Cucumbers Go Soft at 24 Degrees
Small pickling cucumbers, 900 g, from the market stall that only has them for about six weeks a year. I scrubbed them, cut a thin slice off the blossom end of each, because that end carries an enzyme that softens the flesh, and packed them upright into a 2-liter jar with two cloves of garlic, a teaspoon of mustard seed and a head of dill from the garden. Brine at 3.5 percent: 35 g salt dissolved in 1 liter of water, poured over to cover, glass weight on top, loose lid.
Then the weather turned. The kitchen hit 24 °C by day two and stayed there all week. I know perfectly well that cucumbers want 18 to 20 °C at most, but I did not have anywhere cooler, and I hoped. By day four the brine was cloudy and sour-smelling, which is normal. By day six the cucumbers were soft. Not slightly yielding, the way a good half-sour is, but limp, and when I cut one it was hollow in the middle with a translucent, almost slimy interior. Four of the eleven were like this. The rest were borderline. I ate two of the firm ones and composted the jar.
Warm fermentation is the main cause. Above about 22 °C the lactic acid bacteria run fast, but so do the pectin-degrading enzymes and the yeasts, and cucumbers are mostly water held together by pectin. The blossom-end trim helps but does not save you in a heatwave.
Second attempt a week later, same cucumbers, same brine, three changes. First, I stood the jar in a bowl of water with a wet tea towel draped over it, which by evaporation held it at about 20 °C even when the room was 24. Second, I added three grape leaves from the vine on the fence, whose tannins are supposed to help the skins stay crisp. Third, I pulled the jar at day four instead of waiting for full sourness, when the cucumbers were still bright green inside and pleasantly sour, then moved it to the fridge.
That batch was crisp and stayed crisp for three weeks in the fridge. I cannot say whether it was the temperature, the leaves or the shorter ferment, and I am not sure I care. Cold and quick is the summer rule now.