Saffron

Saffron (pronounced /ˈsæfrən/, /ˈsæfrɒn/) is a spice derived from the flower of the saffron crocus (Crocus sativus), a species of crocus in the family Iridaceae. The flower has three stigmas, which are the distal ends of the plant's carpels. Together with its style, the stalk connecting the stigmas to the rest of the plant, these components are often dried and used in cooking as a seasoning and colouring agent. Saffron, which has for decades been the world's most expensive spice by weight,^[1][2] is native to Southwest Asia.^[2][3] It was first cultivated in the vicinity of Greece.^[4]

Saffron is characterised by a bitter taste and an iodoform- or hay-like fragrance; these are caused by the chemicals picrocrocin and safranal.^[5][6] It also contains a carotenoid dye, crocin, that gives food a rich golden-yellow hue. These traits make saffron a much-sought 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.^[7] Safranum comes from the Arabic word aṣfar (أَصْفَر‎), which means "yellow," via the paronymous zaʻfarān (زَعْفَرَان‎), the name of the spice in Arabic.^[6][8]

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Biology

The domesticated saffron crocus C. sativus is an autumn-flowering perennial plant unknown in the wild, and is a sterile triploid mutant of the eastern Mediterranean autumn-flowering Crocus cartwrightianus.^[9] According to botanical research, C. cartwrightianus originated in Crete, not—as was once generally believed—in Central Asia.^[6] The saffron crocus resulted when C. cartwrightianus was subjected to extensive artificial selection by growers who desired elongated stigmas. Being sterile, the saffron crocus's purple flowers fail to produce viable seeds—thus, reproduction is 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, reproducing via division into up to ten "cormlets" that eventually give rise to new plants.^[9] The corms are small brown globules up to 4.5 centimetres (1.8 in) in diameter and are shrouded in a dense mat of parallel fibers.

After a period of aestivation in summer, five to eleven narrow and nearly vertical green leaves—growing up to 40 cm (16 in) in length—emerge from the ground. In autumn, purple buds appear. Only in October, after most other flowering plants have released their seeds, does it develop its brilliantly hued flowers, ranging from a light pastel shade of lilac to a darker and more striated mauve.^[10] Upon flowering, it averages less than 30 cm (12 in) in height.^[11] Inside each flower is a three-pronged style; in turn, each prong terminates with a crimson stigma 25–30 mm in length.^[9]

Cultivation

  The saffron crocus thrives in climates similar to that of the Mediterranean maquis or the North American chaparral, where hot, dry summer breezes blow across arid and semi-arid lands. Nevertheless, the plant can tolerate cold winters, surviving frosts as cold as −10 °C (14 °F) and short periods of snow cover.^[12][9] However, if not grown in wet environments like Kashmir (where rainfall averages 1000–1500 mm annually), irrigation is needed—this is true in the saffron-growing regions of Greece (500 mm of rainfall annually) and Spain (400 mm). Rainfall timing is also key: generous spring rains followed by relatively dry summers are optimal. In addition, rainfall occurring immediately prior to flowering also boosts saffron yields; nevertheless, rainy or cold weather occurring during flowering promotes disease, thereby reducing yields. Persistently damp and hot conditions also harm yields,^[13] as do the digging actions of rabbits, rats, and birds. Parasites such as nematodes, leaf rusts, and corm rot also pose significant threats.^[14]

Saffron plants grow best in strong and direct sunlight, and fare poorly in shady conditions. Thus, planting is best done in fields that slope towards the sunlight (i.e. south-sloping in the Northern Hemisphere), maximizing the crocuses' sun exposure. In the Northern Hemisphere, planting is mostly done in June, with corms planted some 7–15 cm deep. Planting depth and corm spacing—along with climate—are both critical factors impacting plant yields. Thus, mother corms planted more deeply yield higher-quality saffron, although they produce fewer flower buds and daughter corms. With such knowledge, Italian growers have found that planting corms 15 centimetres (5.9 in) deep and in rows spaced 2–3 cm apart optimizes threads yields, whereas planting depths of 8–10 cm optimizes flower and corm production. Meanwhile, Greek, Moroccan, and Spanish growers have devised different depths and spacings to suit their own climates.^[13]

