Saffron: The Complete Guide
Saffron is three red threads from the center of a crocus flower, dried. That is the whole ingredient. Each flower gives up exactly three stigmas, the flowers open once a year over a few weeks in autumn, usually October and November, and it takes roughly 150 to 170 of them, picked by hand, to make a single gram of spice. All of that is hand work, and because of saffron's high price and the constraints on producing it, the spice is often a target for adulteration. This guide follows those threads from the corm to the kitchen cupboard, with a grading table and a thread-to-milligram conversion along the way. For a first dish, start with the saffron recipe to learn first.
The plant grown from corms
The saffron crocus is Crocus sativus, which some reports describe as a sterile triploid that does not set fertile seed; saffron is grown from corms, the small bulb-like bases of the plant, which growers divide and replant. Growers set the corms about three inches deep in late summer or early fall, and the flowers come up in late October and early November. University of Vermont Extension rates it to USDA Zone 6 and, citing the university's own research, notes that it readily survives in Zones 5 and even 4.
Iran is by far the world's largest grower. Saffron is also grown in Afghanistan, Spain, Greece and India, among other countries. Wherever it grows, there is one short bloom a year, and in La Mancha the flowers are picked every day it lasts.
From flower to thread
University of Vermont Extension advises harvesting on a dry, sunny day, early to mid-morning. Pickers take the whole flower, and the three stigmas are then pulled from each blossom by hand. Under the La Mancha rules, the stigma is separated from the style at the point where the style begins to turn white, and the finished spice must show a stigma at least twice as long as any style left attached. The style is the stalk the stigma grows from, and the rules allow a short length of it to stay on the thread.
Then the threads are dried. Safranal, the compound behind much of saffron's aroma, develops during drying, probably when the bitter compound picrocrocin breaks down through enzymes or heat. In La Mancha the threads are toasted: held over indirect heat from a brazier or stove for 20 to 45 minutes. The designation's specification credits this low roasting with its strong aroma and safranal content, and its official sensory description calls the smell clean, intense and pungent, with toasted notes.
Color, bitterness and smell: the three compounds
Saffron's color, taste and smell come mainly from three substances, and the international trade standard estimates all three.
Crocin is the color. It is a carotenoid pigment made water-soluble by two attached sugar groups, which is why saffron colors water so readily, and it may make up more than 10 percent of dry saffron's weight. Picrocrocin is the taste, a bitter glycoside. Safranal is the smell, probably formed from picrocrocin during drying. Safranal is poorly soluble in water, while the color compounds dissolve readily.
Saffron contains more than 150 volatile and aroma-yielding compounds in all, but the concentration of these three is what determines its commercial quality.
How saffron is graded
International trade in saffron runs on ISO 3632, a standard that sorts the spice into trade categories by laboratory test. A measured amount of saffron is steeped in water, and the extract's light absorbance is read at three wavelengths: 440 nanometers for coloring strength (crocin), 257 for bitterness (picrocrocin) and 330 for aroma (safranal). The standard also sets test methods for moisture, floral waste such as styles and stamens, and foreign matter. Food chemists at Aristotle University of Thessaloniki have pointed out the method's limits, particularly that the 330 reading does not fully capture safranal because safranal dissolves so poorly in water. The method remains the common language of the trade.
Azafrán de La Mancha, the Spanish protected designation of origin, sets its own thresholds, tested by the ISO methods:
| Measure | What it measures | La Mancha PDO requirement |
|---|---|---|
| Coloring strength, 440 nm | Crocin: how much gold the threads give | Above 200 |
| Bitterness, 257 nm | Picrocrocin: the saffron taste | Above 70 |
| Aroma, 330 nm | Safranal: the saffron smell | Above 20 |
| Moisture and volatile matter | How well the threads were dried | Below 11 percent |
| Floral waste | Styles, stamens, petals, pollen | 0.5 percent or less by weight |
| Foreign matter | Anything not from the flower | 0.1 percent or less by weight |
| Stigma to style length | How the threads were cut | At least 2 to 1 |
| Artificial colorants | Adulteration | Must pass the test for artificial colorants |
La Mancha saffron may be sold only as threads, never powder, and every container carries a numbered guarantee seal or label issued by the control body. The first two letters of the code on the label identify the year the saffron was produced.
