Learning how to make lacto-fermented fruit will give you access to a secret ingredient used by the world’s top restaurants and chefs. In addition to incredible flavor, lacto-fermented fruits also have numerous health benefits. In this article, we’ll show you exactly how you can make lacto-fermented fruit at home.
For my birthday earlier this summer, The Tyrant got me the perfect gift: The Noma Guide to Fermentation. In case you’ve never heard of it, Noma (a restaurant located in Denmark) consistently competes for consideration as the world’s #1 restaurant.
One not-so-secret ingredient that Head Chef Rene Redzepi attributes to Noma’s incredible success is fermentation. In fact, fermentation is so essential to Noma’s culinary creations that they started an actual “fermentation lab” that’s equal parts kitchen and science lab.
The Noma Guide to Fermentation is essentially everything they’ve learned about fermentation over the past decade cooked down into a single book.
Now, if you follow our website or social media channels, you know that we love fermentation AND eating home-grown fruit.
Thus, the first parts of the book I dove into were all about how Noma makes and uses various lacto-fermented fruits.
Even though the process of lacto-fermenting fruit is fairly simple and straightforward, I’ve already learned a ton from this book…
What is lacto-fermentation?
Lacto-fermentation is shorthand for lactic acid fermentation. Species of bacteria in the order Lactobacillales are known as lactic acid bacteria (LAB). LAB species are found on every fruit and vegetable in the world, in the soil, and throughout the human body (primarily in our digestive systems).
LAB digest carbohydrates and produce lactic acid (which tastes sour to humans) in the process. LAB thrive in salty, acidic, anaerobic (no oxygen) environments — environments which also happen to kill dangerous pathogenic microbes that can make you sick or worse. That’s why human beings have been working with LAB to safely make and preserve food for thousands of years.
You may not realize it, but your eat and drink countless lacto-fermented products. A few examples:
- sourdough bread
- pickled veggies
- fermented dairy products like yogurt, kefir, and cheese
- sour beers
Health benefits of lacto-fermentation
We’ve written in-depth about the health benefits of eating high quality, homemade fermented foods in our article Fermentation: how to tend your microbial garden for better health.
The short of it: human beings have more microbial cells in their body than human cells. Our microbial partners keep us alive, healthy, and working well — both physically and mentally. They also fend off pathogens, helping to keep you from getting sick.
Without our symbiont microbial partners, we humans don’t work well. One great way to inoculate yourself with lots of beneficial LAB microbes is to make and eat lacto-fermented fruit, ideally from your own foraged or homegrown organic fruit.
How to make lacto-fermented fruit
1. The basic ingredients of lacto-fermented fruit
Making lacto-fermented fruit is quite easy. The only ingredients you need for basic recipes are:
Getting the ratio of salt-to-fruit correct is essential for preventing contamination since you want to promote the proliferation of LAB which thrive in a slightly saline, acidic environment where pathogenic microbes can’t live. According to NOMA’s tests, the ideal salt-to-fruit ratio for best flavor, texture, and safety is 2% salt to total weight of fruit.
For instance, if you have 20 ounces of blueberries you want to lacto-ferment, you’ll need to add 0.4 ounces (~11 grams) of salt. We should also add here that you really should have a good kitchen scale if you want to make lacto-fermented fruit (or make good baked recipes, for that matter) to make sure your measurements are precise.
If you start branching out and adding more ingredients to your lacto-fermented fruit, you’ll need to account for the weight of those additional ingredients before measuring and adding your salt. For instance, if you add herbs and honey to the fruit, weigh them all together, then calculate 2% of the total weight to determine how much salt you need.
Make sure you mix all ingredients together in a bowl and scrape all the salt out of the bowl when putting it into your fermentation vessel.
2. Lacto-fermented fruit containers/vessels
You don’t have to have any fancy equipment to make lacto-fermented fruit. For this article, we used the following:
- glass canning jars we already had,
- glass lids with glass shot glasses as weights to hold the fruit down and submerge it as the water extracts from the fruit,
- saran wrap with rubber band to prevent fruit flies or other microbes from coming in (*you may have to “burp” your ferments to let trapped CO2 out).
NOMA uses ziplock bags for their ferments. Perhaps we’re overly cautious, but we don’t like the idea of housing acidic, biologically active foods/liquids inside plastic containers for days at a time. We can’t find any studies that measure the potential leaching of plastic compounds into fermented foods made in plastic containers, but we take the precautionary principle approach in our own kitchen.
Our recommendation when making fermented foods: use either glass, lead-free ceramic crocks, or silicone containers. In fact, we intend to get silicone food storage bags to help take our lacto-fermented fruit game to the next level.
The nice thing about silicone food storage bags is you can remove all the oxygen from your fermentation immediately at the start. When using jars or crocks, you have to wait for the salt to pull enough water from the fruit to submerge it before the fermentation goes anaerobic.
While kahm yeast (pictured above) is not something to worry about, you never want to eat ferments that have mold growing on them (very unlikely unless your ratios or process were off) or ferments that smell foul.
3. Temperature, time, light
The ideal temperature range for fruit lacto-fermentation is between 70-82°F (21-28°C). A ferment will take a little longer to develop at the bottom end of that temperature range; on the warmer end, it will take less time.
