Rescues · TO CAN
Cloudy liquid in a vegetable jar.
Why it happens
Sometimes starch or hard water, sometimes spoilage. Cloudiness alone is not diagnostic, which is why the smell and the seal matter more.
Recovering it
A jar that failed to seal within twenty-four hours can be reprocessed with a fresh lid, or simply refrigerated and used. Anything suspected of spoilage is discarded unopened and untasted — the usual kitchen instinct to check by smelling or tasting is exactly wrong here. Follow tested times and pressures rather than adapting a recipe, since the processing schedule is calculated for a particular density and acidity and cannot be reasoned about by feel.
The mechanism
Canning is the one kitchen technique where the safety margin is not a matter of taste, and the reason is Clostridium botulinum. Its spores survive boiling water indefinitely and germinate in exactly the conditions a sealed jar provides — no oxygen, moisture, moderate temperature. What determines the method is acidity. Below pH 4.6 the spores cannot germinate, so high-acid foods — most fruit, properly acidified tomatoes, anything in a vinegar brine — are safe processed in a boiling water bath at 100°C. Above pH 4.6, which covers all vegetables, meats, and unacidified tomatoes, boiling water is not sufficient at any duration, and a pressure canner reaching about 116°C is required. The seal itself is formed by physics rather than by the lid: heating drives air out, and as the contents cool and contract they pull the lid down.
The full TO CAN lesson — how to tell, where to practise it, what it carries to.