Saffron is a spice derived from the flower of the saffron crocus (Crocus sativus), a species of crocus in the family Iridaceae. The flower's three stigmas (the distal ends of the plant's carpel’s, or female reproductive organs) and parts of its style (a stalk connecting the stigmas to the rest of the plant) are often dried and used in cooking as a seasoning and coloring agent. Saffron, which has for decades been the world's most expensive spice by weight, is native to Southwest Asia. It was first cultivated in the vicinity of Greece.
Saffron is characterized by a bitter taste and a hay-like fragrance; these are caused by the chemicals picrocrocin and safranal. It also contains a carotenoid dye, crocin that gives food a rich golden-yellow hue. These qualities make saffron a much sought-after ingredient in many foods worldwide. Saffron also has medicinal applications.
The word saffron originated from the 12th century Old French term safran, which derives from the Latin word safranum. Safranum is also related to the Italian zafferano and Spanish azafrán. Safranum comes from the Arabic word asfar (ÃóÕúÝóÑ), which means "yellow", via the paronymous za‘faran (ÒóÚúÝóÑóÇä), the name of the spice in Arabic.
  
1 Biology
2 Cultivation
3 Chemistry
4 History
4.1 Greco-Roman
4.2 Asian
4.3 Post-Classical European
5 Usage
5.1 Culinary
5.2 Medicinal
5.3 Coloring and perfumery
6 Modern trade
7 Grading

Biology
The domesticated saffron crocus C. sativus is a fall-flowering perennial plant that is unknown in the wild. It is a sterile triploid mutant of the eastern Mediterranean fall-flowering Crocus cartwrightianus. Botanical research indicates that C. cartwrightianus originated in Crete, not in Central Asia as once generally believed. The saffron crocus was the subject of artificial selection by growers who bred for abnormally long stigmas. Being sterile, the saffron crocus' purple flowers fail to produce viable seeds. Because of this, its reproduction is entirely dependent on human assistance: the corms (underground bulb-like starch-storing organs) must be manually dug up, broken apart, and replanted. A corm survives for only one season, and reproduces by division into up to ten "cormlets". The corms then grow into new individual plants. The corms appear as small brown globules, up to 4.5 centimeters in diameter, each shrouded in a mat of parallel fibers.
After a period of dormancy (aestivation) in the summer, five to eleven narrow and nearly vertical green leaves emerge from the ground. These leaves can grow up to 40 cm long. Later, in autumn, purple buds develop. Only in October, after most other flowering plants have released their seeds, does the saffron crocus suddenly develop its brilliantly-colored purple flowers. These can range from a light pastel shade of lilac to a darker and striated mauve. Upon flowering, the saffron crocus remains, on average, less than 30 cm in height. Inside each flower is a three-pronged style terminating in three crimson stigmas. These stigmas may measure anywhere from 25 to 30 mm in length
 
