Fermentation Friday: Fermented French Fries


We’ve fallen in love with this recipe and this is the only way I will make fries in the future. My kids inhale these and ask for more, no matter how many I make. They are just like I remember fast food fries to be- crisp on the outside, hot and soft on the inside. And since they’re fried in tallow, I feel good about my kids eating them.

When I developed this recipe, I’d been in a fermenting funk. I was having a hard time coming up with something creative. Don’t get me wrong, I love my sauerkraut and kefirs. But I needed something…. more. Different. Something my kids would love. One of my dear friends, Loztnausten, had a post about making shoestring french fries and one on fermenting fries. I had read it long ago, but I kept on having the ‘too much work’ mantra scroll in my head. Hand-cutting all of those fries…. I wanted a food processor with a blade that could do it for me, but it was out of my budget. If I wanted french fries, I would ask my husband to make them for me as a treat, when I was working a late night and he had some free time and was looking to dote on me by whipping up something special and junky in the kitchen for us to munch on while I slaved away on the computer. Last January my husband made some french fries, using the mandolin slicer I had recently acquired from a friend. He asked me to look up what temp to cook them at, as his last batch had turned out too oil-logged. We knew he needed a higher temperature, so I surfed over to Everything Free Eating to see how LZ does her fries and I again saw the fermented fries post.

A light bulb went off.

The Research

I did a little research. In this paper, fermentation with a lactic acid bacteria (LAB) resulted in a reduction of the acrylamide in french fries by as much as 90% after 15 minutes. Fermenting in an anaerobic environment is the best way to encourage the production of LAB at home so your can achieve this same result without needing a lab coat, a college degree and an industrial process to cook your diner.

Why do we want to reduce the acrylamide? It’s a carcinogen. Anything that browns while it cooks- bread, potatoes, chips, biscuits, pretty much any baked or fried good, forms acrylamide as it browns.

How does LAB fermentation work to reduce the acrylamide? A quote from Science Daily tells us

“Acrylamide is formed as a reaction between the amino acid asparagine and simple sugars such as glucose and fructose. Put simply, the lactic acid bacteria remove these compounds and inhibit the formation of acrylamide.”

If you’d like to read more about how LABs consume these simple sugars, this book is a good place to start studying. The paper mentioned above, Lactic acid fermentation reduces acrylamide formed during production of fried potato products, was published in the journal Aspects of Applied Biology. It says in its summary:

“Lactic acid bacteria (LAB) metabolise simple sugars rapidly, producing lactic acid which lowers pH and reduces the Maillard reactions initiated by heat. This method can be used in industries producing fried potato products to reduce their problems with acrylamide formation. Applying the LAB method to French fries shortly prior to the pre-frying step reduces acrylamide formation as much as 90%. Browning reactions consequently are reduced. Sensory analysis shows loss of colour and burnt smell and taste without affecting quality of final potato sticks. A fermentation time of approximately 15 minutes is needed given a dense LAB culture. The results from large scale industrial- batch as well as continuous experiments – indicate that LAB fermentation provides the best means for acrylamide mitigation in the production of fried potato products.”

The Application

So the research says that LAB thrives best in an anaerobic environment. Anaerobic means that oxygen is not present; aerobic means that oxygen is present. In order to get LABs to proliferate, I needed to provide an anaerobic environment that would encourage their growth while discouraging the growth of all non-beneficial species, especially the aerobic ones.

So, how can be get an anaerobic environment in home fermentation? That can only be accomplished with a seal that prevents oxygen from entering while an airlock allows carbon dioxide to escape. Without an anaerobic environment, the LABs will not flourish and the acrylamides will not greatly diminish. Open air fermentation will not reduce acrylamides to the same extent due to the lack of LABs. As the bacteria produce carbon dioxide and use up the oxygen, it reduces the population of undesirable, aerobic bacteria and allows the LAB to flourish in the oxygenless environment. The Pickl-It provides this type of environment, as it as an airtight seal and an airlock for the growing carbon dioxide to escape. An open bowl provides a continuous supply of oxygen, never increasing the amount of LAB present and giving an environment that is ideal for the undesirable, aerobic bacteria to flourish. A mason jar would not, either, as it has to be burped regularly to allow the building carbon dioxide to escape. Any time you burp a mason jar, it allows oxygen to rush into the vessel, starting the process all over again. Not burping the jar would cause explosions, as I have had happen in the past. An air-tight vessel with an air lock is the only way to see the LABs flourish and therefore reduce the acrylamide in the potatoes.

