Saffron - Production and uses

Saffron

1 Introduction

Saffron, the most expensive spice in the world, is derived from the dry stigmata of the saffron crocus Crocus sativus L., a member of the family Iridaceae. The plant is a sterile autotriploid cultigen, 2n = 24, possibly selected from C. cartwrightianum Herbet, of Greek origin. The family Iridaceae is included in the order Liliales, subclass Liliidae

(Monocots), and is divided into four subfamilies; Crocus L. belongs to subfamily Ixioideae tribe Ixieae.¹ C. sativus is a plant of 1030 cm and has a corm-tunic finely fibrous; the fibres reticulate. It has 610 leaves present at anthesis, 12 flowers of a lilac- purple colour, with perianth segments of 3.55 cm and style branches of 2.53.2 cm. The yellow style is deeply divided into three branches, and the stigmata are bright red. The flowering season is from October to December.²

The first mention of the crop of saffron dates back to 2300 BC. Sargon, founder of the Accadian empire, was born at an unknown village, the City of Saffron, Azupirano, near the river Euphrates in Babylon. The Harvester of saffron appears in the Minoan pottery and frescoes (17001600 BC) of the Palace of Minos in Knossos (Crete). Another fresco dated about 1500 BC is at Akrotini on the Island of Thera (Santorini). Krokos was the Greek word for saffron and appears in the songs IX and XII of the Iliad by Homer. In Greek mythology, Krokos, the lover of nymph Esmilax, was transformed into the plant saffron by Hermes. Saffron was also known in ancient Egypt and mentioned in the Ebers papyrus. In the Bible, saffron was karkon (in Hebrew) and is referred to in the Song of the Songs (4:14) of King Solomon X or IX century BC. There is evidence of its medicinal use in Kashmir in 500 BC.³

The word saffron is derived from the arabic word Za.feraan and the Arabs are sometimes credited with the introduction of saffron in Spain around the tenth century.

2 Chemical structure

In ancient times saffron was an important dye, but nowadays its main uses are cooking and colouring foods, especially Spanish rice (paella), bouillabaisse and in Cornwall,

traditional saffron cakes and loaves. The major components responsible for the colouring strength of saffron are cis and trans crocins. Crocins are unusual water-soluble carotenoids. With concentrated sulphuric acid their red colour changes to blue

(polychroit). The molecular formula of the most common crocin (a digentiobiosyl ester of crocetin) is C₄₄H₆₄O This crocin is a bis-(6-O- -D-glucopyranosyl- -D- glucopyranoside) ester of crocetin (= di-( -gentiobiosyl)-crocetin), C₂₀H₂₄O₄ a carotenoid 8,8 -diapo- , -carotendioic acid (trans-crocetin). In addition to crocin there are some more esters (all-trans and 13-cis isomers) of crocetin in saffron (Fig.

1). Crocins are produced in the plant kingdom from a glucoside derivative of zeaxanthin (all-trans- -carotene-3,3 -diol, C₄₀H₅₆O₂) named protocrocin, which by enzymatic oxidative degradation (Fig. 2) produces one molecule of crocin and two molecules of picrocrocin, the substance responsible for saffrons bitter taste. Crocins have also been found in the fruits of Gardenia jasminoides Ellis (Rubiaceae), in Nycthanthus arbor-tristis L. (Oleaceae) from India, in Crocus albiflorus Kit var. neapolitanus Hort., and in C. lutens Lam.⁴⁶

Fig. 1 The crocins. All-trans-crocins and 13-cis-isomers.

(Adapted from Tarantilis P A et al., J Chromatography, 1995 699 10718.)

Fig. 2 Biosynthesis of crocin, picrocrocin and safranal.

Fig. 3 Characteristic cyclohexane derivatives of saffrons aroma.

(Adapted from Tarantilis et al., J Agric Food Chem, 1997 45 45962.)

