Weights, Lids and the Mold I Should Have Avoided
This is the failure entry, and I am writing it so I stop making the same error. The jar was a mixed one: carrot sticks, cauliflower florets, a few green beans and some sliced onion, in a 3 percent brine, 1-liter jar, loose lid. I did not use a weight because the vegetables seemed packed tightly enough. I checked it on day two and all was well. Then I went away for five days.
When I came back one carrot stick had floated to the surface, half out of the brine, and on its exposed end was a patch of blue-green mold about the size of a thumbnail, with a white fuzzy rim. The brine beneath looked and smelled fine, properly sour. Some people would scrape off the mold and carry on. I do not. Mold on the surface sends filaments below it that you cannot see, and some molds produce compounds that the brine will not neutralize. The whole jar went in the compost and the jar itself went through the dishwasher twice.
Why it happened is not complicated. Vegetables are less dense than brine and they float. Fermentation produces gas, which gets trapped under and between the pieces and lifts them further. Anything that pokes above the surface is sitting in air, and air is where molds grow. Lactic acid fermentation only protects what is under the liquid.
What I use now, and the order I would recommend trying them:
- A glass weight sized to the jar mouth, which sits on top of the vegetables and keeps everything 1 to 2 cm under the brine. The simplest answer and the one I should have used.
- A small freezer bag filled with 3 percent brine, laid over the top. It molds itself to the surface, costs nothing, and if it leaks it leaks brine, not water.
- A whole cabbage leaf folded over the vegetables and tucked down the sides, with the weight on top of it, to catch stray pieces.
- An airlock lid, which keeps new air out but does nothing about pieces that are already floating.
I replaced the batch a week later with a weight, a leaf and an airlock, and checked it every day. It was fine, as it would have been the first time with a small piece of glass. Cost of the lesson: about a kilo of vegetables and some pride.