The story goes like this: A few years ago, I was in a program for cooks/chefs and food writers at Audrey Claire’s COOK. One of the chefs who was teaching us was a classically trained French chef (he’s American, but was trained in France and cooks French food at his restaurants). He made this bold claim: No restaurant is making French fries in house, or if they are, their fries are probably not good fries. They’re not doing it, he said, because for French fries to be halfway decent, they have to soak for at least 36 hours, and very few restaurants have room in their walk-ins for the giant vats of soaking sliced potatoes they’d need to fill fry demand. He said he didn’t know why it was such an important step, just that soaking was the only way to do it and achieve worthy results.
I’m generally not down with the word “only” but I was intrigued by his strong feelings on the matter and excited that the process he described was, basically a short ferment. I went home and immediately started playing around with this. The deep-fried Sweet Potato Fry Nests in Ferment Your Vegetables are a result of this revelation. Those party-worthy sweeties are a little sexier, a little more work, and a lot more indulgent than these which are super simple and can easily be added to a weeknight meal.
The best part about these potatoes is the texture. You know the texture of a really great, thick potato chip? Like when they have visible bubbles under the skin and the exact right bite? Think of that transformed into roasted potatoes, with crisp exteriors and smooth, puffy insides. Plus, these potatoes have the added, fermenty advantage of tang and, presumably, somewhat lowered sugar content.
This is my 2nd favorite way to eat potatoes (because mashed potatoes will win any potato contest ever and your arguments are invalid) and I’m excited to share the simple process with you.
Note: In case you missed it, these will not be probiotic after cooking. That loss is a low price to pay for this flavor and texture, IMO.
Crackly Fermented and Roasted Potatoes Recipe
I make these salty because that’s how I like them. If you need to limit salt, you can, just know that you might not get quite the same crisp (and that they won’t taste as good!). I have only tried this recipe with potatoes that I know (or have been told by a generous and knowledgable farmer) are good for roasting, but I done it with several of those varieties and the results have been consistent. If you need help picking a good roasting tater, this post might be helpful.
One other thing on the texture: these are not super creamy. The goodness of this is all about the crusty outer shell, and if they ferment for longer than 5 or 6 days, they can actually get a little hollow on the inside during roasting. I DO NOT MIND THIS AT ALL. I think it’s actually wonderful, but if you’re looking for those dinner home fries that are mostly cream with a teensy bit of crunch, look away. This isn’t the recipe for you.
One other thing on flavor: Fermented for a week or more, they become what my husband calls “tater tarts” because the acidic flavors are quite pronounced at that point. This is my preferred way to eat them, but if you stop fermentation earlier than that, you’ll still get some of those delightfully balancing acids.
Equipment
1/2 gallon jar
Something to weight the potatoes down in the jar
Ingredients
2.5 lbs (1.13 kg) small potatoes, dirt rinsed off in cool water, skins on
2.75 cups filtered water (650 ml)
1.5 – 2 tablespoons kosher salt (27 g – 36 g, or roughly 4.1% – 5.6% in brine by weight)
3 four-inch (100 mm) sprigs rosemary, and more for garnish at roasting time (optional but delicious)
4 peeled cloves garlic, divided (optional)
2 tablespoons (30 ml) olive oil
The How-To
- Quarter or halve potatoes into pieces that are roughly 1.5 inches square. Remove any eyes or greens spots, but again, otherwise keep them unpeeled.
- Mix salt into water until dissolved. Add 2 cloves of garlic into the jar and top with some potatoes. Layer in rosemary sprigs, but end with potatoes on top. Jar should be full to about 1.5 inches below the rim, or to the bottom of the threads.
- Add brine to the jar to just cover potatoes and add your weight. Once the weight is applied, the brine layer should still be 1 inch below the jar rim and no more than half an inch over the potatoes.
- Close or cover jar, according to which type of weight you’ve chosen and ferment at room temp, out of direct sunlight for 4 to 10 days. 4 days will be slightly less crisp, but they’ll have more body. 1o days will be quite sour and have a lot of puff.