Cultivation
The saffron crocus thrives in climates similar to that of the Mediterranean marquis. Thus, it flourishes in such places as the North American chaparral, where hot, dry breezes blow across arid and semi-arid lands in the summer. Nevertheless, the plant can tolerate cold winters, surviving frosts as cold as -10°C and short periods of snow cover. If it is not grown in a high-rainfall environment, the saffron crocus needs irrigation. For example, in Kashmir, annual rainfall averages 1000–1500 mm, and so Kashmiri saffron is grown without irrigation when rainfall is normal. In the much drier saffron-growing regions of Greece, where rainfall averages 500 mm, and Spain, where it averages 400 mm, irrigation is required. The saffron crocus thrives in spring rains which are followed by relatively dry summers. However, rains falling immediately before flowering cause high saffron yields. On the other hand, rain or cold weather occurring during flowering promotes disease. Constantly damp and hot conditions also harm saffron yields, as do the digging actions of rabbits, rats, and birds. Parasites such as nematodes, leaf rusts, and corm rot also pose threats to saffron crocus harvests. Planting is best done in fields that slope towards the south, maximizing the crocuses' exposure to the sun. Saffron plants need strong direct sunlight and do not thrive as shade plants. In the Northern Hemisphere, planting is done in June. The corms are planted 7 to 15 cm beneath the surface of the soil. Harvest yield and quality are affected by the climate, planting depth, and corm spacing. Mother corms that are planted more deeply yield fewer flower buds and daughter corms, but produce higher-quality saffron. In the conditions found in Italy, planting the corms 15 cm beneath the surface produces optimal saffron threads, while a shallower planting of 8–10 cm yields the most flowers and daughter corms. In Italy, the corms are planted 2–3 cm apart. Optimal planting practices vary widely between Italy, Greece, Morocco, and Spain.
The crocuses grow best in friable, loose, low-density, well-watered, and well-drained clay-calcareous soils with high organic content. Raised beds are traditionally used to promote good drainage. Historically, the organic content of soil for saffron cultivation was boosted with the application of some 20–30 tons of manure per hectare. Afterwards, corms were planted, and no further manure application was needed thereafter a period of dormancy through the summer, the corms send up their narrow leaves and begins to bud in autumn. Only in October (in the Northern Hemisphere) do the plants begin to flower. Harvesting of flowers is by necessity a speedy affair. Upon their flowering at dawn, the flowers quickly wilt under the noonday sun. In addition, all saffron crocus flowers bloom within a narrow window of one to two weeks.

Chemistry
Saffron contains in excess of 150 volatile and aroma-yielding compounds. It also has many nonvolatile active components, many of which are carotenoids, including zeaxanthin, lycopene, and various α- and β-carotenes. However, saffron's golden yellow-orange color is primarily the result of α-crocin. This crocin is trans-crocetin di-(ß-D-gentiobiosyl) ester (systematic (IUPAC) name: 8,8-diapo-8,8-carotenoic acid). This means that the crocin underlying saffron's aroma is a digentiobiose ester of the carotenoid crocetin. Crocins themselves are a series of hydrophilic carotenoids that are either monoglycosyl or diglycosyl polyene esters of crocetin. Meanwhile, crocetin is a conjugated polyene dicarboxylic acid that is hydrophobic, and thus oil-soluble. When crocetin is esterified with two water-soluble gentiobioses (which are sugars), a product results that is itself water-soluble. The resultant α-crocin is a carotenoid pigment that may comprise more than 10% of dry saffron's mass. The two esterified gentiobioses make α-crocin ideal for colouring water-based (non-fatty) foods such as rice dishes. The bitter glucoside picrocrocin is responsible for saffron's flavor. Picrocrocin (chemical formula: C16H26O7; systematic name: 4-(β-D-glucopyranosyloxy)-2,6,6- trimethylcyclohex-1-ene-1-carboxaldehyde) is a union of an aldehyde sub-element known as safranal (systematic name: 2,6,6-trimethylcyclohexa-1,3-dien-1- carboxaldehyde) and a carbohydrate. It has insecticidal and pesticidal properties, and may comprise up to 4% of dry saffron. Significantly, picrocrocin is a truncated version (produced via oxidative cleavage) of the carotenoid zeaxanthin and is the glycoside of the terpene aldehyde safranal. The reddish-colored zeaxanthin is, incidentally, one of the carotenoids naturally present within the retina of the human eye.
When saffron is dried after its harvest, the heat, combined with enzymatic action, splits picrocrocin to yield D-glucose and a free safranal molecule. Safranal, a volatile oil, gives saffron much of its distinctive aroma.Safranal is less bitter than picrocrocin and may comprise up to 70% of dry saffron's volatile fraction in some samples. A second element underlying saffron's aroma is 2-hydroxy-4,4,6-trimethyl-2,5-cyclohexadien-1-one, the scent of which has been described as "saffron, dried hay like". Chemists found this to be the most powerful contributor to saffron's fragrance despite its being present in a lesser quantity than safranal. The glycoside crocin is water-soluble, and so it does not as readily contribute its yellow colouring to oily substances. As such, it is ideal for coloring water-based foods, such as rice. Dry saffron is highly sensitive to fluctuating pH levels, and rapidly breaks down chemically in the presence of light and oxidizing agents. It must therefore be stored away in air-tight containers in order to minimize contact with atmospheric oxygen. Saffron is somewhat more resistant to heat.