This makes sense to me. The examples of ancient fermentation crocks I have seen contained wooden lids and were buried while they ferment. A good example is Korean Kimchi. Ditto for the Icelanders and their fermented shark, called Hakarl, which sits in the ground for 6-12 weeks to ferment. You don’t get air circulation under the ground.

You will notice in the study, that the concentration of LABs used to reduce the acrylamide by 90% was a 1% solution. In order to reach a concentration of 1% in your own kitchen, you need your potatoes to be in an environment where oxygen can not enter for 3-6 days, according to the Handbook of Fermented Functional Foods. If you preview this book on Amazon using their Look Inside! feature, you can read about it on page 402 of this wonderful and very detailed book. Other parts of this book are available on Google Books, if you’d like to read the beginning of the book.

The Recipe

Mmmmm… crispy outside, soft inside, and just the right amount of salt!

I had my kids wash some potatoes and using the mandolin slicer, I sliced about 10 potatoes into fries in less than 10 minutes. Do not peel the potatoes before you cut them, as LABs are mainly present on the skin of the produce. I placed my mandolin over a big bowl to catch the fries. When I was done slicing, I covered the fries with cold water and set them aside to soak for about 30 minutes while I washed dishes. This helps draw starch out of the potato. I drained and rinsed them, then placed them into my Pickl-It fermentation vessel.

Once in the Pickl-It, I filled it with a mix of 1-1/2 tsp of salt to each quart of water. I have since learned that the owner of Pickl-It, Kathleen Mills, recommends you use 8 grams of salt to every pound of vegetables, and I will be trying this amount in the future. I placed the dunker on top to make sure the potatoes stay under the water level, closed the vessel and put the air lock in place according to the directions. I sat it in the out of the way place I keep my ferments. All told, it took me about 15 minutes of hands-on time.

Then I walked away for three days.

One of these days, I will learn to not take pictures while running my grain mill. Pardon my dust… and the unmilled bits of rice on the counter!

When I was ready to do my fries, I pulled the air lock off of the vessel, dumped it all into a colander in my sink and then rinsed the fries thoroughly.

I spread them out on a kitchen towel and patted them until dry on all sides. If the fries are not dry when they go into the oil, they will not become crispy.

I took a quart of tallow and placed it into a 2-quart or larger pot. Because oil expands greatly when you fry, you want to fill the pot no more than half full with oil. Make sure you use a heavy-bottomed pot that heats evenly and enough oil that the fries can move freely. I used my Staub enameled cast iron dutch oven. I put it onto the burner on high and using a thermometer, I watched the fat until it came to 400 degrees.

Why tallow? It has a smoke point of about 420 degrees. Coconut oil smokes at 350 and lard at 370 degrees. They will both begin to break down and smoke before hitting the right temp, so tallow it is.

Then I lowered the fries into the hot oil, about one serving at a time. You can drop them in, away from you, by hand, or place them onto a spider or wire skimmer and lower them into the oil. Fry, stirring occasionally, until they reach your happy spot. My happy spot is about 6 minutes when put into 400 degree oil.

Don’t overload the pot or the fries will become soggy from the temperature of the oil dropping too much from the addition of the room temperature fries. You don’t want to see the oil drop below about 350 degrees when you put in the fries. You want crisp, not soggy.

See how much the oil expanded? It really bubbles once you put a batch of fries in. Be sure to not overload your pot! Notice the temp is 355 degrees after I put the batch of fries in. If you add too many fries,the oil will drop to too low temp and make for oil-logged fries.

Allow the oil to return to 400 degrees before you put in your next batch of spuds. That’s it! Easy-peasy, quick, and your kids will be thrilled with the results! Now, I no longer hear “that’s the place we used to get French Fries” when I drive by a certain fast food place anymore. Now I hear “when are you gonna cook the fries fermenting on the counter, mama?”

And I couldn’t be happier.

Fries, fresh out of the oil, sprinkled with some Redmond’s Real Salt

Disclaimer: I receive no commission from any of the links above. I do not receive any commission from Pickl-It, I am simply a happy customer who believes in their product.