- Strain off pickling liquid (feel free to use this for a large pot of soup or anywhere else you’d like salty, sour liquid, but remember it’s VERY salty compared even to normal pickle brine) and pat potatoes dry. Compost the rosemary sprigs and garlic.
- Heat the oven to 400 F and spread the potatoes in a single layer on a large, lined baking sheet. Add peeled garlic cloves and add finely chopped rosemary from another 3-4 inch sprig of rosemary, if using. Drizzle with olive oil and toss to coat. Place it in the oven for 40-50 minutes. They’re ready when they’re deeply browned and have pronounced bubbles under the skin.
- Serve as close to immediately as possible. They will stay kinda crisp in the fridge for a couple days, but they won’t be company ready again.
*Salt quantity in this recipe has been updated to reflect readers’ feedback. I tested it with lower salt and it still crisps up nicely.*
The link to my book (above is an Amazon Affiliate link). That means that if you buy stuff after you click it, I get a small percentage back from any purchases you make. It doesn’t add anything to your purchase and it’s the only way I make money off of blog posts, so I really appreciate when you do that!
Mary Beth Sullivan says
Could these potatoes have changed their starch to resistant starch with the brining? Maybe a question for Tim Steele, the potato hack guru!
Amanda says
Hi Mary Beth,
I don’t know the answer to that, unfortunately!
Tere says
I don’t know if the brining would turn i.t to resistent, but after it’s fermented as long as you want, you could chill it for a couple of hours. That should do it.
L E P says
According to some of the Dr.s that appear on D.r Oz Show, & on those “PBS Pledge Month” shows: Anything fermented, will make carbohydrates either fully or partially resistant. Also they lower the glucose levels in the body & bring a lot of healthy nutrients to the cells of the body. Just passing on some FYI. Bon Appetite.
Catharina Forbes says
Thank you for this recipe! I love potatoes, especially roasted. I put on a batch today and can hardly wait to try them. Since I’m in Canada and use metric, I appreciate that you add metric conversions, however I noticed that 2.75 cups was equivalent to 623 ml instead of 412 ml (I went ahead and used 623ml). I also have your book and love it. Thank you again!
Amanda says
You are correct that it was wrong (actual 650ml). Thanks for the catch, as the other measurements were off as well!
Make sure to adjust your salt accordingly!
Catharina says
Thank you for the update 🙂
I roasted the potatoes for dinner tonight and they were wonderful. This recipe is definitely a keeper!
Amanda says
Thanks, Catharina!
April says
I made these earlier today and they were fantastic! I used bay leaves and garlic powder instead of the rosemary and fresh garlic, and only did a two day ferment as my kitchen stays pretty warm. I think this is going to be how I make home fries from now on. I’ll probably even add this extra step to other potato recipes (especially mashed potatoes) as the flavor payoff is worth it.
Amanda says
Thanks, April! This is the one ferment I can get my extended family to eat 🙂
Sarah says
I made these tonight after a 7 day ferment and though the texture was amazing, they were so salty they were inedible – such a bummer. I followed the recipe precisely, or so I thought…going to try again this week.
Amanda says
Hey Sarah,
Thanks for reporting back. I do definitely like them salt, but I’m honestly getting insanely mixed feedback (from way too salty to not salty enough), so I’m going to update the recipe with a range. It’s great that so many people are making this! Do try again with a lower amount of salt. You can always add salt after, but I definitely want to use enough to slow the ferment and create a crisp potato.
I appreciate the feedback!
Amanda
Chris says
Not all salts have the same potency. For example sample table salt and sea salt side by side, your taste buds will not deceive you =)
Sarah says
Since you are not using a culture starter, when you say “cover or close the jar” do you still mean to have it open and covered by something like cheesecloth, but not a tight jar lid in order to wild ferment?
Amanda says
Hi Sarah, Vegetable fermentation does not require a starter culture (and generally speaking, a starter culture will give you worse results than not using one, IMO & IME). Lactic acid bacteria are on the veggies because they’re in the soil, and their the probiotics you’re trying to cultivate. They prefer airless environments, so no, you definitely don’t want to cover your jar with cheesecloth.
