A spice does not expire — it fades. Essential oils oxidise on contact with air, light bleaches colour and aroma, heat accelerates both. A top-grade black pepper stored badly tastes, after six months, like a supermarket grind.
Four enemies in order of damage: oxygen, light, heat, humidity. The fifth, rarely discussed: frequent opening. Each time you break the seal on a whole-spice jar, the aromatic headspace escapes.
Practical rules:
Keep whole, grind on demand. Ground coriander loses 40 % of its aromatic oils within three months; whole coriander, under 10 %.
Glass with a tight lid beats plastic. Metal tins work if food-grade and unlined. Transparent glass only if stored in a cupboard — never on a windowsill or above a stove.
Label the fill date. Most whole spices hold flavour 18 to 24 months; ground spices, six to twelve. Throw out what has faded; no amount of toasting revives an oxidised spice.
Buy small. A farmer's lot of 50 g used within six months beats a 500 g catering bag emptied over three years. Fresh is a variable, not a label.