Picrocrocin or saffron bitter C₁₆H₂₆O₇ (R-4-( -D-glucopyranoxyloxy)-2,6,6-trimethyl-

1-cyclohexene-1-carboxaldehyde), is responsible for the bitter taste of the spice. By submitting picrocrocin to hydrolysis and dehydration, safranal, the principal substance responsible for the aroma of saffron, is obtained. Safranal (C₁₀H₁₄O) corresponds to

2,6,6-trimethyl-1,3-cyclohexadiene-1-carboxaldehyde (= -dehydrocyclocitral). By enzymatic hydrolysis of picrocrocin with a -glucosidase, 4-OH- -cyclocitral is produced and this component gives safranal by dehydration. The essential oil obtained by hydrodistillation of saffron contains safranal as main constituent and many other derivatives of cyclohexane (Fig. 3). In addition to crocin, safranal and picrocrocin, Spanish saffron with a water content of 15.6% contains protein (1014%), sugars (13

14%), starch (67%), gums and dextrin (910%), pentoses (67%), ash (58%), fibre (4

5%), volatile oil (0.8%), fatty oil (813%) with glycerin esters of palmitic, stearic, lauric, and oleic acids; 56138 /g vitamin B₂, 0.74.0 /g vitamin B₁ xanthophylls, carotenes

( , and ), lycopine and zeaxanthin; Ca (111 mg), Fe (11.1 mg), P (252 mg), Na

(148 mg), K (1724 mg). Saffron is the richest known source of vitamin B₂.⁴⁷

Picrocrocin and crocin are easily oxidized by direct contact with oxygen in the air. As saffron is used chiefly as a food additive for flavouring and colouring, the process of autooxidation is undesirable. Samples of saffron stored at 0sC and 17sC and 0% relative moisture showed no change in crocin and picrocrocin content. Therefore, low moisture content and low temperature are the best storage conditions. The colouring strength and bitter taste of dehydrated saffron are five times more concentrated than those of fresh saffron.^{8, 9}

3 Production

At present, the major saffron cultivating countries for trade are Spain, Iran, Greece, India, China and Morocco. Minor producers are Italy, Switzerland, France, Argentina and Azerbaijan. The spice is also produced in the southern hemisphere in New Zealand.¹⁰ In Spain the crop of saffron is of considerable importance, and it is mainly grown in the provinces of Albacete, Ciudad Real, Cuenca and Toledo (La Mancha region, southeastern Spain) and also in Teruel. One of the best quality saffrons are those harvested in La Mancha, traditionally regarded as Saffron Mancha or Azafran Mancha. Saffron in Spain is harvested and processed according to the following process.¹¹

The corms are planted in furrows. There are two rows of corms in each furrow and the depth of the furrow is 1215 cm. The distance between furrows is 2530 cm. The space between corms in a row is 10 cm and the distance between rows in each furrow is

810 cm. The planting season is from July to September. Large amounts of organic manure are incorporated into the soil before planting the corms. The artificial fertilizers used are a mixture of potassium sulphate and ammonium nitrate. In Spain, saffron is grown in dry temperature conditions (dry farming), but irrigation in March, April and August is frequent. In Spain the major pest is the common vole (a field mouse). Farmers usually fumigate their burrows or use traps to solve the problem. In other countries, rabbits are also a major pest problem. Rabbit-proof fencing may be required in areas where these pests are found. Saffron can suffer from a range of diseases, especially several fungi such as Rhizoctocnia and Sclerotinia (Phoma). Dipping corms in fungicide before planting, and using raised beds to improve drainage help minimize these problems. No herbicides have been tested for weed control in actively growing saffron.