I haven’t every used the Mortier jar, but google tells me it has a water seal. Using the jar according to the instructions that came with it should give you the appropriate airless conditions.
I hope that helps! Let me know if it’s confusing!
Barbara says
I’m curious about the instructions to compost the garlic. Wouldn’t it be good (Delicious even!) roasted with the potatoes?
I’m just getting into fermenting, focusing first on kefir, but I plan to try this recipe soon. Thanks for sharing!
Margit Sage says
I roasted the fermented garlic with the potatoes and it was amazing!
Oldo says
Was curious if the roasting process for these potatoes destroys the probiotic benefit, if they had any from being fermented. Are there recipes for fermented potatoes that retains the probiotics?
Amanda says
Cooking above 90 degrees will likely kill the probiotics, so no, there won’t be any that retain the probiotics. There are lots and lots of ways to get those good bugs into your diet (many on this site). This recipe is employing fermentation for maximum flavor and crisp.
John says
Isn’t the body 98 degrees? By that logic, you’d cook all your probiotics to death. Actually, bacteria die of around 160F
Amanda says
This is something you can definitely research! Different bacteria survive at different temps (cold and hot) even specific species in the lactobacillus genus. Soil bacteria have been found in countless studies to function best at “room” temp and be outpaced by competitors (or die) at sustained periods of time at substantially warmer or substantially cooler temps.
I definitely recommend doing a bit of googling if this interests you!
My point in this post is that if you’re fermenting for probiotic bacteria, this isn’t the best recipe. If you’re fermenting for flavor and texture, it’s a great option. I hope that clarifies.
Casanra says
If you cook them in a dehydrator at or below 115 degrees, you will retain the probiotics.
Barbara Wilson says
Its there any reason to throw out the garlic rather than roasting it with the potatoes? Either way, the recipe sounds fabulous. Thanks for sharing!
Amanda says
It tends to burn to a char before the potatoes are properly roasted. I wouldn’t throw out the garlic or the brine, though! Just not great to roast with the taters.
Barbara says
I see. Thanks. I may try throwing the garlic cloves in for the last 3 – 5 minutes.
Janine Lazur says
I’ve been a fermentation fiend now that Ive discovered it and am excited to try these with my next winter CSA pickup. Thanks! And for your site in general — your encouraging my new kefir “pet” parenting too!
Amanda says
Congrats on joining the club! May your pets bring you a lifetime of happiness (and gut health)!
Barbara says
Help! Advice needed.
This was a HUGE FAIL! After 5 days, my jar was leaking and my potatoes were reeking. The lid was bulging. I opened the jar in the sink, and the liquid foamed up and over the sides of the jar, ending with a thick white foam that stood up about two inches from the top of the jar. There was a black substance on the inside of the jar lid and the liquid that leaked out of the jar into my cabinet was dark. The rotten potato smell was horrible. Some of the potatoes near the top of the jar had soft spots on them. Most of the potatoes looked fine, were still firm, and didn’t seem to stink, though it was hard to tell because my whole kitchen reeked at that point. I was afraid to use any of them, so I threw the whole batch out.
I THINK I followed your directions to the letter, but obviously something went wrong. Do you have any idea whay could have happened? I’d like to try this again, but I’m not sure I could handle another colossal failure. Other than making milk kefir, which I’m still fairly new at, this was my first attempt at fermentation. Not a good way to start the journey. 🙁 Any advice would be greatly appreciated.
Amanda says
Hi Barbara,
So sorry to hear you had trouble! If this is your first time fermenting, one issue could be expectations. Vegetable fermentation has an aroma that I find pleasant and some people hate (think: sauerkraut). The lid should be bulging if you tightened it completely, but hopefully you checked out the link under “equipment” in the recipe where I discuss weighting ferments in detail (I’ve added it to the body of the recipe as well now) so you knew about different ways to weight and close the jar.
