The bright color of curry in the cooking of India is turmeric. The color, sometimes called curcuma, is a fluorescent yellow extract from the roots of several species of the ginger family, The major chromaphore of the extract is called curcumin. The emulsified form has an intense color (about 4 times that of a typical FD&C dye) and a small amount, in the range of 5 to 20 ppm, is sufficient to color a product system. Turmeric has the closest hue to FD&C Yellow No. 5 and is a viable substitute. A major limitation of turmeric extract is its instability to light. It has good thermal stability and is not affected by pH until the system is quite alkaline. It complexes with protein, is highly resistant to oxidation and is believed to have antioxidant properties equivalent to BHA/BHT. The presence of cations appears to move the color to orange-brown. In acidic systems, the color is lemon-yellow with a characteristic green florescence. As the pH increases, the green tint diminishes and ultimately the hue becomes orange.
pH range: 2-14
Color range: yellow to dark brown.