The real mold reducer will be heat treatment, aka dehydrating or cooking.

3. Dehydrate: while mycotoxins are heat resistant this will be an important step to reducing mold spores and their ability to proliferate. Remember mold loves moisture so you want to eliminate as much moisture as possible! Again the procedure for dehydrating nuts, seeds, and whole grains are well published (like here). I wouldn’t worry much about the exact procedure but more on getting them as dry as possible! 12 hours at 150 degrees seems like the gold standard.

  • 812EugOu9PL._SL1500_
    The dehydrator I use is from Salton that I got off Amazon (here). It is easy to use, good quality and fairly inexpensive. For our family, this is a good size however we are not over consumers of nuts.

4.Proper storage: After buying good quality nuts, seeds and grains, picking thru, rinsing and drying make sure to not undo your work! You will want to continue to minimize exposure to moisture, temperature fluctuations, and damage. If possible store them in a glass jar in the freezer or a cold dark place.

So the biggest take away is to rinse (or soak) and DRY your nuts, seeds and when possible grains. So that is it for now if you made it this far thanks for reading. There are also debates and research going into nut allergies and mold but that would be for another post. If you are interested in that leave a comment below!

PICK OVER, RINSE, HEAT, STORE

You will also find these nuts and seeds make the best plant-based milk. For a great recipe on making creamy almond milk check out this post, Creamy Almond Milk.

Anyhoo thank you for reading! We are working on more evidence-based research to commonly asked questions so be sure to comment down below if you would like something reviewed. Oh and come check me out over on Instagram and say hello!

And if you want more now be sure to check out these:

Reference:

Abdel-Gawad KM1, Zohri AA.(1993) Fungal flora and mycotoxins of six kinds of nut seeds for human consumption in Saudi Arabia. Mycopathologia. Oct;124(1):55-64.

Burge, H. How does heat affect fungi? Bipolaris species https://www.emlab.com/resources/education/environmental-reporter/how-does-heat-affect-fungi-bipolaris-species/

Kamimura, H. (1989). Removal of mytotoxins during food processing. Mycotoxins and Phycotoxins ’88, Amsterdam: Elsevier Science Publisher pp 169-176.

Karlovsky, P., Suman, M., Berthiller, F., De Meester, J., Eisenbrand, G., Perrin, I., Dussort, P. (2016). Impact of food processing and detoxification treatments on mycotoxin contamination. Mycotoxin Research, 32(4), 179–205. http://doi.org/10.1007/s12550-016-0257-7

Jiménez, M., Mateo, R., Querol, A., Huerta, T., Hernández, E..(1991) Mycotoxins and mycotoxigenic moulds in nuts and sunflower seeds for human consumption.
Mycopathologia Aug;115(2):121-7.

Locksley. Trenholm, H & L. Charmley, Lynne & B. Prelusky, Dan & M. Warner, Robert. (1992). Washing procedures using water or sodium-carbonate solutions for the decontamination of 3 cereals contaminated with deoxynivalenol and zearalenone. Journal of Agricultural and Food Chemistry – J AGR FOOD CHEM. 40. 10.1021/jf00023a021.

Mahoney, N. and Molyneux, R.J., 2004. Phytochemical inhibition of aflatoxigenicity in Aspergillus flavus by constituents of walnut (Juglans regia). Journal of Agricultural and Food Chemistry 52: 1882-1889.

Tournas, V., Niazi, N., & Kohn, J. (2015). Fungal Presence in Selected Tree Nuts and Dried Fruits. Microbiology Insights, 8, 1–6. http://doi.org/10.4137/MBI.S24308

World Health Organization (2018) Department of food safety and zooness. Foodsafety Digest WHO/NHM/FOS/RAM/18.1 (http://www.who.int/foodsafety/FSDigest_Aflatoxins_EN.pdf)

9 Comments

  1. Pingback: Creamy Almond Milk – At my table

  2. Pingback: Zero Waste Food – Earth Mamas International

  3. WOW!! I had no idea! Thanks for the information! You’re a great writer, by the way!

  4. Sofia

    Thank you, very useful and will do exactly this procedure from now on !

    • you are very welcome! Let me know if you want to see any specific posts or topics covered in the future!

  5. Nir Cehn

    Thanks for simplify an in depth review on such misinterpreted topic!
    Untill know my protocol for my nuts and seeds (mostly almonds, peanuts, cashew, california and brazil nuts) was:
    1. A good wash and dry
    2. Put the nuts and seeds into the oven for 15-20 minutes at a relative low heat – 100 celsius degrees, trying to keep the quality of the fats while killing the fungi 🙂
    But according to your review, i think that 15-20 min’ at 100 deg’ celsius isn’t enough to destroy the fungi.

    What yo think about storage the nuts and seeds in the refrigrator?
    It’s not “dry” but on the other way the temperture is very low, maybe at the low Temp’ of the refrigrator the fungi develops at very low rate (like the bacteria).

    Thanks in advance
    Nir Chen

    • Yes fridge or freezer would be great! Also keep in mind if you roast them after you dry them consume quickly as the fats can go bad after a while.

      Like I mention mytotoxins are likely not present but you want to limit the growth of any mold on your nuts. So fridge would definitely be helpful!

      Thanks for your comment

  6. Hi Patricia, would soaking nuts in a solution of water and freshly pressed lemon juice kill fungi, mold and mycotoxins ? Thank you for your research and for considering my question.

    • I don’t believe so. Killing mold usually requires heat or some pretty heavy duty chemicals. But rinsing and heating would.

      If you dont have time to heat, then soak and rinse. That should get ride of most of any mold that may be present.

Leave a Comment

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.