Saffron ( ; ) is a spice derived from the sterile autumn-blooming flower of Crocus sativus, commonly known as the "saffron crocus". The vivid crimson stigma and styles (in industry jargon: 'threads') are collected and dried for use mainly as a food seasoning and colourant. Saffron crocus was slowly propagated throughout much of Eurasia and later brought to parts of North Africa, North America, even as far as Fiji in Oceania by its Indian migrant descendant population.
Saffron's taste and iodoformic or hay-like fragrance result from the phytochemicals picrocrocin and safranal. It also contains a carotenoid pigment, crocin, which imparts a rich golden-yellow hue to dishes and textiles. Saffron quality is objectively measured under the ISO 3632 standard, which evaluates the concentration of active phytochemicals—specifically crocin (color), picrocrocin (taste), and safranal (aroma) via spectrophotometric laboratory analysis. The grading depends largely on the ratio of dark red stigmas to yellow styles, with higher concentrations of red parts yielding premium-grade products. Although market prices fluctuate, premium saffron regularly exceeds US$5,000 per kilogram, sustained by its labor-intensive hand-harvesting process.
Saffron originated in Iran especially in the Khorasan region descended from wild relatives in the eastern Mediterranean and later spread to Kashmir, the Mediterranean region, and Asia Minor. It has been cultivated in sunny, temperate climates and traded for over 3,500 years across Eurasia, spreading through Asia via cultural exchange and conquest. Its recorded history is attested as early as a 7th-century BC Assyrian botanical treatise. Saffron is an essential ingredient in Persian cuisine used in dishes such as chelow and tahdig, stews like khoresh-e fesenjan, and desserts including sholeh-zard and bastani sonnati. Additional historical uses include traditional medicine, dyeing, perfumery, and religious rituals.
Etymology
The English word saffron is a borrowing from French, first found in a Middle English text written around 1200 as . It derives from the 12th-century Old French term , which comes from the Medieval Latin word , and from the Persian . It originated from the older , meaning 'gold-strung' in reference to the flower's golden filaments or the rich golden hue it imparts as a spice.
Species
Description
The domesticated saffron crocus, Crocus sativus, is an autumn-flowering perennial plant unknown in the wild. It possibly descends from the eastern Mediterranean autumn-flowering Crocus cartwrightianus which is also known as "wild saffron" and is native to mainland Greece, Euboea, Crete, Skyros and some islands of the Cyclades. The similar species C. thomasii and C. pallasii were considered as other possible ancestors. As a genetically monomorphic clone incapable of seed production, it was slowly propagated by humans throughout much of Eurasia. Various origins have been suggested for saffron, including Iran, Mesopotamia, Kashmir and Greece.
It is a sterile triploid form, which means that three homologous sets of chromosomes make up each specimen's genetic complement; C. sativus bears eight chromosomal bodies per set, making for 24 in total. Being sterile, the purple flowers of C. sativus fail to produce viable seeds; reproduction hinges on human assistance: clusters of corms, underground, bulb-like, starch-storing organs, must be dug up, divided, and replanted. A corm survives for one season, producing via vegetative division up to ten "cormlets" that can grow into new plants in the next season. The compact corms are small, brown globules that can measure as large as in diameter, have a flat base, and are shrouded in a dense mat of parallel fibres; this coat is referred to as the "corm tunic". Corms also bear vertical fibres, thin and net-like, that grow up to above the plant's neck.
The plant sprouts 5–11 white and non-photosynthetic leaves known as cataphylls. These membrane-like structures cover and protect 5 to 11 true leaves as they bud and develop on the crocus flower. The latter are thin, straight, and blade-like green foliage leaves, which are , in diameter, which either expand after the flowers have opened ("hysteranthous") or do so simultaneously with their blooming ("synanthous"). C. sativus cataphylls are suspected by some to manifest prior to blooming when the plant is irrigated relatively early in the growing season. Its floral axes, or flower-bearing structures, bear bracteoles, or specialised leaves, that sprout from the flower stems; the latter are known as pedicels. After aestivating in spring, the plant sends up its true leaves, each up to in length. Only in October, after most other flowering plants have released their seeds, do its brilliantly hued flowers develop; they range from a light pastel shade of lilac to a darker and more striated mauve. The flowers possess a sweet, honey-like fragrance. Upon flowering, the plants are in height and bear up to four flowers. A three-pronged style in length, emerges from each flower. Each prong terminates with a vivid crimson stigma, which is the distal end of a carpel.
Cultivation The saffron crocus, unknown in the wild, probably descends from Crocus cartwrightianus. It is a triploid that is "self-incompatible" and male sterile; it undergoes aberrant meiosis and is hence incapable of independent sexual reproduction—all propagation is by vegetative multiplication via manual "divide-and-set" of a starter clone or by interspecific hybridisation.