History
The history of saffron cultivation reaches back more than 3,000 years. The wild precursor of domesticated saffron crocus was Crocus cartwrightianus. Human cultivators bred wild specimens by selecting for unusually long stigmas. Thus, a sterile mutant form of C. cartwrightianus, C. sativus, emerged in late Bronze Age Crete. Experts believe saffron was first documented in a 7th century BC Assyrian botanical reference compiled under Ashurbanipal. Since then, documentation of saffron's use over the span of 4,000 years in the treatment of some 90 illnesses has been uncovered. Saffron has been used as a spice and medicine in the Mediterranean region since then, with usage and cultivation slowly spreading to other parts of Eurasia as well as North Africa and North America. In the last several decades, saffron cultivation has spread to Oceania.

Greco-Roman
Minoans portrayed saffron in their palace frescoes by 1500–1600 BC, showing saffron's use as a therapeutic drug. Later, Greek legends told of sea voyages to Cilicia. There, adventurers hoped to procure what they believed was the world's most valuable saffron. Another legend tells of Crocus and Smilax, whereby Crocus is bewitched and transformed into the original saffron crocus. Ancient Mediterranean peoples — including perfumers in Egypt, physicians in Gaza, townspeople in Rhodes, and the Greek hetaerae courtesans — used saffron in their perfumes, ointments, potpourris, mascaras, divine offerings, and medical treatments.
In late Hellenistic Egypt, Cleopatra used saffron in her baths so that lovemaking would be more pleasurable. Egyptian healers used saffron as a treatment for all varieties of gastrointestinal ailments. Saffron was also used as a fabric dye in such Levant cities as Sidon and Tyre. Such was the Romans' love of saffron that Roman colonists took their saffron with them when they settled in southern Gaul, where it was extensively cultivated until Rome's 271 AD fall. Competing theories state that saffron only returned to France with 8th century AD Moors or with the Avignon papacy in the 14th century AD.

Asian
Saffron-based pigments have been found in 50,000 year-old depictions of prehistoric beasts in what is today Iraq. Later, the Sumerians used wild-growing saffron in their remedies and magical potions. Saffron was thus an article of long-distance trade before the Minoan palace culture's 2nd millennium BC peak. Saffron was also honored in the Hebrew Song of Solomon. Ancient Persians cultivated Persian saffron (Crocus sativus 'Hausknechtii') at Derbena and Isfahan by the 10th century BC. At such sites, saffron threads were woven into textiles, ritually offered to divinities, and used in dyes, perfumes, medicines, and body washes. Thus, saffron threads would be scattered across beds and mixed into hot teas as a curative for bouts of melancholy. Non-Persians also feared the Persians' usage of saffron as a drugging agent and aphrodisiac. During his Asian campaigns, Alexander the Great used Persian saffron in his teas, rice, and baths as a curative for battle wounds. Alexander's troops mimicked the practice and brought saffron-bathing back to Greece.
Theories of saffron’s arrival are in South Asia conflict. Traditional Kashmiri and Chinese accounts give arrival dates between 900–2500 years ago[36][37][38]. Meanwhile, many historians studying ancient Persian records date the arrival to sometime prior to 500 BC. They attribute this to either Persian transplantation of saffron corms to stock new gardens and parks or to a Persian invasion and colonization of Kashmir. Phoenicians then marketed Kashmiri saffron as a dye and a treatment for melancholy. From there, saffron use in foods and dyes spread throughout South Asia. For example, Buddhist monks in India adopted saffron-colored robes after the Buddha Siddhartha Gautama's death.
 Historians believe that saffron first came to China with Mongol invaders by way of Persia. Yet saffron is mentioned in ancient Chinese medical texts, including the Pun Tsao ("Great Herbal") pharmacopoeia (pp. 1552–78), a tome dating from around 1600 BC (and attributed to Emperor Shen-Ung) which documents thousands of phytochemical-based medical treatments for various disorders. Yet around the 3rd century AD, the Chinese were referring to saffron as having a Kashmiri provenance. For example, Wan Zhen, a Chinese medical expert, reported that this habitat of saffron is in Kashmir, where people grow it principally to offer it to the Buddha." Wan also reflected on how saffron was used in his time: "The [saffron crocus] flower withers after a few days, and then the saffron is obtained. It is valued for its uniform yellow color. It can be used to aromatise wine."