Saffron 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, soil organic content was boosted via application of some 20–30 tonnes of manure per hectare. Afterwards—and with no further manure application—corms were planted.^[14] 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 the plants begin to flower. Harvesting of flowers is by necessity a speedy affair: after their flowering at dawn, flowers quickly wilt as the day passes.^[15] Furthermore, saffron crocuses bloom within a narrow window spanning one or two weeks.^[16] Approximately 150 flowers yield 1 g of dry saffron threads; to produce 12 g of dried saffron (72 g freshly harvested), 1 kg of flowers are needed (1 lb for 0.2 oz of dried saffron). On average, one freshly picked flower yields 0.03 g of fresh saffron, or 0.007 g of dried saffron.^[14]

Chemistry

Saffron contains more than 150 volatile and aroma-yielding compounds. It also has many nonvolatile active components,^[18] many of which are carotenoids, including zeaxanthin, lycopene, and various α- and β-carotenes. However, saffron's golden yellow-orange colour is primarily the result of α-crocin. This crocin is trans-crocetin di-(β-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.^[18] Crocins themselves are a series of hydrophilic carotenoids that are either monoglycosyl or diglycosyl polyene esters of crocetin.^[18] 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.^[4]

The bitter glucoside picrocrocin is responsible for saffron's flavour. 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-coloured^[19] 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.^[17] Safranal, a volatile oil, gives saffron much of its distinctive aroma.^[5][20] Safranal is less bitter than picrocrocin and may comprise up to 70% of dry saffron's volatile fraction in some samples.^[19] 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".^[21] Chemists found this to be the most powerful contributor to saffron's fragrance despite its being present in a lesser quantity than safranal.^[21] 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 minimise contact with atmospheric oxygen. Saffron is somewhat more resistant to heat.

History

Main article: History of saffron

The history of saffron cultivation reaches back more than 3,000 years.^[9] 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.^[22] 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.^[23] 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.

Mediterranean

Minoans portrayed saffron in their palace frescoes by 1500–1600 BC, showing saffron's use as a therapeutic drug.^[24][23] Later, Greek legends told of sea voyages to Cilicia. There, adventurers hoped to procure what they believed was the world's most valuable saffron.^[12] Another legend tells of Crocus and Smilax, whereby Crocus is bewitched and transformed into the original saffron crocus.^[25] Ancient Mediterranean peoples—including perfumers in Egypt, physicians in Gaza, townspeople in Rhodes,^[26] and the Greek hetaerae courtesans—used saffron in their perfumes, ointments,^[27] potpourris, mascaras, divine offerings, and medical treatments.^[27]  

In late Hellenistic Egypt, Cleopatra used saffron in her baths so that lovemaking would be more pleasurable.^[28] Egyptian healers used saffron as a treatment for all varieties of gastrointestinal ailments.^[29] Saffron was also used as a fabric dye in such Levant cities as Sidon and Tyre.^[30] Aulus Cornelius Celsus prescribes saffron in medicines for wounds, cough, colic, and scabies, and in the mithridatium.^[31] 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 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.^[32]

Asia

Saffron-based pigments have been found in 50,000 year-old depictions of prehistoric beasts in what is today Iraq.^[25][33] Later, the Sumerians used wild-growing saffron in their remedies and magical potions.^[34] 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.^[35] Ancient Persians cultivated Persian saffron (Crocus sativus 'Hausknechtii') in Derbena, Isfahan, and Khorasan by the 10th century BC. At such sites, saffron threads were woven into textiles,^[25] ritually offered to divinities, and used in dyes, perfumes, medicines, and body washes.^[36] 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.^[27] During his Asian campaigns, Alexander the Great used Persian saffron in his infusions, rice, and baths as a curative for battle wounds. Alexander's troops mimicked the practice and brought saffron-bathing back to Greece.^[37]