If your potatoes weren’t properly weighted and some were above the surface of the brine, they would get soft. They do need to be submerged, so make sure to check out that part of the recipe and the attached link. The other thing that can impact most of the things you mentioned here is salt, although that would be most likely to be an issue if you didn’t use enough salt, and this recipe calls for more salt than the vast majority of my veg ferment recipes, so I don’t think it’s likely to have been the issue in this case.
Sorry you didn’t have a great experience! This is kind of a unique recipe, since it’s cooked after fermentation, so you might enjoy starting with a more traditional pickled veg. Here is a post on basic fermented pickling, and it includes a list of some of the pickle recipes on the site. I always recommend starting with fermented radishes.
Best of luck next time! I promise, it’s easy and you can do it!
Barbara says
Thank you so much for your reply. Now I’m embarrassed: Somehow I missed the part about the lid. I used a glass weight that fit inside the jar and kept the potatoes under the brine, but I screwed the lid on tightly. I really wasn’t expecting the smell. All of the potatoes were submerged, but maybe the soft spots were caused by the gasses that couldn’t escape? Anyway, thanks for your encouragement, suggestions, and the links. I still want to try this recipe, but will start with something simpler.
Again, thanks so much for taking the time to reply.
Margit Sage says
Just made these tonight and out of the oven at 55 minutes they were still soft and not very tasty. After raising the temp to 425F and baking for another 40 minutes or so, they are amazing!
Jim says
I have now made these twice using Yukon Gold potatoes. The first time I fermented for four days; the potatoes were fine but had no special taste. Fermented a batch for seven days and WOW LIKE A COW! Rich sour taste when roasted with olive oil, THANKS for your fermen’taters!!
Debby says
I wonder if I could do this with sweet potatoes….do you think it would work?
Amanda says
Yes! I think I mention in the post that the original recipe is in my book, and it’s a sweet potato recipe. Best of luck!
Shari says
Ohhhh, wonderful. Thanks. I’m trying these with farm fresh – organic potatoes. Will set up in the next few days! Exactly what I was looking for, and a great way to use my rosemary.
Caroline says
Do you think you can use the fermented potato liquid to ferment vegetables (cabbage, carrots, etc.)
Amanda says
I wouldn’t for a couple reasons: 1) I wouldn’t eat the potatoes without cooking them, even after fermentation, because I don’t know if some of the anti nutrients that are contained in raw potatoes will be altered by fermentation or not (that data doesn’t exist as far as I know). They could be, but I don’t have any way of knowing that.
2) There’s no value in using a starter of any kind in vegetable fermentation. If you read the link ed post, you’ll find a link or two citing studies that show an inferior outcome from vegetables fermented with a starter. Mother Nature (and her soil microbes) do it best.
But those are just my opinions and experiences! Enjoy your process!
Wendy D says
Going to use my brine as an organic weed killer around my raised garden beds. Can’t wait to try these once the fermentation cycle is up. Love fermenting veggies. Salsa is my favorite, eat it daily.
Amanda says
Oh, PLEASE tell me how that turns out!
Biggi says
Just wanted to comment on the salt. I read that some people said it was way too salty. The type of salt one uses has a lot to do with the end result. If you use regular table salt it will taste much saltier versus high quality sea salt.
Karon says
I fermented my red potatoes for 10 days and we roasted them today and they are amazing. Would it be safe enough to use half the sold it calls for? We will certainly make these again.
Amanda says
Not for commercial purposes, and the USDA would recommend that you test the pH of anything below 4% salt (Brine, like this, not direct-salted, for which the level would be 2%). I would not generally ferment this recipe below 4% because of crisp, but that might just be me.
I don’t have any problem fermenting in a low-salt environment, but again the USDA would recommend you always test pH at those levels. Keep in mind that 50% of added salt in brine will be in the potatoes, so if you go to 2%, that’s 1% salt.
Danny says
Hello! I tried to make them but after less than 24 hours my potatoes are starting to have brown spots….is it ok?
Amanda says
Hi Danny,
They should be browning while submerged in liquid, since browning is a result of oxidation. I’m not really clear on what you’re describing, as a result.
Bryan says
What a great recipe, thankful I found this! Been fermenting for about a year and still experimenting with new things, looking forward to trying these.