Post-Classical European
In Europe, saffron cultivation declined steeply following the Roman Empire's fall. Saffron was reintroduced when Moorish civilization spread to Spain, France, and Italy. During the 14th century Black Death, demand for saffron-based medicine skyrocketed, and much saffron had to be imported via Venetian and Genoan ships from southern and Mediterranean lands such as Rhodes. The theft of one such shipment by noblemen sparked the fourteen-week long "Saffron War". The conflict and resulting fear of rampant saffron piracy spurred significant saffron cultivation in Basel, which grew prosperous. Cultivation and trade then spread to Nuremberg, where epidemic levels of saffron adulteration brought on the Safranschou code, which fined, imprisoned, and executed saffron adulterers. Soon after, saffron cultivation spread throughout England, especially Norfolk and Suffolk. The Essex town of Saffron Walden, named for its new specialty crop, emerged as England's prime saffron growing and trading center. However, an influx of more exotic spices — chocolate, coffee, tea, and vanilla — from newly-contacted Eastern lands caused European cultivation and usage of saffron to decline. Only in southern France, Italy, and Spain, did significant cultivation endure. Europeans brought saffron to the Americas when immigrant members of the Schwenkfelder Church left Europe with a trunk containing saffron corms; indeed, many Schwenkfelders had widely grown saffron in Europe. By 1730, the Pennsylvania Dutch was cultivating saffron throughout eastern Pennsylvania. Spanish colonies in the Caribbean bought large amounts of this new American saffron, and high demand ensured that saffron's list price on the Philadelphia commodities exchange was set equal to that of gold. The trade with the Caribbean later collapsed in the aftermath of the War of 1812, when many saffron-transporting merchant vessels were destroyed. Yet the Pennsylvania Dutch continued to grow lesser amounts of saffron for local trade and use in their cakes, noodles, and chicken or trout dishes. American saffron cultivation survived into modern times mainly in Lancaster County, Pennsylvania.
 
Usage
Saffron is one of the three essential ingredients in the Spanish paella valencians, and is responsible for its characteristic brilliant yellow coloring.
Saffron is widely used in Arab, Central Asian, European, Indian, Iranian, and Moroccan cuisines. It contributes a distinctive aroma that has been described by connoisseurs as reminiscent of metallic honey with grassy or hay-like notes, while its taste has been noted also as hay-like and yet somewhat bitter. Saffron contributes a luminous yellow-orange coloring to foods. For these traits, saffron is used in baked goods, cheeses, confectionaries, curries, liquors, meat dishes, and soups. Saffron is used in many cultures as a condiment for rice (giving "saffron rice"). In the cuisine of Spain, it is used in many famous dishes such as paella valencians, which is a spicy rice-meat preparation, and the zarvela fish stews.[52] It is also used in fabada asturiana. Elsewhere, saffron is needed in the French bouillabaisse, which is a spicy fish stew from Marseilles, and the Italian risotto alla milanese.
Iranians use saffron in their national dish, chelow kabab, while Uzbeks use it in a special rice dish known as a "wedding plov" (cf. pilaf). Moroccans use it in their tajine-prepared dishes, including kefta (meatballs with tomato) , mqualli (a citron-chicken dish), and mrouzia (succulent lamb dressed with plums and almonds). Saffron is also central in chermoula herb mixture, which flavors many Moroccan dishes. Indian cuisine uses saffron in its biryanis, which are spicy rice-vegetable dishes. An example is the Pakki variety of Hyderabadi biryani. It is also used in Indian milk-based sweets[4] such as gulab jamun, kulfi, double ka meetha, and "saffron lassi", which is a spicy Jodhpuri yogurt-based drink.
Because of its high cost, dishes traditionally made with saffron often use more economical substitutes such as safflower (Carthamus tinctorius) or turmeric (Curcuma longa). Both mimic saffron's color well, but have very different flavors. Turmeric and safflower are also used to dilute saffron. Saffron is also used in the confectionary and liquor industries; this is its most common use in Italy. Chartreuse, gin, izarra, and strega are types of alcoholic beverages that rely on saffron to provide a flourish of color and flavor. 
Italian risotto traditionally relies on the high α–crocin content of saffron threads to give the dish a warm golden-yellow hue.
Experienced saffron users often crumble and pre-soak threads for several minutes prior to adding it to their dishes. For example, they may toss threads into water or sherry and leave them to soak for approximately ten minutes. This is necessary for the extraction of saffron threads' color and flavor into the liquid phase, although powdered saffron does not require this step. Afterward, the soaking solution is added to the cooking dish. Such a step, which allows even distribution of saffron's color and flavor throughout a dish, is particularly important when preparing baked goods or thick sauces.