How long does it take to lacto-ferment fruit? Usually about 7-10 days, but the exact answer can only be known by daily tastings, e.g. let your mouth inform your decision. Chopped fruit goes faster, usually a little under one week; whole skin-on fruit usually takes over a week.
If not lacto-fermented long enough, your fruit isn’t very interesting — it basically tastes the same as when you started just with some extra saltiness. Fermented too long, and the fruit is too sharp/sour with few of the original fruit notes left.
As NOMA says, “An ideal lacto-fermentation should maintain the essence of the original raw product, but with added acidity, umami, and depth of flavor.”
Don’t place your lacto-fermenting fruit containers in sunlight/sunny windows. Place them in a spot where you won’t forget about them, but that doesn’t get direct sunlight. For us, that’s the ledge above our kitchen sink.
4. Types of fruit to lacto-ferment – and how to use them
Lacto-fermenting a fruit completely transforms its flavor in indescribable yet delightful ways. And each type of fruit is different…
According to NOMA:
“As LAB ferment sugar, the resultant lactic acid mingles with the acids already present in the fruit. Citric acid — most commonly associated with citrus fruits but also found in many other fruits and berries — can be quite tart and almost give off a burning sensation. Malic acid, found in grapes and apples (think of the tartness of a Granny Smith), is much rounder and mouthwatering. Ascorbic acid is sharp and direct, and can be found in all kinds of tropical fruits, from bananas to guava. The interplay of different acids is one of the most interesting and beautiful facets of fermented fruits.”
With larger fruits like plums and peaches, you’ll want to cut the fruit into smaller, bite-sized chunks and remove the pits/seeds prior to fermenting. Smaller fruit with no pits (like blueberries, raspberries, and blackberries) can be left whole to lacto-ferment.
You’ll also notice that the salt is able to draw the water out of cut fruit far faster than whole fruit with skin on. For example, our cut peaches and cherries are completely submerged in their own juices within ~12 hours, whereas it will take several days before whole blackberries or blueberries are submerged.
5. Using lacto-fermented fruit
How do you use lacto-fermented fruit? Let your imagination run wild!
You can pull the whole fruit out of the brine and use it on top of yogurt of milk kefir with a drizzle of honey or maple syrup. You can blend it all together and use it as meat rubs or to baste on corn on the cob — another NOMA idea, which is amazing. (See our article How to make cast iron corn on the cob with lacto-fermented fruit rub.)
There are few dishes you make that won’t be improved visually or flavor wise by the addition of your lacto-fermented fruit.
Note: We don’t mind the small seeds of blackberries or blueberries, but if you do, strain them after blending when making lacto-fermented rubs/sauces with them.
Recipe: Lacto-fermented peach, honey, and purple basil
Once you get the hang of the basics, you can start adding new and interesting ingredients to your lacto-fermented fruit experiments. This year, we had a bumper crop of organic peaches, giving us ample fruit for experimentation.
We also just harvested over 50 pounds of honey from our hive. Lastly, we’re growing a gorgeous ruffled purple basil named ‘Opalescent’ from our favorite organic plant breeder, Frank Morton, at Wild Garden Seed.
Morton describes ‘Opalescent’ thusly: “the fragrance and taste are completely distinct from sweet basil, and the fruity sweetness and cherry-magenta color it imparts to a salad vinegar is unlike any other herb I know. Beautiful beyond belief in a bottle with olive oil.”
What happens when you lacto-ferment tree-ripened organic peaches, honey, and Opalescent purple basil together? An exquisite flavor combination that defies description.
All we can say is we hope you’ll make this recipe and enjoy it as much as we do, eaten as-is or blended into rubs to bring incredible flavors to other dishes.
Lacto-fermented peaches with honey and purple basil
Some of the best flavors of summer combined into one delicious, easy-to-make lacto-fermented recipe. Wonderful strained and eaten as a chilled savory side salad, on top of fish, or blended into a rub for corn on the cob and other dishes.
- 2 cups chopped peaches (about 13 ounces) chopped 3 peaches
- 1 cup loose packed purple basil
- 1/2 tablespoon pink Himalayan sea salt (exact qty: 4.2 grams)
- 1 tablespoon honey
Chop peaches into bite-sized chunks. Remove basil leaves from stems. Weigh peaches, basil, and honey then calculate 2% of total weight to determine exact amount of salt needed. Stir in salt.
Add mixture to fermentation vessel (see options in article). Start sampling daily around Day 4 to determine when ideal flavor achieved, ours took 6 days at a temperature between 70-72 degrees F.
Refrigerate to slow fermentation, or freeze to stop fermentation. Ingredients can be strained from brine and served as topping or chilled side salad. Or all ingredients (including brine) can be blended together to make rubs or sauces.
Let us know what fruit you lacto-ferment in your kitchen and how you use it!
Get fermenting with other articles from Tyrant Farms:
- Beginner’s guide to making sauerkraut
- How to make quick-pickled daikon radishes (and other veggies)
- How to make the best homemade milk kefir
- Fermentation: how to tend your microbial garden for better health
- How to make elderflower kombucha
- Easiest turmeric and ginger bug recipes
- Turning edible wild flowers into sparkling cordials
- Recipe: chickweed wine? Yes, and it’s really good!
- Tony & Andrea’s pumpkin champagne recipe
- Tepache recipe: how to turn pineapple skins into a delicious probiotic drink