Turmeric--chemistry, technology, and quality.

Turmeric is a minor spice in the West, but a major one in the East. It is valued by Westerners mainly, if not solely, on account of its color, but to the Asians both color and aroma are equally important. This review critically appraises the existing knowledge on the chemistry of the functionally important constituents, the processing of the spice into wholes, powder, and oleoresins, and the objective methods and standards available for evaluation of quality. The importance of the mild (but persistent) aroma, and the lack of detailed knowledge on the significant volatiles are discussed. Some unpublished data on significant aroma components, a tristimulus study of color, and subjective evaluations of quality are summarized. Other areas briefly discussed are the production and trade, curry powder, allied spices, and biosynthetic and physiological aspects. The confusion existing in the literature on the nomenclature of species included in the genus Curcuma is pointed out. In view of the growing importance of turmeric and its extracts as a natural food color, recent results on toxicological aspects are discussed. The areas in which research is needed are indicated at the end.