Medicinal
Saffron's traditional folkloric uses as an herbal medicine are legion. It has been used for its carminative and emmenagogic properties, for example. Saffron was also used against diseases such as respiratory infections such as coughs and common colds, scarlet fever, smallpox, and cancer. It was also used to treat respiratory problems related to hypoxia and asthma. Other disorders that saffron was reputed to counter were blood disorders, insomnia, paralysis, heart diseases, flatulence, stomach upsets and disorders, gout, chronic uterine hemorrhage, dysmorrhea, amenorrhea (absence of menstrual period), baby colic, and eye disorders. Saffron was also an aphrodisiac, a general-use antidote against poisoning, a digestive stimulant, and a tonic for dysentery and measles. Saffron's yellowish hue was also taken as a sign by those who subscribed to the archaic "Doctrine of Signatures" as a cure for jaundice.
Saffron's carotenoids have been shown in scientific studies to have anticarcinogenic (cancer-suppressing), anti-mutagenic (mutation-preventing), and immuno-modulating properties. The active ingredient behind these effects has been identified as dimethyl-crocetin. This compound counters a wide spectrum of both murine (rodent) tumors as well as human leukemia cancer cell lines. Saffron extract also delays ascites tumor growth, delays papilloma carcinogenesis, inhibited squamous cell carcinoma, and decreases the incidence of soft tissue sarcoma in treated mice. Researchers theorise that such anticancer activity can be best attributed to dimethyl-crocetin's disruption of the DNA binding ability of proteins, as shown in Thymidine-uptake studies. Specifically, the DNA-binding ability of enzymes known as type II topoisomerases within cancer cells is inhibited. Thus, the malignant cells are unable to synthesize or replicate their own DNA.

A saffron crocus flower.
Saffron's resultant pharmacological effects on malignant tumors have been well documented in studies done both in vitro and in vivo. For example, saffron extends the lives of mice that are intraperitoneally impregnated with transplanted sarcomas, namely samples of S-180, Dalton's lymphoma ascites (DLA), and Ehrlich ascites carcinoma (EAC) tumors. Researchers followed this by orally administering 200 mgs of saffron extract per each kg of mouse body weight. As a result, the life spans of the tumor-bearing mice were extended to 111.0%, 83.5%, and 112.5% respectively in relation to baseline spans. Researchers also discovered that saffron extract exhibits cytotoxicity in relation to DLA, EAC, P38B, and S-180 tumor cell lines cultured in vitro. Thus, saffron has shown promise as a new and alternative treatment for a variety of cancers.
Besides wound-healing and anti-cancer properties, saffron is also an antioxidant. This means that, as an "anti-aging" agent, it neutralises free radicals. Specifically, methanol extractions of saffron neutralise at high rates the DPPH (IUPAC nomenclature: 1,1-diphenyl-2-picrylhydrazyl) radicals. This occurred via vigorous proton donation to DPPH by two of saffron's active agents, safranal and crocin. Thus, at concentrations of 500 and 1000 ppm crocin studies showed neutralisation of 50% and 65% of radicals, respectively. Safranal displayed a lesser rate of radical neutralisation than crocin, however. Such properties give saffron extracts promise as an ingredient for use as an antioxidant in pharmaceuticals, cosmetics, and as a food supplement. Ingested at high enough doses, however, saffron is lethal. Several studies done on lab animals have shown that saffron's LD50 (semilethal dose, or the dose at which 50% of test animals die from overdose) is 20.7 g/kg when delivered via a decoction.
 