4 Responses to “Fermentation Friday: Fermented French Fries”

1. michmom1 says:
March 5, 2011 at 09:24 | edit

I look forward to trying this! How many pickl-it jars, at what size, did you need for fermenting ten potatoes? can this be done with sweet potatoes? do you strain the tallow when done and return to the fridge for the next batch? Thanks!
2. KerryAnn Foster says:
March 5, 2011 at 11:10 | edit

I used two 1-1/2 L jars for the ten small potatoes. That was about 8 servings of fries. Since testing this recipe and doing the pictures, I’ve gone to doing 4 servings at a time in one jar- we have a family of four, but there’s definitely more room in the jar for more fries. I haven’t tried sweet potatoes yet, and I don’t know their levels of acrylamides. I’ll have to put that on my to do list. I do strain the tallow and return it to the fridge in a bowl. I don’t put it in a jar because it hardens and is difficult to get out. I use the batch of tallow multiple times, then I fry fish in it one last time before throwing it away.
3. Lisa says:
March 6, 2011 at 22:00 | edit

I love this post – I just need to get some tallow! got the Pickl-its and I love your explanation of real fermenation…it can be challenging to convince folks that the open bowl and mason jar is just true fermenting.

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I'm KerryAnn Foster. I live in the mountains of Western North Carolina with my husband, Jeff, and our two kids, a teen and a tween. I blog here at Intentionally Domestic (formerly Cooking Traditional Foods). I blog about Paleo, beauty, health, family, homeschool and lifestyle for women in their 30s and beyond. I have over sixteen years of real food and natural lifestyle and health experience.

I am also an It Works! Global Triple Diamond Independent Distributor. I love that crazy wrap thing! I have been extremely happy with how the It Works Products have tightened up my loose skin and healed my stretch marks after losing 179 pounds and having a 10-pound baby.

Read about my journey to health through celiac disease, PCOS, food allergies, obesity, adrenal fatigue and heavy metals.


  1. Tiffani says:

    Where do you get your tallow? I had a hard enough time finding non-hydrogenated lard!
    Tiffani recently posted..Absence

    • KerryAnn says:

      I get mine from a local co-op that orders from a grass-fed farmer. The back of the Wise Traditions journal should point you to some resources. Also, you can try sites like and

  2. Tiffany says:

    Can I make this without the PicklIt if I use an airtight jar?
    Tiffany recently posted..Yogurt in an Igloo

    • KerryAnn says:

      Tiffany, mason jars are not airtight unless they’ve been canned. You have to burp them to release the carbonx dioxide so the jar doesn’t explode, and that allows air to rush in when you loosen it (that’s what replaces the carbon dioxide) and it once again discourages the growth of the LABs. You can ferment them in a jar, but it won’t reduce the acrylamide content like airlock fermentation will.

  3. annie says:

    fascinating post…never knew that french fries can be fermented

  4. Amy Estes says:

    Are tallow and lard the same thing? This recipe sounds awesome!

  5. Nicole says:

    I just bought the jar and I pick up my lard tomorrow! I can not even wait for this!!!!!!! French fries are my weakness! I bet I might make these weekly! 😉 This is awesome!!!!!!

  6. Kathleen says:

    I’ve made these twice so far… but both times when taking the fries out of the jar, they stunk!!! Like really bad cheese! Is this normal? I still cooked them… I don’t have access to tallow yet, so I used bacon fat… and they were very good! … but that initial smell is a bit concerning. 🙂

  7. Jill says:

    Have you ever tried baking the fries? Would this be a healthier alternative, or would the fermentation not be necessary if baking instead of frying?

    • You can bake the fries if you want. I’d dry them, toss with oil, salt and pepper and bake at 350 until crispy stirring once or twice.

      Fermentation is necessary regardless of the cooking method because acrylamide is present in the potatoes regardless of how you cook them.

  8. angela says:

    Hi, just wondering if it’s possible to freeze these between fermenting and baking/frying?

  9. Lori B. says:

    What an amazing article. I am slowly trying to cook healthier for my family. As you said, it can be very expensive to eat healthy. I have never heard of fermenting food but I am anxious to look into it. Your website is really great. As a stay at home mom who homeschools her kids, I am always looking for healthy ideas for our family. Thanks so much for your expertise and ideas.