Theories explaining saffron's arrival in South Asia conflict. Traditional Kashmiri and Chinese accounts date its arrival anywhere between 900–2500 years ago.^[38][39] Meanwhile, historians studying ancient Persian records date the arrival to sometime prior to 500 BC,^[4] attributing it to either Persian transplantation of saffron corms to stock new gardens and parks^[40] or to a Persian invasion and colonization of Kashmir. Phoenicians then marketed Kashmiri saffron as a dye and a treatment for melancholy.^[27] From there, saffron use in foods and dyes spread throughout South Asia. For example, Buddhist monks in India adopted saffron-coloured robes after the Buddha Siddhartha Gautama's death.^[41]

Some historians believe that saffron first came to China with Mongol invaders by way of Persia.^[42] On the other hand, saffron is mentioned in ancient Chinese medical texts, including the forty-volume Shennong Bencaojing (神農本草經—"Shennong's Great Herbal", also known as Pen Ts'ao or Pun Tsao) pharmacopoeia, a tome dating from 200–300 BC. Traditionally attributed to the legendary Yan ("Fire") Emperor (炎帝) Shennong, it documents 252 phytochemical-based medical treatments for various disorders.^[43][44][41] 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 "[t]he 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 colour. It can be used to aromatise wine."

Europe

In Europe, saffron cultivation declined steeply following the Roman Empire's fall. Saffron was reintroduced when Moorish civilization spread to Spain, France, and Italy.^[45] 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^[46] such as Rhodes. The theft of one such shipment by noblemen sparked the fourteen-week long "Saffron War".^[46] The conflict and resulting fear of rampant saffron piracy spurred significant saffron cultivation in Basel, which grew prosperous.^[47] Cultivation and trade then spread to Nuremberg, where epidemic levels of saffron adulteration brought on the Safranschou code, under which saffron adulterers were fined, imprisoned, and executed.^[48] 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 such as chocolate, coffee, tea, and vanilla from newly contacted Eastern and overseas countries caused European cultivation and usage of saffron to decline.^[49][50] Only in southern France, Italy, and Spain, did significant cultivation endure.^[51]

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.^[52] By 1730, the Pennsylvania Dutch were 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.^[53] The trade with the Caribbean later collapsed in the aftermath of the War of 1812, when many saffron-transporting merchant vessels were destroyed.^[54] 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.^[55] American saffron cultivation survived into modern times mainly in Lancaster County, Pennsylvania.^[52]

Trade and use

Main article: Trade and use of saffron

Saffron's aroma is often described by connoisseurs as reminiscent of metallic honey with grassy or hay-like notes, while its taste has also been noted as hay-like and somewhat bitter. Saffron also contributes a luminous yellow-orange colouring to foods. Saffron is widely used in Persian, Arab, Central Asian, European, Indian, Iranian, Moroccan and Cornish cuisines. Confectionaries and liquors also often include saffron. Common saffron substitutes include safflower (Carthamus tinctorius, which is often sold as "Portuguese saffron" or "assafroa") and turmeric (Curcuma longa). Medicinally, saffron has a long history as part of traditional healing; modern medicine has also discovered saffron as having anticarcinogenic (cancer-suppressing),^[18] anti-mutagenic (mutation-preventing), immunomodulating, and antioxidant-like properties.^[56][18][57] Saffron has also been used as a fabric dye, particularly in China and India, and in perfumery.