Coloring and perfumery
Buddhist clergy, such as these monks in Thailand, often donned saffron-hued robes. Traditionally, these were colored using saffron-based dyes.
Despite its high cost, saffron has also been used as a fabric dye, particularly in China and India. Nevertheless, it is an unstable coloring agent; the initially vibrant orange-yellow that it imparts on clothes quickly fades to a pale and creamy yellow. The saffron stigmas, even when used in minute quantities, produce a luminous yellow-orange color. Increasing the amount of saffron applied will turn the fabric's imparted color an increasingly rich shade of red. Traditionally, the noble classes were the exclusive users of saffron-dyed clothes. Saffron was thus accorded a ritualized and caste-representative significance. Saffron dye also has been responsible for the saffron, vermilion, and ochre hues of the distinctive mantles and robes worn by Hindu and Buddhist monks. Meanwhile, in medieval Europe, well-to-do Irish and Highland Scots would wear a long linen undershirt known as a léine. According to John Major's 1521 History of Greater Britain, the léine was traditionally dyed with saffron.
There have been many attempts to substitute a cheaper dye for the costly saffron. But turmeric and most other spices similar to saffron do not produce such colors. They yield instead a bright yellowish hue. Nevertheless, saffron dye's main constituent, the flavonoid crocin, has been discovered in the gardenia fruit. Because gardenia is much less expensive to cultivate than saffron, it is currently being researched in China as a more economical source for saffron-like dyes.
 Saffron has also been used for its aromatic properties alone. In Europe, for instance, saffron threads were processed and combined with such ingredients as alkanet, dragon's blood (for color), and wine (for color) to produce an aromatic oil known then as crocinum. Crocinum was then applied as a perfume to hair. Another preparation involved the mixing of saffron with wine to produce a viscous yellow spray that was copiously applied to freshen the air of Roman theatres.

Modern trade
The vast majority of saffron is produced in a wide geographical belt extending from the Mediterranean in the west to Kashmir in the east. Small amounts are produced outside of this zone on all continents except Antarctica. Annually, some 300 tons of saffron spice, both the whole stigmas and in powdered form are produced worldwide. This is compared to the 50 tons of top-grade "coupe" saffron produced annually in 1991. Iran, Spain, India, Greece, Azerbaijan, Morocco, and Italy (in decreasing order of production) are the major producers of saffron. Iran and Spain alone are responsible for more than 80% of the world's saffron harvest.
The high cost of saffron is due to the difficulty of manually extracting large numbers of minutes stigmas; the only part of the crocus with the desired properties of aroma and flavor. In addition, a large number of flowers need to be processed in order to yield marketable amounts of saffron. A pound of dry saffron (0.45 kg) requires the harvesting of some 50,000 flowers, the equivalent of a football field's area of cultivation. By another estimate, some 75,000 flowers are needed to produce one pound of dry saffron. This too depends on the average size of each saffron cultivar's stigmas. Another complication arises in the flowers' simultaneous and transient blooming. Since some 150,000 crocus flowers are needed to produce just one kg of dry saffron, about forty hours of intense labor, harvesting is often a frenetic affair. In Kashmir, for example, the thousands of growers must work continuously in relays over the span of one or two weeks throughout both day and night.

