Turmeric probably originated in Southeast Asia but was carried far and wide in prehistoric times. Today it is most used in India where the majority of dishes contain at least some. In India it is most used dried and ground to a powder before using, but in Southeast Asia it is often used fresh. Turmeric leaves are also used in some recipes.
The intense yellow-orange color of fresh turmeric will stain all your
kitchen equipment and cutting boards bright yellow, but it is not at all
permanent and fades very quickly exposed to sunlight. Turmeric is now
being studied as one of the most powerful natural anti-cancer substances
and for treatment of Alzheimer's disease. Java Turmeric looks the same, but
is said to have stronger medicinal properties.
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Fresh white turmeric is used in Thailand and Indonesia as an aromatic
vegetable. It is milder than yellow turmeric and doesn't present the
staining problem. Dried it is more bitter and must be used sparingly.
Turmeric leaves are also used in some recipes. In India it is used as a
flavoring in pickles. Medicinally it is used in China and Japan and also
in perfumes and liquors. It can often be found in markets serving an
Indian community, sold alongside fresh yellow turmeric and can be frozen
for longer storage.
These notes apply to both Yellow and White Turmeric. Turmeric rhizomes sprout very readily indoors, but do not thrive outdoors here in Southern California because the weather is just too cool much of the year and the air is way too dry. I'm going to try raising it as an indoor plant.
Buying & Storing: When buying turmeric powder try to get it from a market serving an Indian community or from some other high volume vendor. That purchased from supermarkets in tiny jars often has color but less flavor than sawdust. Recently ground turmeric from an Indian market is far and away superior. Fresh turmeric (both yellow and white) can now often be found in markets serving Indian communities - at least here in Southern California. Whole dried turmeric rhizomes are also available.
Fresh turmeric will keep for weeks just sitting in the potato bin at room temperature, but for longer storage, freeze it.
Cooking: Fresh turmeric is often called for in Southeast Asian recipes - generally grated and/or pounded to a pulp. Yellow Turmeric will stain your kitchen equipment something awful - but the stain will be all gone in a few days because it's not light or oxygen stable. You can substitute ground turmeric in most recipes without too much loss of flavor.