Side question, have you ever tried fermented shredded potatoes with this recipe? Not sure if it would work as it seems the potatoes breakdown (lose its bulk) some as described. I know cooking GREAT shredded hashbrowns is not easy to get a good golden crust on them and soaking is key, thought maybe this is a option to try.
Let me know if you ever tried or if you think potatoes would breakdown too much. I am going to try your potatoes first and go from there, thank you!
Amanda says
I think you’ll be ok! I often spiralize them to make little nests (pretty cute to put on a plate when company’s over) and that works great. I The original recipe for that is in my book, but made with sweet potatoes!
Debbie cowley says
If making these with sweet potatoes would I peel them first or keep the skins on cube and ferment as usual?
Amanda says
Skins on! The bacteria you need are in the peels. If you must have them peeled for cooking/eating, peel first, but cut big strips of peel and put them in the ferment along with the pieces you plan to eat.
Joni says
I’m really excited to have found this recipe! I’ve been working through a lot of food allergies with my daughter, and we’ve had huge success slowly desensitizing her to things by starting with a teeny tiny bit everyday and slowly increasing the amount (like eggs, which would make her break out in a terrible rash but now she can eat two for breakfast!). Well in that journey, I came across someone saying that people with nightshade sensitivities can go through the same process, and it works even better if they’re fermented. I get terrible joint pain from nightshades, but I’m going to try making these fermented potatoes and see if I can’t desensitize my body to them!
Amanda says
Hi Joni,
I truly hope this helps you. I definitely don’t have any personal experience with that or knowledge, but I’ll cross my fingers for you!
If it does work out for you, you might want to try these recipes as well: Green tomatoes, Bell Peppers, This pepper salsa. There are several fermented nightshade recipes in my book, as well.
Amanda
Rose says
How do you think this fermentation process would work for deep fried french fries?
Amanda says
It works for fries. That’s how this whole idea started.
cemile says
How long can we store these in the fridge after fermentation?
Danielle says
I made this once and it was so so so good (I followed the directions and proportions kinda sorta mostly). But I had a friend coming and wanted to make them on the fly so I swung by the store, got the potatoes and threw them in a brine (3Tsalt/1gal distilled) that I keep in my pantry so I have brine ready. And I got results like the poor first-time-fermenter above. NASTY smell, black overspill in my cupboard, and potatoes that, when rinsed in the colander I poured them into, disintegrated on the outsides. Is this just a lack of salt? I’ve used this on-the-fly brine a bunch for all sorts of veggies I have lying around and just don’t want to waste but when I don’t have time to go all in for fancy ferments and it works out fine. Why do potatoes require so much more salt and why are the consequences so gross and so rapid (the deterioration happened on day four)? Thanks so much and adore your site <3
Alexandria Kemp says
I have a question about fermenting vegetables, as I am new: is it possible to can or pasturize my already fermented pickles so that I can store them at room temperature? I live in an apartment with two other roommates, so fridge space is sparse and we dont have any kind of cellar or cool room and I’d like to store my fermented veggies longer term. Thank you!
Amanda says
Hey Alexandria,
Canning is not my area of expertise, but my understanding is that the pH would have to be measured with professional equipment to know that it’s safe to can. In most cases, you would need to add vinegar to get the pH low enough, which does somewhat defeat the purpose of fermenting.
However, storing vegetable ferments at room temp is fine. They will continue to ferment, so you won’t have that flavor on lock the way you would with canning, and the shelf life will never be as long as it is for a “dead” food. Still, it’s totally safe to leave them. They’ll let you know when they’re past their prime.
Sorry I can’t give you a firmer answer on the canning part!
Naomi says
The French chef said they must soak for 36 hours, but did not mention they should be soaked in brine, or did he? I know of at least one restaurant that soaks their fries for a shorter time in cold water. So is it the water soak what does the trick, or is it the salt in the water that does it? My research reveals that a cold-water soak for 30 minutes to overnight removes the troublesome starch on the outside of the potato, which will help the fries achieve the perfect crispness. No salt needed.