Interactive lesson

How long things keep, step by step

Interactive lesson: quality limits and safety limits, the cellar and the crock, jars, dried food and grain, meat, cheese and eggs, signs of spoilage and how to make stores keep longer.

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The whole lesson as text

1. Two kinds of limit

Every keeping time is either a quality limit or a safety limit, and that changes what you do once it has passed.

Quality limit — After the limit, dried fruit, herbs, grain, acid jars and honey lose colour, smell and vitamins, but they aren't dangerous. Check them; eat them if they're fine, or compost them.
Safety limit — After the limit, fresh meat and fish, fresh cheese, milk, eggs and open jars can carry bacteria and toxins you can't see. Throw them out, don't taste them.
Warmth speeds everything up — Every 10 °C (18 °F) warmer, spoilage runs roughly 2–3 times faster. The same potatoes keep for months at 5 °C and for weeks at 20 °C.
Light, air, opening — Light bleaches and destroys vitamins, air darkens food and turns it rancid. When you open a jar, a bag or the crock, air and microbes get in.

Why: Most stores only lose flavour and vitamins after the limit. Meat, dairy, eggs and low-acid jars can be dangerous after the limit without it showing.

A shelf life isn't a date, it's a condition: a table only holds for the temperature, humidity, darkness and closed container in its heading.
The same product in a warm kitchen keeps half as long or less.

2. The cellar and the crock

In a good cellar, sound, unwashed produce of late varieties keeps for months.

Maincrop potatoes — At 4–6 °C and 90–95 % humidity they keep for 5–7 months. Below 3 °C (37 °F) they turn sweet, above 8–10 °C they sprout; green parts and sprouts aren't eaten.
Roots in sand — Carrots and celeriac at 0–2 °C and 95 % humidity keep for 4–6 months. Beetroot, root parsley and parsnips for 3–5 months.
Apples and squash — Winter apples at 0–4 °C keep for 3–6 months. Pumpkins and winter squash want it warmer and drier: 10–15 °C and 50–70 % humidity, 2–6 months.
The crock until spring — Sauerkraut in the crock, in a cellar up to 10 °C (50 °F) and always under brine, keeps until April–May. When the cellar rises above 10 °C, use it up faster or move some into jars.

Why: Cellar keeping times only hold at the right temperature and humidity. Variety is half the keeping time: an early autumn apple keeps for weeks, a winter variety such as Bramley until April.

Horseradish in the cellar at 0–2 °C keeps for 6–10 months, late cabbage for 3–5 months.
Write your varieties in the keeping log and next year choose the ones that keep.