Crocus sativus thrives in the Mediterranean maquis, an ecotype superficially resembling the North American chaparral, and similar climates where hot and dry summer breezes sweep semi-arid lands. It can nonetheless survive cold winters, tolerating frosts as low as and short periods of snow cover. Some reports suggest saffron can tolerate an air temperature range from −22 to 40 °C. Irrigation is required if grown outside of moist environments such as Kashmir, where annual rainfall averages ; saffron-growing regions in Greece ( annually) and Spain () are far drier than the main cultivating Iranian regions. What makes this possible is the timing of the local wet seasons; generous spring rains and drier summers are optimal. Rain immediately preceding flowering boosts saffron yields; rainy or cold weather during flowering promotes disease and reduces yields. Persistently damp and hot conditions harm the crops, and rabbits, rats, and birds cause damage by digging up corms. Nematodes, leaf rusts, and corm rot pose other threats. Yet Bacillus subtilis inoculation may provide some benefit to growers by speeding corm growth and increasing stigma biomass yield.
The plants fare poorly in shady conditions; they grow best in full sunlight. Fields that slope towards the sunlight are optimal (i.e., south-sloping in the Northern Hemisphere). Planting is mostly done in June in the Northern Hemisphere, where corms are lodged deep; its roots, stems, and leaves can develop between October and February. Planting depth and corm spacing, in concert with climate, are critical factors in determining yields. Mother corms planted deeper yield higher-quality saffron, though they form fewer flower buds and daughter corms. Italian growers optimise thread yield by planting deep and in rows apart; depths of optimise flower and corm production. Greek, Moroccan, and Spanish growers employ distinct depths and spacings that suit their locales.
C. sativus prefers friable, loose, low-density, well-watered, and well-drained clay-calcareous soils with high organic content. Traditional raised beds promote good drainage. Soil organic content was historically boosted via application of some of manure. Afterwards, and with no further manure application, corms were planted. After a period of dormancy through the summer, the corms send up their narrow leaves and begin to bud in early autumn. Only in mid-autumn do they flower. Harvests are by necessity a speedy affair: after blossoming at dawn, flowers quickly wilt as the day passes. All plants bloom within a window of one or two weeks. Stigmas are dried quickly upon extraction and (preferably) sealed in airtight containers.
Harvesting
The high retail value of saffron is maintained on world markets because of labour-intensive harvesting methods, which require some – equivalently, . Forty hours of labour are needed to pick 150,000 flowers.
One freshly picked crocus flower yields on average 30 mg of fresh saffron or 7 mg dried; roughly 150 flowers yield of dry saffron threads; to produce of dried saffron, of flowers are needed; the yield of dried spice from fresh saffron is only .
Spice
Phytochemistry and sensory properties
Saffron contains some 28 volatile and aroma-yielding compounds, dominated by ketones and aldehydes. Its main aroma-active compounds are safranal – the main compound responsible for saffron aroma – 4-ketoisophorone, and dihydrooxophorone. Saffron also contains nonvolatile phytochemicals, including the carotenoids zeaxanthin, lycopene, various α- and β-carotenes, as well as crocetin and its glycoside crocein, which are the most biologically active components. Because crocetin is smaller and more water-soluble than the other carotenoids, it is more rapidly absorbed.
The yellow-orange colour of saffron is primarily the result of α-crocin. This crocin is trans-crocetin di-(β-D-gentiobiosyl) ester; it bears the 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. 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 make up more than 10% of dry saffron's mass. The two esterified gentiobioses make α-crocin ideal for colouring water-based and non-fatty foods such as rice dishes.
The bitter glucoside picrocrocin is responsible for saffron's pungent flavour. Picrocrocin (chemical formula: ; systematic name: 4-(β-D-glucopyranosyloxy)-2,6,6-trimethylcyclohex-1-ene-1-carbaldehyde) is a union of an aldehyde sub-molecule known as safranal (systematic name: 2,6,6-trimethylcyclohexa-1,3-diene-1-carbaldehyde) and a carbohydrate. It has insecticidal and pesticidal properties, and may comprise up to 4% of dry saffron. Picrocrocin is a truncated version of the carotenoid zeaxanthin that is produced via oxidative cleavage, and is the glycoside of the terpene aldehyde safranal.
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 molecule underlying saffron's aroma is 2-hydroxy-4,4,6-trimethyl-2,5-cyclohexadien-1-one, which produces a scent described as saffron, dried hay-like. Chemists find this is the most powerful contributor to saffron's fragrance, despite its presence in a lesser quantity than safranal. Dry saffron is highly sensitive to fluctuating pH levels, and rapidly breaks down chemically in the presence of light and oxidising agents. It must, therefore, be stored in air-tight containers to minimise contact with atmospheric oxygen. Saffron is somewhat more resistant to heat.
Grades and ISO 3632 categories
Saffron is not all of the same quality and strength. Strength is related to several factors, including age and the amount of yellow style picked relative to red stigma, as colour and flavour are concentrated in the latter.