  10. lydia says:

    Wow, great info! I think you may have just convinced me to get a Pickl-It jar. Interesting thing, a restaurant I worked at long ago, actually soaked their potatoes before baking them – no sure it was for the acrylimides, but it made a dang good baked potato!
    lydia recently posted..Dear America: Please Put the Fat Back in Your Diet

  11. Marti says:

    Hi, I’m wondering if fermenting the potatos would lower the carb count/ glycemic load of the potato because the LAB eats up all of the sugars? If so, my type 1 daughter could have potatoes (and not just any potato=french fries!!) again, and that would be worth any extra effort these may take!! Thanks for the post!

  12. Marti, I spent some time on Google and couldn’t turn up anything specific to potatoes, however I was able to turn up one website that had multiple studies referenced for bread and lactic acid fermentation/sourdough reducing the glycemic load at So if you’re going to test this, I would ferment the fries and then serve them British style with a type of vinegar.

    It seems the internet low-carb forums have discussed it a lot, but finding references for studies was difficult.
    KerryAnn Foster recently posted..Twelve Days of Christmas: Salt Dough Ornaments

    • Marti says:

      Hi KerryAnn!

      Sorry to not reply sooner, but I wanted to pop back in and report that this method DID work for my Type 1 daughter! No insulin spike from the potatos after fermenting them first! I can’t thank you enough!

  13. Soccy says:

    Do you add any whey to the jar before setting it aside to ferment?

  14. Marti says:

    Thanks, KerryAnn!

  15. Yolanda says:

    Do you strain and re-use your tallow for these?

  16. Thank you – Our first batch of fermented fries came out great!! See here:

    Potato chips, not so great. They were crispy and light and bubbled, but tasted weirdly like corn chips. We might try them again if we cut down on the fermentation time.

  17. Jane Casey says:

    That is the most awesome thing I have ever heard. I am going to share this recipe!
    Jane Casey recently posted..Hump-Back Healing – Autism One/Generation Rescue Conference, May 23-27 2012

  18. Laurie says:

    … you are strictly fermenting these to get rid of the acrylamides then….. because you are definitely killing any active cultures by frying or cooking at a higher temp….. do you think it would work to cook at 250 in a convection oven for a while… does anyone know ? or would that kill the little buggers too? 🙂

  19. […] Fermented French Fries My favorite fried food. […]

  20. melvin says:

    first time here…love your site…question?…i thought the acrylamides was the process of browning foods…since your fry the potatoes after the ferment how does that stop the formation of acrylamides


    • Melvin, my understanding is that the acrylamide forms due to the cooking process- it occurs in dry heat but not in boiling. Acrylamide is formed during browning- it’s a reaction with the sugars in the food. You’ll notice that the french fries in the picture above are not browned despite being fully cooked. That’s because the lactic acid bacteria eat the sugars that cause the reaction. So the amount of acrylamide is greatly reduced- depending on how you ferment it, you can reduce the acrylamide formation by as much as 90%.
      KerryAnn Foster recently posted..Fermentation Controversy

  21. Heather says:

    We are super excited about this ferment. We recently ordered our Pickl-It set and this is one of the first things we are going to make. Can’t wait!
    Heather recently posted..Milk Kefir & Water Kefir Grains

  22. […] Fermented French Fries – While french fries are cooked, which destroy the probiotic content of the food, the point of fermenting potatoes is to reduce the cancer-causing acrylamide in prior to frying. […]

  23. Manang says:

    I have long been wanting to try this, so finally I got the time and the gumption (and the heavy duty french fry cutter and a good deep fryer). I thought I’d try to jumpstart the fermentation by dumping in about 1-2 tbsp of whey (from making yoghurt) into the jar (I used 2% brine solution to soak the potatoes in after the initial cold water soak-and-rinse). I think from this afternoon to tomorrow will be a good enough time for fermentation. I will update you once I have the results.

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  29. Debra E says:

    So stinkin’ cool! I used my mandolin to slice up 2 potatoes in less that 5 minutes and they look awesome! I’m so excited because I’ve never made French fries before and I’ve had my eye on this recipe for quite some time.
    I was wondering if this same thing could be done for sweet potatoes?


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