Most saffron is grown in a belt of land ranging from the Mediterranean in the west to Kashmir in the east. Annually, around 300 tonnes of saffron are produced worldwide.^[6] Iran, Spain, India, Greece, Azerbaijan, Morocco, and Italy (in decreasing order of production) are the major producers of saffron. A pound of dry saffron (0.45 kg) requires 50,000–75,000 flowers, the equivalent of a football field's area of cultivation.^[58][59] Some forty hours of frenetic day-and-night labour are needed to pick 150,000 flowers.^[60] Upon extraction, stigmas are dried quickly and (preferably) sealed in airtight containers.^[61] Saffron prices at wholesale and retail rates range from US$500/pound to US$5,000/pound (US$1100–US$11,000 per kilogram)—equivalent to £2,500/€3,500 per pound or £5,500/€7,500 per kilo. In Western countries, the average retail price is $1,000/£500/€700 per pound (US$2200/£1100/€1550 per kilogram).^[2] A pound comprises between 70,000 and 200,000 threads. Vivid crimson colouring, slight moistness, elasticity, recent harvest date, and lack of broken-off thread debris are all traits of fresh saffron.

Cultivars

Several saffron cultivars are grown worldwide. Spain's varieties, including the tradenames 'Spanish Superior' and 'Creme', are generally mellower in colour, flavour, and aroma; they are graded by government-imposed standards. Italian varieties are more potent, while the most intense varieties tend to be Macedonian Greek, Iranian, and Indian in origin. Westerners may face significant obstacles in obtaining saffron from India. For example, India has banned the export of high-grade saffron abroad. Aside from these, various "boutique" crops are available from New Zealand, France, Switzerland, England, the United States, and other countries, some organically grown. In the U.S., Pennsylvania Dutch saffron—known for its earthy notes—is marketed in small quantities.^[52][62]

Consumers regard certain cultivars as "premium" quality. The "Aquila" saffron (zafferano dell'Aquila)—defined by high safranal and crocin content, shape, unusually pungent aroma, and intense colour—is grown exclusively on eight hectares in the Navelli Valley of Italy's Abruzzo region, near L'Aquila. It was first introduced to Italy by a Dominican monk from Inquisition-era Spain. But in Italy the biggest saffron cultivation, for quality and quantity, is in San Gavino Monreale, Sardinia. There, saffron is grown on 40 hectares (60% of Italian production); it also has very high crocin, picrocrocin, and safranal content. Another is the Kashmiri "Mongra" or "Lacha" saffron (Crocus sativus 'Cashmirianus'), which is among the most difficult for consumers to obtain. Repeated droughts, blights, and crop failures in Kashmir, combined with an Indian export ban, contribute to its high prices. Kashmiri saffron is recognisable by its extremely dark maroon-purple hue, among the world's darkest, which suggests the saffron's strong flavour, aroma, and colourative effect.

Grades

Saffron types are graded by quality according to laboratory measurements of such characteristics as crocin (colour), 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 Organization for Standardization, which is an international federation of national standards bodies. Namely, ISO 3632 deals exclusively with saffron. It establishes four empirical grades of colour 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 A_λ = − log(I / I₀), with A_λ as absorbance (Beer-Lambert law). 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.^[63] Higher absorbances at this wavelength imply greater crocin concentration, and thus a greater colourative intensity. These data are measured through spectrophotometry reports at certified testing laboratories worldwide. These colour grades proceed from grades with absorbances lower than 80 (for all category IV saffron) up to 190 or greater (for category I). The world's 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.^[63] 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 practised wine tasters.^[64]

Despite such attempts at quality control and standardisation, an extensive history of saffron adulteration—particularly among the cheapest grades—continues into modern times. Adulteration was first documented in Europe's Middle Ages, when those found selling adulterated saffron were executed under the Safranschou code.^[65] Typical methods include mixing in extraneous substances like beet, pomegranate fibers, red-dyed silk fibers, or the saffron crocus's tasteless and odorless yellow stamens. Other methods included dousing saffron fibers with viscid substances like honey or vegetable oil. However, powdered saffron is more prone to adulteration, with turmeric, paprika, and other powders used as diluting fillers. Adulteration can also consist of selling mislabeled mixes of different saffron grades.^[41] Thus, in India, high-grade Kashmiri saffron is often sold mixed with cheaper Iranian imports; these mixes are then marketed as pure Kashmiri saffron, a development that has cost Kashmiri growers much of their income.^[66][67]

Notes

References