Saffron: the brightly coloured spice from crocus flowers

Saffron is made by drying stigmas from Crocus sativus flowers. Image by Safa Daneshvar (CC-BY-SA-3.0) via Wikimedia Commons

Saffron is the world’s most expensive spice by weight. Its vibrant orange-red colour means that as well as being used for flavouring food, it can also be used to dye fabric. Saffron comes from the stigmas (female part) of Crocus sativus flowers. Each stigma is hand-picked, dried and then sold whole or as saffron powder. Since each flower only contains 3 stigmas, around 150,000 flowers are needed to make 1 kg of saffron (1).

Crocus sativus. Image by Liné1 (CC BY-SA 3.0) via Wikimedia Commons

C. sativus is an autumn-flowering perennial. It has been cultivated for over 3000 years and today is grown across the world in countries including Spain, Iran, Afganistan, India, Tibet and China (2). Spain and Iran are the biggest producers accounting for over 80% of production (2). The species does not exist in the wild, and is thought to be descended from the Mediterranean autumn-flowering crocus C. cartwrightionus (2).

C. sativus is triploid, meaning that its genome has three copies of each chromosome instead of the more typical two (diploid organisms like us humans). This makes C. sativus infertile because its chromosomes don’t pair up properly during meiosis (cell divisions that produce sperm and egg cells for sexual reproduction). In the absence of sexual reproduction, C. sativus is propagated vegetatively, by digging up and separating the corms (bulb-like storage organs) before replanting.

The vibrant orange-red colour of saffron is due to the presence of carotenoid compounds, primariliy crocin (4). The bitter taste is due to picrocrocin, a breakdown product of the carotenoid zeathanin (3). When C. sativus stigmas are dried, some of the picrocrocin is converted to safranal, which is largely responsible for the “hay-like” aroma of saffron (3). Historically, C. sativus was highly valued as a medicinal plant, and evidence is emerging that some of the compounds in saffron may have medicinal properties, including as antioxidants, cancer treatments or anti-depressants.

Workers picking saffron in Iran. Image by By Safa Daneshvar (CC-BY-SA-3.0) via Wikimedia Commons.

References:

1) Laws (2010) Fifty plants that changed the course of history. David and Charles.

2) Rubio-Moraga (2009). Saffron is a monomorphic species as revealed by RAPD, ISSR and microsatellite analyses. BMC Res Notes.

3) Wikipedia: Saffron. http://en.wikipedia.org/wiki/Saffron (retrieved 16/04/14)

4) Wikipedia: Crocin. http://en.wikipedia.org/wiki/Crocin (retrieved 16/04/14)