It really is “The most expensive spice in the world”. Saffron used for culinary purposes is the stigma or style (the female parts) of the Saffron Crocus flower Crocus sativus L. These are the central yellow threads in the flower, and each flower produces only 3 stigmas, which have to be handpicked. It takes 150,000 flowers to produce one kilogram (2,2 lb) of dried saffron, which is why it is so expensive.
The Saffron Crocus belongs to the Family: Iridaceae and is similar to the Autumn Crocus or Meadow Saffron (Colchicum spp). The latter is poisonous and therefore it is not recommended to attempt cultivation of saffron corms yourself, as the two are very easily confused. Botanically, saffron is a triploid, therefore it is sterile and does not produce seed.
Saffron is an ancient spice: it was known to the Sumerians almost 5000 years ago. It is mentioned in the Egyptian Papyrus of Nebseni, in the Ayurvedic Bhavprakash Nikhantu, the Bible, and in Greek and Roman literature. Research (ref. 1) has proven that it did not originate in Western or Central Asia, but probably in Crete.
The stigmas are sold dry, therefore you will see dark orange/red strands just like those in flowers that have dried in your vase. It is also available ground or crushed, but these are more easily adulterated, so it is better to purchase the stigmas. Real stigmas have tips that always remain lighter in colour than the rest of the thread (dyed ones do not have the lighter tips). The powder should always be red, never yellow.
Spanish (La Mancha) saffron is considered the best, while Kashmiri saffron also has a good reputation, but is very difficult to obtain outside India. Iran has also become an intensive producer.
The colour is directly proportional to the aroma and experts (ref. 2) recommend buying a saffron whose colouring strength is indicated. It should be 190 degrees or more (ISO standard, category I).
Most of the imitators have some saffron in it, but is fleshed out with safflower and/or marigold petals, or the yellow stamina (male sexual organ), of the saffron crocus, which do not have any taste of their own. Sometimes the threads are soaked in oil to add weight.
The stigma are soaked in water, milk or alcohol before used in food, to release the flavour and colour. Well-known dishes are paella, bouillabaisse, breyani and “yellow rice” (pulao). It goes particularly well with dairy products and most grains. It has a slightly bitter taste on its own, but taste is greatly influenced by the pairing with ingredients, as well as its cultivation.
As a dye:
This was the primary use centuries ago and the pigments that cause the intensive yellow colour have been isolated and their staining capacity chemically determined. The yellow robes of the Buddhist monks in Tibet and China are saffron-dyed.
Saffron is thought to clear skin, even acne, and is usually applied in the form of a mask. Traditionally it was used by high-born Indian women to impart a golden hue to the skin.
Historically it was used mainly for treating depression. Clinical tests in the Roozbeh Psychiatric Hospital in the Tehran University of Medical Sciences have indicated that it is a safe antidepressant. It can also be used to treat epilepsy, digestive disturbances, asthmatic breathing, fever, etc. These uses should not be attempted without medical advice.
(1) Plant. Syst. Evol., 128, 89, 1977