spanish yoga retreats logo

Our second post on the subject of tsukemono, Japanese pickles, introduces you to the subject of lacto-fermentation


Soured ume plums are an absolute staple in Japan. The small, yellow fruit is part of the genus prunus and though referred to as a plum is more closely related to the apricot. The plums are salted and allowed to ferment before the addition of crumpled red perilla leaves and finally sun-dried


Ume can sometimes be obtained in the West from Korean and Japanese stores when in season, but they are far from ubiquitous. Fortunately you can get fantastic results and comparable health benefits from standard plums. They will taste different. They’re a different fruit. But they are, in my mind, every bit as delicious.


This is an old concept and much has been written about it. What follows is a simple summary for your convenience

What is it?

Fermentation is the microbial transformation of carbohydrates into either alcohol or lactic acid. Both are useful preservatives and have been used for millennia to preserve food

Lacto-fermented foods are pro-biotic, providing health-promoting micro-organisms and their bi-products to benefit not only gut function but also strengthen the immune system and even enhance your mood

Since most fruit and vegetables naturally contain lacto-bacteria, all you have to do is to provide the conditions for these to proliferate in preference to other potentially harmful bugs. Two conditions must be met:


While salt kills most bugs our friendly lacto-bacilli don’t mind a bit of it, though they do mind a lot. So for example, the addition of anything above 7% salt by weight will start to kill our lacto-friends and cure food, but not ferment it. 2-5% salt, on the other hand, will allow lacto-fermentation to get to work on virtually any fruit or vegetable transforming it into something to grace any meal, great or humble

No oxygen

Lactofermentation will only take place in anaerobic (no air) conditions. If your fruit or veg are directly exposed to oxygen they will soon develop mould and harmful bacteria and the whole batch will spoil

There are 3 commonly-used methods for preventing aerobic exposure

  • Salting draws out water to create a brine in which you can keep your fruit immersed with the help of a weight – sliced sauerkraut is usually made this way
  • Or you can mix a brine in which to immerse your veg – this is the method used for fermented whole cabbages, the leaves of which are used to make the Turkish stuffed-cabbage dish Sarma
  • Large pieces of fruit such as plums do very well fermented inside a vacum-seal bag. These are very easily available and guarantee a scrupulously anaerobic environment. When fermenting plums this is, for me, the method of choice

Lacto-Fermented Plums

Keyword lacto-fermentation, pickles, pro-biotic, raw-food, sides, tsukemono, vegan
Prep Time 5 minutes
Fermentation time: +/- 5 days


  • Fermentation crock or sterilized jar with lid
  • OR
  • vacuum zip-lock bag(s)


  • 1 kg plums stoned and halved
  • 20 g non-iodized salt


Sterilize the container and all utensils

  • use a fresh vacu-seal bag
  • or, if you're using a jar or crock or a previously used vacu-seal bag wash these in warm soapy water and allow to air dry, especially in direct sun-light. Jars and crocks can be dried in an oven on the lowest setting. Lids and rubber seals can be plunged in boiling hot water before air-drying

preparing the fruit

  • wash the plums under running water, cut in half and stone
  • in a bowl toss the plums with the salt to cover evenly

vacu-seal bag

  • place in a vacuum seal bag, spaced apart by a couple of inches
  • remove all the air with a pump
  • leave in a warm place to ferment
  • when the fermentation is underway the bag will fill with CO2: burp the bag by opening, resealing and pumping out all the air once again

Jar or crock

  • recipes and ideas for using fresh and dried lacto plums and their skins follw
  • place the salted plums cut-side down in layers
  • weigh them down: I fill sandwich bags with 2-3% brine, tie theem woith a firm knot and place them over the fruit covering all available space so the lid squeezes the bag tightly against the fruit
  • after a couple of days open the jar and press the fruit down so it is well immersed in its developing vinegar and releasing any air pockets at the same time. Replace brine-filled bag, adjusting the water volume as necessary to keep the fruit wholly immersed

Fermentation times

  • At 25-28C this can take around 5 days. Fermentation at higher temperatures is quicker but gives a rather more acrid result. Generally, the slower the fermentation the better the taste
  • As usual the degree of fermentation depends on your taste. I like them sharp but retaining some fruity sweetness. Let your tongue make the decision


  • the plums and their vinegar will continue to ferment. To slow this down:
  • store the fresh lacto-plums in their vinegar in the refrigerator for a month to 6 weeks
  • or sun-dry for 3 days and store without the vinegar in a jar or plastic wrapper. They will stay good potentially indefinitely without refrigertion
  • the vinegar can be stored seperately, preferably refrigerated
  • the skins can be removed and sun or oven dried until crisp, then flaked or powdered to be added as a garnish to raw salads and cooked dishes
  • recipes and ideas for using fresh and dried lacto-plums, as well the vinegar and skins follow later