Tuesday, March 11, 2014

Saffron barcoding

Saffron is the dried stigma from a small, purple crocus (Crocus sativus). It is the world’s most expensive spice. That’s because each flower provides only three stigmas, which are picked and dried by hand, and it takes tens of thousand of individual strands to produce one ounce of saffron.  The plant blooms only once a year and the harvest of stigmas, by manual picking, should be performed within very short time. Fortunately, a very little goes a long way. Just one or two threads can add flavour and colour to an entire pot of rice. Saffron imparts a pungent, aromatic flavour and an inten yellow colour to dishes. It is used around the world dating back to ancient Egypt, Greece and Rome where it was used as dye, perfume, spice and even as drug in the traditional treatment of numerous diseases.

Since the middle ages, the high economic value of saffron has caused its adulteration with natural or synthetic substances. As a consequence there are international standards (ISO/Technical Specification 3632 2003) in place to define saffron quality. These standards recommend the use of spectrophotometric and chromatographic analyses to ensure spice color, taste and aroma. However, they do not provide guidance on the issue of species identification.

Given all that it is about time to start using DNA Barcoding as a means to control the species identity of saffron spice products. Collaborative research between Universidad Polit├ęcnica de Madrid (UPM) and the University of de Tor Vergata has now confirmed that the DNA Barcode standards for plants work well with a variety of Crocus species. This proof of concept study also allowed some insight into the mystery of the origin of Crocus sativus, a sterile, triploid species. A number of morphological studies support the theory that it would have been originated through hybridization of other Crocus species, especially Crocus thomasii, Crocus hadriaticus and Crocus cartwrightianus. The study was only able to show that Crocus sativus could have evolved due to a series of independent factors relating to geography. The authors were able to find marked genetic differences between Spanish and the Italian saffron varieties but it seems too early for a final answer. However, the good news is that there is another case we can add to the countless other ones demonstrating the applicability of DNA Barcoding. Societal benefits? Just think of it the next time you eat a good Paella


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