Threads, flowers and milligrams
Recipes measure saffron in pinches, threads and grams, which do not convert neatly into one another. The table below converts between threads, weight and flowers. It starts from the University of Vermont figure of 150 to 170 flowers per gram and three stigmas per flower, which puts a gram at roughly 450 to 510 threads and a single thread at about 2 milligrams. Thread weight varies with length and with how much style is left on, so these are working estimates, not lab values.
| Amount | Threads, approximately | Flowers it took |
|---|---|---|
| 1 thread, about 2 mg | 1 | A third of a flower |
| 40 mg | 18 to 20 | 6 to 7 |
| 0.1 g | 45 to 51 | 15 to 17 |
| 0.2 g | 90 to 102 | 30 to 34 |
| 0.5 g | 225 to 255 | 75 to 85 |
| 1 g | 450 to 510 | 150 to 170 |
The 0.2 gram row has a reference point. In the La Mancha designation's sensory test, 200 milligrams of crushed, sieved threads are steeped in a liter of water, and the result is described as bright, clear and yellow with light orange tones, tasting toasted, gently bitter and gently pungent. That works out to 20 milligrams, about 9 to 10 threads, per 100 milliliters.
How to buy saffron
Know what fraud looks like. The substitutes documented in the scientific literature include safflower and marigold petals, corn silk, the crocus's own styles and stamens, strips of petal, and artificial colorants.
Read the origin. A label that names a country, and a region or designation such as La Mancha where one applies, tells a buyer where the threads were grown.
Burlap & Barrel's Herati saffron (shop Herati Saffron) takes its name from Herat, and the Burlap & Barrel producer guide covers the company's work with the saffron farmers there. The single-origin spices guide explains the model more broadly.
How to cook with saffron
Steep it first. Crocin is water-soluble, so the color needs liquid to move out of the thread. Crush the threads and let them sit in a little warm stock, water or milk before they go into the dish. In the La Mancha designation's sensory test, the crushed, sieved threads steep for 20 minutes at about 60°C, 140°F, which is warm, not boiling. Add the liquid and the threads together. The guide to toasting and blooming spices covers the general technique.
Add it where the liquid is. Saffron's color travels through water, so it suits dishes with liquid in them: rice, stock, sauce, dough. It is at home in yellow rice and in bouillabaisse, and in enriched breads such as the ones in the saffron buns recipe. In Italy it goes into risotto: the risotto alla milanese recipe walks through the dish, and the risotto rice guide covers the rice.
Try it sweet. Saffron also goes into preserves: Brins pairs it with lemon in its Lemon Saffron Marmalade (shop Lemon Saffron Marmalade).
How to store saffron
Saffron keeps best in an airtight container, out of direct sunlight and away from heat. The La Mancha rules require the dried spice to be stored in a cool, clean, well-ventilated place below 25°C, 77°F. The guide to whether spices expire covers how to judge an old jar.
Sources & Further Reading
- University of Vermont Extension: Saffron, the world's most expensive spice
- Srivastava et al., Crocus sativus L.: A comprehensive review, Pharmacognosy Reviews, 2010
- Molecules special issue editorial: Saffron authenticity, quality and bioactivity studies
- Single Document, PDO Azafrán de La Mancha, PDO-ES-0112-AM02
- Japan Ministry of Agriculture GI register: Azafrán de La Mancha, designation 53
- Kyriakoudi, Ordoudi and Tsimidou: Saffron quality parameters in ISO 3632, IMEKO FOODS 2017
- The Pantry Dispatch: Risotto alla Milanese
- The Pantry Dispatch: Single-Origin Spices, Complete Guide
