Choosing Spices to Buy
As a general rule it is always better to buy whole spices and grind the amount you need to order. In certain cases this is not always possible because of geographical or seasonal availability. A good example of this would be turmeric, a wonderful, evocative spice in its fresh form, which is not readily available in the West and sadly loses much of its natural vibrancy during the drying process.
Whole seeds, bark and buds keep their flavour far longer than their powdered counterpart but even so they will also deteriorate over time.
When buying whole seeds look at the colour, they should be bright and fresh looking, with a smell to match. Green cardamom, for example should have a bright green outer husk with shiny black seeds inside, avoid any with faded green/grey shells at all costs. Coriander is another spice which, when fresh has no equal. Try growing a coriander plant and let it run to seed, when the seeds have turned from green to brown pick them and dry them in a warm, dark space and use as soon as possible. The resulting taste and aroma is a powerful citrus like perfume and as far removed from shop bought ready ground as you can get.
In terms of fresh spices such as lemongrass, ginger and galangal I always advocate buying fresh and not dried. There are certain recipes in Asian cookery for example which use dried ginger or chilli powder but for lemongrass and the majority of herbs I fail to see the point. The less said about freeze dried herbs the better as far as I am concerned, it is not a question of food snobbery but of taste. I really cannot see what use dried lemongrass is when the fresh bulbs are available year round and infinitely superior and practical in every way.
Storing Fresh Spices
Any fresh spices bought that are not used straight away should be kept chilled. Fresh chilli, ginger, lemongrass and herbs such as lime and curry leaves should be kept refrigerated in a sealed container. Damp kitchen paper can be used to wrap your herbs in and chillies, lemongrass and ginger will store for up to three weeks in the salad compartment of your refrigerator.
Storing Dried Spices
Always keep dried spices away from the sunlight. Both whole and ground spices will suffer if subject to light, warmth or moisture. I would recommend keeping whole spices in an airtight container preferably in a cupboard in a cool part of the house for a maximum of six months.
Avoid buying spices in bulk, there are a number of wholesale outlets that also sell to the public and offer large bags of chillies and other spices at discount prices. This is all right for the professional caterer who will use such an amount in a relatively short space of time but for the home cook the money saved in the short term will be lost as the spices lose their quality through lack of use. Try small, independent spice stalls at your local markets, there you can buy smaller amounts and they are usually much fresher and competitively priced.
see also Spice Notes