Whole spices, ground spices and the step in between

The points below about buying and using spices are ordered by how much difference they make, not by how often they get repeated.

Why whole keeps and ground does not

The aroma of a spice comes from volatile oils held inside cell structures. Grinding ruptures those structures and exposes an enormous surface area to air, so the aromatics evaporate and oxidise. That is why a jar of ground coriander smells of very little after a year while the seeds still smell of something.

Buying whole and grinding as needed is not fussiness; it is the difference between a spice working and not.

Toasting changes the compounds

Dry toasting whole spices in a hot pan drives off moisture and generates new aromatic compounds through browning. It takes under a minute, and the signal is the smell changing rather than any visible colour.

The part that matters: they burn quickly once they start, and burnt spice is bitter throughout the dish with no way back. Toast, cool, then grind, since grinding while hot produces a paste rather than a powder.

Blooming in fat

Many spice aromatics are fat-soluble, so cooking ground spice briefly in oil extracts far more than stirring it into a watery sauce. This is the step that turns a curry from a dish with spice in it into one that tastes of spice. It happens fast and burns fast, so it is usually done off the highest heat and followed immediately by liquid.

Whole spices bloomed in fat at the start of a dish perfume the oil and then the whole pan.

Buying sensibly

Buy small quantities from a shop with fast turnover rather than large jars that will sit for years. Specialist and ethnic grocers frequently sell better spices in larger bags for less money, which is worth it only if you will use them. Spice blends are convenient and vary enormously between brands, and knowing what is in one tells you how to adjust it.

Whole spices you never grind are no more useful than stale ground ones, so be honest about your habits.

Storing them

Heat, light and air are what destroy aroma, which makes the rack above the hob the worst possible place. Airtight containers in a dark cupboard slow the loss considerably.

At the stove, freezing is reasonable for things you use rarely, particularly ground nuts and seeds whose fats go rancid. Labelling with the date of purchase makes it obvious which jars are decorative rather than functional.

Knowing when to add them

Whole spices early, ground spices in the middle in fat, and delicate ground things such as garam masala near the end. Long cooking mutes fresh aromatics, which is why many dishes get a second, smaller addition at the finish. Fresh chilli, ginger and garlic behave more like vegetables than spices and burn at high heat within seconds.

When a dish tastes dusty rather than aromatic, the spice usually went in dry and stayed dry.

Everything above, in order of what to do first

1. Why whole keeps and ground does not. The aroma of a spice comes from volatile oils held inside cell structures.
2. Toasting changes the compounds. Dry toasting whole spices in a hot pan drives off moisture and generates new aromatic compounds through browning.
3. Blooming in fat. Many spice aromatics are fat-soluble, so cooking ground spice briefly in oil extracts far more than stirring it into a watery sauce.
4. Buying sensibly. Buy small quantities from a shop with fast turnover rather than large jars that will sit for years.
5. Storing them. Heat, light and air are what destroy aroma, which makes the rack above the hob the worst possible place.
6. Knowing when to add them. Whole spices early, ground spices in the middle in fat, and delicate ground things such as garam masala near the end.

The takeaway

Buy whole where you can, toast or bloom in fat, and keep it all away from the hob.

Taste it before it leaves the pan. That is most of cooking.