Crocin

Saffron boiled in water for 20 min kept most of its colour compounds. Crocin stood at 81 per cent of its uncooked level, tricrocin at 74 per cent and crocin-3 at 93 per cent, and the total of the measured crocetin compounds at 88 per cent. The minor compound crocetindial disappeared.

Saffron heated in olive oil at 180 °C for 5 min lost about two thirds of its colour compounds: the total fell to 36 per cent of the uncooked level. Crocin dropped to 66 per cent and tricrocin to 26 per cent, while crocin-3 rose slightly and two compounds absent from raw saffron appeared, crocetin and its 13-cis isomer. The pattern is that of the sugars being split from the crocins, followed by partial isomerisation of the crocetin released.

Cooked into rice dishes, saffron’s colour compounds were recovered at far lower levels than from saffron cooked alone. A paella-type dish, saffron boiled with rice for 20 min, returned about 20 per cent of the original total; a pilaf-type dish, in which saffron was first fried with the rice in oil and then boiled, returned about 8 per cent and no detectable crocin, most of what remained being crocetin. The authors state that what becomes of the missing compounds is not yet known.

The crocins of ground saffron moved into water and hardly at all into oil. The highest yield in the main series, 85.4 µg per mg of saffron, came from water at 60 °C after 20 min; hotter water and a longer infusion of 30 min both gave less, while pure olive oil never took up more than 3.1 µg/mg. In a further series at lower temperature, water at 20 and 40 °C extracted crocins better than water at 60 °C, and the authors conclude that heating is not needed to extract the colour.

When the drying time at a given setting was lengthened, crocin and picrocrocin in saffron barely moved while safranal swung widely. In an electric oven at 50 °C, extending drying from 50 to 65 min raised crocin by 1.81 per cent and safranal by 26.90 per cent. At 60 °C, going from 45 to 60 min raised crocin by 1.13 per cent but cut safranal by 23.13 per cent; at 70 °C, 30 to 45 min raised safranal by 13.18 per cent. In a microwave at 600 W, doubling the time from 3 to 6 min cut safranal by 58.59 per cent and crocin by 1.10 per cent while the picrocrocin peak rose by 13.84 per cent. The authors explain the pattern as formation and degradation proceeding at once, at rates that depend on temperature.

Saffron from a single farm, harvested in different years and kept in zip-lock bags at room temperature, had lost 52.2 per cent of its crocetin esters and 54.3 per cent of its picrocrocin after the first year. The rate of loss then slowed over the following years. The individual pigments did not move together: the two main trans esters fell every year, while two minor ones fell, rose and fell again. On the basis of these data the authors suggest that saffron of this origin should not be kept for more than two years.

Comparing freshly dried saffron with saffron stored for two years, the authors found that the fresh samples held more of the crocins, of picrocrocin and of two minor volatiles, while the stored samples held more safranal. They conclude that during storage the intensity of saffron’s colour falls while its aroma compound increases, the two moving in opposite directions.