Harvested saffron crocus flowers
After they are extracted, the stigmas must be dried quickly, lest decomposition or mold ruin the batch's marketability. The traditional method of drying involves spreading the fresh stigmas over screens of fine mesh, which are then baked over hot coals or wood or in oven-heated rooms with temperatures reaching 30-35 °C for 10–12 hours. Afterwards, the dried spice is preferably sealed in airtight glass containers. Bulk quantities of relatively lower-grade saffron can reach upwards of US$500/pound, while retail costs for small amounts may exceed 10 times that rate. In Western countries, the average retail price is approximately $1,000 per pound, however. The high price is somewhat offset by the small quantities needed: a few grams at most in medicinal use and a few strands per person in culinary applications; there are between 70,000 and 200,000 strands in a pound.
Experienced saffron buyers often have rules of thumb when deliberating on their purchases. They may look for threads exhibiting a vivid crimson coloring. They also reject threads that display the telltale dull brick red coloring that comes with age. They also seek a slight moistness and elasticity while looking for broken-off debris collected at the container's bottom. Such debris indicates the dryness of age has caused the saffron threads to break apart. Such traits of age are more likely to be encountered around the main June harvest season, when retailers try to clear out the previous season's old inventory to make room for the new crop. Indeed, experienced buyers recommend that only the current season's threads should be used at all. Thus, reputable saffron wholesalers and retailers will indicate the year of harvest or the two years that bracket the harvest date; a late 2002 harvest would be shown as "2002/2003".

Grading
Saffron types are graded by quality according to laboratory measurements of such characteristics as crocin (color), picrocrocin (taste), and safranal (fragrance) content. Other metrics include floral waste content (i.e. the saffron spice sample's non-stigma floral content) and measurements of other extraneous matter such as inorganic material ("ash"). A uniform set of international standards in saffron grading was established by the International Standards Organization, which is an international federation of national standards bodies. Namely, ISO 3632 deals exclusively with saffron. It establishes four empirical grades of color intensity: IV (poorest), III, II, and I (finest quality). Saffron samples are then assigned to one of these grades by gauging the spice's crocin content, which is revealed by measurements of crocin-specific spectroscopic absorbance. Absorbance is defined as Aλ = − log(I / I0), with Aλ as absorbance. It is a measure of a given substance's transparency (I / I0, the ratio of light intensity passing through sample to that of the incident light) to a given wavelength of light.
For saffron, absorbance is determined for the crocin-specific photon wavelength of 440 nm in a given dry sample of spice. Higher absorbances at this wavelength imply greater crocin concentration, and thus a greater colourative intensity. These data are measured through photospectroscopy reports at certified testing laboratories worldwide. These color grades proceed from grades with absorbance’s lower than 80 (for all category IV saffron) up to 190 or greater (for category I). The world's very finest samples (the selected most red-maroon tips of stigmas picked from the finest flowers) receive absorbance scores in excess of 250. Market prices for saffron types follow directly from these ISO scores. However, many growers, traders, and consumers reject such lab test numbers. They prefer a more holistic method of sampling batches of thread for taste, aroma, pliability, and other traits in a fashion similar to that practiced by practiced wine tasters.
Despite these attempts at quality control and standardization, a rich history of saffron adulteration continues into the present. Saffron adulteration was first documented in Europe's Middle Ages, when those found guilty of selling adulterated saffron were executed under the Safranschou code. Traditional methods include mixing in extraneous substances; examples included beet, pomegranate fibers, red-dyed silk fibers, or the saffron crocus's tasteless and odorless yellow stamens, with the saffron threads or powder in order to increase its mass. Fraudulent practices also included the dousing of genuine saffron fibers with viscid substances such as honey or vegetable oil. Powdered saffron is far more susceptible to adulteration, however. Turmeric, paprika, and other substances were and still are often combined with saffron powder. Cheaper grades and samples of saffron are more likely to be adulterated. In addition, adulteration can arise from the illegal mixing of relatively inexpensive (lower) saffron grades with premium categories. Thus, in India, rich and premium Kashmiri saffron is often sold mixed with cheaper and lower quality Iranian imports. These mixes are then marketed as pure Kashmiri saffron, a development that has cost Kashmiri growers much of their income.