Saffron agents. It must, therefore, be stored away in air-tight containers to minimise contact with atmospheric oxygen. Saffron is somewhat more resistant to heat. Saffron is not all of the same quality and strength. Strength is related to several factors including the amount of style picked along with the red stigma. Age of the saffron is also a factor. More style included means the saffron is less strong gram for gram, because the colour and flavour are concentrated in the red stigmas. Saffron from Iran, Spain and Kashmir is classified into various grades according to the relative amounts of red stigma
Trade and use of saffron well-to-do monks wore a long linen undershirt known as a "léine", which was traditionally dyed with saffron. In histology the hematoxylin-phloxine-saffron (HPS) stain and Movat's pentachrome stain are used as a tissue stain to make biological structures more visible under a microscope. Saffron stains collagen yellow. There have been many attempts to replace saffron with a cheaper dye. Saffron's usual substitutes in food—turmeric and safflower, among others—yield a garishly bright yellow that could hardly be confused with that of saffron. Saffron's main colourant is the carotenoid crocin; it has been discovered in the less tediously harvested—and hence less costly—gardenia fruit.