Pickles
In the other scenarios a bad result is a dish nobody eats. Here a bad result is a jar that makes somebody ill. A pickle is a preservation method rather than a recipe: the salt selects which bacteria live, the acid protects the result, and if those two numbers are wrong the jar is not safe — however good it tastes.
Change them and see
The fermenting band
Between 2 and 5 per cent. Lactic acid bacteria tolerate the salt and most spoilage organisms do not. Fermentation starts, the pH falls, and the jar begins protecting itself.
In order, minute by minute
Not a list of steps but a timeline: each one carries the minute it happens at and the temperature it happens at. Changing the order changes the result, and this shape is why the engine can say so.
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0 minutes
Sterilise the jars with boiling water, wash the vegetables and discard any that are soft.
Fermentation is a race and the starting population decides who wins it. One soft vegetable or an unwashed jar gives the competition a head start. Trim the blossom end, where the enzymes that break down pectin and soften the pickle sit.
What to look for Firm, unblemished vegetables, and a clean jar and lid.
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20 minutes
Dissolve the salt completely in the water and pour the brine over.
Salt only works where it has dissolved. Salt sitting at the bottom leaves the top half of the jar unprotected even when the measurement was right. The brine also draws water out of the vegetables, so the concentration falls a little in the first days — which is why working at the very bottom of the band is a risk.
What to look for No grains left in the water.
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30 minutesCritical point
Keep EVERY piece under the brine. Use a weight.
The entire method depends on creating an oxygen-free environment: lactic acid bacteria live without oxygen and moulds and films do not. A single piece above the brine is outside that protection and will mould — and the mould does not stay on that piece, since what it produces spreads through the brine.
What to look for Nothing touching the surface, and a weight made of glass or something food-safe.
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35 minutes
A week somewhere cool and dark, loosening the lid a little each day.
The lactic acid bacteria turn the sugars in the vegetables into acid and carbon dioxide. The acid drops the pH, and that is what preserves the jar; the gas builds up, and a tightly sealed jar can burst. Between 18 and 22 °C gives the cleanest ferment: warmer is fast and soft, colder is very slow.
What to look for Bubbles, a cloudy brine and a souring smell in the first days are all normal.
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7 days
Once the sourness is where you want it, move it to the fridge or somewhere cold.
Cold slows fermentation rather than stopping it. The pickle goes on changing in the jar, souring further and eventually softening. A pickle is a slowed process rather than a finished product.
What to look for The brine starts to clear and the bubbling eases.
The numbers that decide it
The fermenting band
Read off salt against water, and this is the number the safety check is actually given. Below 2 per cent is not a matter of taste.
100
Vinegar gives both preservation and taste, and also slows the ferment: enough of it turns a fermented pickle into vegetables in vinegar.
1000
The balance of vegetable to brine and the temperature decide the texture. A warm ferment is fast and softens; the tannins in a vine or cherry leaf suppress the enzymes that break down pectin and keep it crisp.
What is happening in the pot
- ideal 0.8–1.5% Salt · 1.41% Right in the window. Flavours sharpen, bitterness retreats, water is held. Held in the system
What happened, why, and what to do
Some of these can be saved and some cannot. Writing up the second kind as though it were the first costs somebody another twenty minutes.
01 Fuzzy, coloured mould on the surface ⌄
Why
Something stayed above the brine, or the jar took in air.
Cannot be saved
Throw the jar away. What you can see is only part of it and what it produces can move through the whole liquid, so skimming is not enough. A thin, flat, white film (kahm yeast) is a different thing and can be lifted off — but anything fuzzy or coloured cannot.
02 The pickles went soft ⌄
Why
The ferment ran too warm, the salt was low, or the blossom end was left on. The enzymes that break down pectin did their work.
Cannot be saved
The texture does not come back. If it is otherwise safe it is edible but never crisp again; next time ferment somewhere cooler and add a leaf.
03 A week in and no bubbles at all ⌄
Why
Too much salt, too cold a spot, or enough vinegar to have stopped the ferment before it started.
Can be saved
Move it somewhere warmer for a few more days. If it never starts, what you have is vegetables in vinegar rather than a fermented pickle: the preservation rests on the vinegar alone, so refrigerate it and eat it soon.
04 The lid has bulged, or the jar is leaking ⌄
Why
The carbon dioxide had nowhere to go. That is usually normal — but a bulging lid on its own does not mean safe.
Can be saved
Loosen the lid somewhere cool with your face away and let the gas out. If it smells off, or the brine smells putrid rather than sour, throw the jar away.
05 It tastes sour, but the pH is unknown ⌄
Why
Taste does not measure acidity. The 4.6 threshold is not a flavour boundary but the line below which Clostridium botulinum cannot grow, and no nose or palate can find it.
Can be saved
Measure it with a strip or a meter. If the jar is going to sit at room temperature for months this is not optional; if you cannot measure, keep it refrigerated and eat it soon.
The safety check does not know the following. That is not the same as nothing being wrong — it means nobody looked, and anything meant to keep at room temperature has to be measured rather than assumed.
- The temperature it is held at
- How long it takes to cool
- pH, the acidity
- Water activity
- Whether raw meat is on the same bench
- Whether anyone is coeliac
This is a model estimate rather than a measurement. How far each threshold behind it has been checked is below; fourteen of the fifteen still have no source on file, and saying so is better than not.
engine 1.0.0 · ruleset 2026.09.1 · confidence medium
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