Saffron is hand-harvested at the flowering season (still the only method for harvesting the crop) at the end of October and beginning of November. The process of picking the stigmata is done on the same day as harvesting. Once the stigmata have been separated from the flowers, careful drying is needed to produce a product of good quality. In Spain the traditional method involves gently toasting the stigmata in a silk sieve over the embers of a charcoal fire. The loss of weight in this process is about 80% with respect to fresh weight of stigmata. The final product may be stored in paper, cloth or plastic containers. In other countries, Iran for example, saffron is prepared by removing the whole style with the stigmata binding them together in bunches and sun drying. In New Zealand, saffron is dried in an airflow oven at 30sC for 34 hours.^{10, 11}

Most commercial production of saffron occurs in Spain and Iran. Saffron is grown successfully under rain-feed conditions in Kashmir (India), with an annual rainfall of

10001500 mm. Spring rain is favourable for corm production while rain immediately before flowering encourages high flower yield. Average yields of saffron in Spain and other commercial values, can be seen in Table 1.¹² In Kashmir the yield amounts to only 1.53.0 kg/ha (average). Between 70 000 and 200 000 flowers are needed to produce

1 kg of dried saffron threads. In New Zealand the rate is 165 000151 000 flowers/kg of dried saffron.^{10, 11} In India, the total production of saffron rose from 5 t in 1974 to 10 t in

1983. Iran is another major producer, growing 50 t of spice in 1989. Iran uses 1015 t in its domestic market and the rest is exported to Spain. Spain re-exports this product together with its own. Overall Spanish production is in decline mainly due to increasing labour costs and the unwillingness of young people to enter the industry. It is worth remembering that if one stigma of saffron weighs about 2 mg and each flower has three stigmata, 150 000 flowers must be carefully picked by hand one by one to obtain one kg of spice. The price on the international market is ca US$1000/kg. Retail prices, naturally, are much higher. For instance, the price of an envelope of 250 mg saffron in Spain is 260 pesetas, equivalent to 1 040 000 pesetas/kg (1015 US$/1 g).¹⁰¹²

Table 1 Commercial values of Spanish toasted saffron

Year Area Yield Production Field price Price (euro) Import Export

(ha) (kg/ha) (kg) (euro)/ Millions (tm) (tm)

kg of euros

1985 4,233 6.18 26,145 417 11.023 34

1986 4,067 8.74 35,537 422 15.067 34

1987 4,209 8.21 34,556 532 18.181 1

1988 4,229 4.82 20,374 662 13,487 2

1989 4,193 6.12 25,671 701 18,000 9 44

1990 3,696 5.89 21,789 613 13.348 7 31

1991 3,298 7.17 23,654 530 12.543 11 35

1992 2,582 5.23 13,500 493 6.647 12 207

1993 1,878 7.80 14,642 466 6.815 26 212

1994 1,406 6.71 9,431 491 4.628 23 64

1995 1,163 5.47 6,365 563 3.582 28 46

1996 1,020 5.43 5,541 605 3.348

Tm = metric ton; 1 euro = 166. 386 pesetas; ha = hectare

Source: Anuario de Estadıstica Agraria, MAPA, Servicio de Estadısticas Agrarias, Madrid (Spain), 1997. Adapted into English.

4 Uses

In modern times saffron is used almost exclusively as a culinary seasoning and to colour foods. The range of foods that have been spiced with saffron is wide, including cream or cottage cheese, bouillabaise, chicken and meat, rice, mayonnaise, liquors and cordials. Spanish, Italian and French cuisine favours the use of saffron. An example is rice

(Spanish paella and Zarzuela de pescado) in the Spanish cuisine or Rissotto a` la Milanesa an excellent Italian dish. It is often used in chicken and fish dishes. When using saffron threads, the recipe preparation must start steeping the stigmata to extract their essence for a minimum of 20 minutes in addition to cooking/baking time. This can be done in alcohol, an acidic liquid or hot liquid.^{3, 13, 14}

However, saffron has found its way into the cuisine of many European and Asian countries, especially in festive fare. Special Christmas bread and buns using saffron are traditional in Sweden. Saffron cakes are another speciality in parts of England. It is an essential commodity in high-quality, milk/cream-based confectioneries and Mughlai dishes in India wherein it imparts a rich colour and distinctive flavour. The average use of this spice in weddings in even a middle-class Indian family in the states of Rajasthan and Gujarat is about 250 g. In the western world, although its major use is as a spice, it is also employed as a health tonic without side effects. About 50 mg of saffron dissolved in a

