Saffron is a food spice obtained from the flower stigmas of Crocus sativus a member of the Iridaceae family. It plays an important role in the culinary culture of different regions of the world, where it is used as a food additive, since it possesses powerful coloring and flavoring properties. As the most expensive foodstuff in the world, saffron is being known for its unique characteristics which are very important in garnishing the dishes and foods.
Scientifically the most important factors in evaluating the quality of saffron are crocin, picrocrocin and saffranal. Crocin is the one which is measured, because it is a precursor to the other compounds, which together produce the three things Chefs all around the world are looking for: AROMA (Saffranal), Flavor (Picrocrocin) and Color (Crocin), all of which can be measured using UV-VIS absorbance.
The spice gains its vibrant yellow-red color from crocin, an ester of the carotenoid crocetin, causing a strong absorbance peak at 440 nm. Saffron’s flavor can be attributed to picrocrocin, measured via the ISO standard at 257 nm. The characteristic scent of saffron comes from safranal, which is generated from picrocrocin as a result of combined heat and enzymatic action during the drying process, and is monitored at 330 nm. Though the balance of all three compounds is ultimately determines how highly a saffron will be rated, the crocin levels or “coloring strength” at 440 nm is the lead indicator for quality and often price.
In other words, Higher coloring strength means higher quality saffron. Generally, the coloring strength is presented by two or three digit number such as 95 or 180 or 235. The higher number represents higher quality saffron. According to ISO (International Organization for Standardization), any saffron with coloring strength of 190 and above is called GRADE I saffron which is a good quality saffron.
Curious to see how the concentration of these compounds might vary amongst brands, there were tested four different sources of saffron, ranging from freshly opened to 18 years old. you can read all report here.
What are the signs of good quality saffron?
Good quality saffron is saffron which has a decent coloring capabilities and has a pleasant aroma. Saffron’s coloring capabilities come from the red portion of the saffron threads and not the yellow portions that are left uncut in lower grade saffron. Therefore a good quality saffron is a saffron that is all red. This criterion is necessary but not sufficient. For example, an all red saffron that is 10 years old is not a good quality saffron. The next criteria is aroma. Old saffron looses its pungent aroma and sometimes it has no aroma at all. So, a good quality saffron is saffron that is completely red and has a nice aroma.
At the end remember, variation in relative crocin, picrocin, and safranal levels between samples is to be expected due to differences in climate, soil, and growing conditions, and on the specific cultivation & processing techniques passed down from one generation to the next. Of all these, the drying process has the greatest impact on quality, as drying initiates the chemical changes needed to develop the lead flavor component, safranal, influencing the balance between color, bitterness, and aroma that is the pride of producers of high quality saffron. Some producers choose to dry their saffron over almond charcoal using a sieve, while others use olive or oak, varying the drying time with the depth of the layer of saffron and the eye of experience, employing as much art as science.