200 ml glass of milk and a spoonful of sugar makes a very tasty drink which is also a health tonic. In Arab countries visitors are welcomed with a drink prepared from coffee, saffron and cardamom. In Japan it is employed to enhance the taste of fish and give it a golden-yellow colour.^{13, 14} In the food industry it is one of the ingredients in dehydrated foodstuff mixes, soups, ice cream and many other processed food products. Is also used, mainly in India, as a key ingredient in flavoured chewing tobacco as saffron enhances its taste to a great extent.^{13, 14}

Water-soluble crocins are the main pigments responsible for the colouring strength of the spice. In the ancient world, pigments used as dyes and colouring matters were rare and very expensive and were considered as status symbols often reserved for royalty. The saffron mantle of the Kings of Ireland and saffron-dyed material supplied by the Phoenicians to the Kings of Assyria are good examples. In order to dye wool or silk with saffron the material must first be mordanted with alum and then soaked into the dye solution until the desired colour is obtained. However, the use of saffron as a dye has now been superseded by synthetics because of the high price of the spice. Scientifically, saffron has been employed as an histological stain as a dye for connecting tissues. It has also been reported that saffron was used as a glaze on burnished tint oil as a cheap but effective substitute for gold in medieval illumination.^{3, 13, 14}

Saffron is also used as a perfume and in cosmetics. Safranal, a pleasantly odoriferous component of saffron develops during the process of drying by hydrolysis of the bitter substance picrocrocin, which is present in the fresh stigmata. The Greeks considered saffron as a sensual perfume. It was strewn in Greek halls, courts, theatres and in Roman baths. In Rome the streets were sprinkled with saffron when Nero entered the city. In the Middle East saffron is used to prepare an oil-based perfume called Zaafran Attar, which is a mixture of saffron and sandalwood. An alcoholic tincture of saffron is sometimes used as a fragrance ingredient particularly in oriental-type perfumes. Saffron is used as a perfume ingredient in many famous perfume brands The spice is also employed in some types of incense. Nowadays the use of saffron in the cosmetic industry is increasing owing to its active substances and to the trend to use natural products in cosmetic formulations.^{3, 13, 14}

5 Functional properties

The Ebers papyrus (ca 1550 BC) mentions saffron as an ingredient in a cure for kidney problems. Hippocrates, Theophrastus and Galen considered it to be an appetite stimulant, an aid for easing digestive disorders and praised its calming effects on infants.³ Saffron is an often quoted folk remedy for various types of cancer.⁷ Extracts of saffron have been reported to inhibit cell growth of human tumour cells. Crocins, the water-soluble carotenoids of saffron, are the most promising components of the spice to be assayed as a cancer therapeutic agent.¹⁵ Due to the presence of crocetin it indirectly helps to reduce cholesterol levels in the blood. This finding was connected with the low incidence of cardiovascular disease in parts of Spain where saffron is liberally consumed almost daily.³ In small doses it is considered anodyne, antihysteric, antiseptic, antispasmodic, aphrodisiac, balsamic, cardiotonic, carminative, diaphoretic, ecbolic, emmenagogue, expectorant, nervine, sedative, stimulant, and stomachic.⁷

In India saffron is used as a herb in Ayurvedic medicines which heal a variety of diseases ranging from arthritis to impotence and infertility. Saffron is also employed to cure asthma and coughs, useful for colds, to treat alcoholism and to treat acne and skin disorders. It is known to have aphrodisiac properties and is widely employed in Asia and the Middle East as such. Chinese and Tibetan medicine also find many uses for saffron. In India, the spice is used for bladder, kidney and liver ailments and also for cholera.¹⁴ Mixed with ghee it is used for diabetes.⁷ In Indian Unani medicine it is used to reduce inflammation, for treatment of enlarged liver and in infection of the bladder and kidneys. As an ingredient in recipes it is useful in menstrual disorders, for strengthening the heart and as a refrigerant for the brain. If soaked overnight in water and administered with honey it acts as a diuretic. Pounded with clarified butter it used for treating diabetic patients.¹⁴

Saffron blended with opium, cinnamon and clove, commonly known as laudanum was once used as an analgesic and antidiarrhoeic agent.¹⁶ Also mixed with cinnamon, orange peel, rose petals, honey and egg yolk it was employed in ancient Iran as a tonic to restore the strength of the body.¹⁷ Preparations based on the stigmata may be used topically to relieve teething pains in children. Overdoses of saffron (>5g) are narcotic, and saffron corms are toxic to young animals. Apoplexy and extravagant gaiety are possible aftereffects. Fatalities have resulted from the use of saffron as an abortifacient.⁷

6 Quality issues

The most common adulteration practices of saffron are as follows:^{18, 19}

1. The place of origin is falsified. For instance, saffron from different Spanish areas or from different countries is sold as saffron Mancha, one of the best-quality saffrons in the world.

2. The spice is mixed with extracted saffron, old saffron or with style material from the saffron flower.

3. Other parts of the saffron flower are added, stamens or dyed perigonia cut into strips.

4. Some substances are mixed to increase the weight. Moisture, syrups, honey, glycerine, oils, barium sulphate, calcium carbonate, gypsum, potassium hydroxide, saltpeter, Glaubers salt, Seignettes salt, borax, lactose, starch or glucose are commonly used.

5. Other plants are added. These include dried petals of safflower (American or

Mexican saffron, Carthamus tinctorius L.) and Scotch marigold (Calendula

officinalis L.); stigmata from other species of Crocus, usually shorter and without colouring properties, such as Crocus vernus L.and C. speciossus L. Flowers of poppies (Papaver rhoeas L.); pomegranate (Punica granatum L.), arnica (Arnica montana L.) and Spanish oysters (Scolymus hispanicus L.); stamens of some species of carnation (Dianthus sp.), ground red pepper (Capsicum annuum L.); herbaceous plants cut into pieces and dyed; small roots of leeks (Allium porrum L.), red sandalwood dust (Pterocarpus santalinus L.), logwood particles (Haematoxylon campechianum L.) and curcuma (Curcuma longa L.).

6. Sometimes fibres of salted and dried meat are added.

7. Artificial products such as coloured gelatin are added.

8. Organic colouring matters such as Martius yellow, tropeolin, fuchsin, picric acid and colouring products derived from tar.

As saffron is the most expensive of spices, quality control regulations have been proposed in an attempt to avoid these adulterations. The ISO (International Standards Organization) standards are the quality control regulations currently applied in the international saffron business.²⁰ These standards specify microscopic and chemical requirements. Aqueous extracts of saffron are submitted to spectrophotometric scan. Three maximum values are considered which, according to the ISO standards, correspond to the colouring components (crocins at 440 nm), bitter constituents (picrocrocin at 257 nm) and volatile fragrances (safranal at 330 nm). In order to improve this method, high performance liquid chromatography with photodiode array detection (HPLC-DAD) has been used to separate picrocrocin, cis/trans crocins and safranal. This method coupled with mass spectrometry is suitable for the determination of picrocrocin, safranal and

Table 2 ISO standards 3632-1 1993, Chemical requirements

Specifications Stigmata Powdered

Total ashes (%) (w/w), dry matter, max. 8 8

Moisture and volatiles (%) (w/w), max. 12 10

Insoluble ashes in acids (%) (w/w), dry matter, max.

Categories I and II 1.0 1.0

Categories III and IV 1.5 1.5

Water solubility (%) (w/w), dry matter, max. 65 65

Bitterness, picrocrocin absorbance at 257 nm, dry matter, min.

Category I 70 70

Category II 55 55

Category III 40 40

Category IV 30 30

Safranal absorbance at 330 nm, dry matter, all categories

Min. 20 20

Max. 50 50

Colouring strength, crocins absorbance at 440 nm, dry matter

Min.

Category I 190 190

Category II 150 150

Category III 110 110

Category IV 80 80

Crude fibre (%) (w/w), dry matter, max. 6 6

Total nitrogen (%) (w/w), dry matter, max. 3.0 3.0

Source: Adapted from International Standards Organization, Geneva, 1993.