In the KitchenA fat-soluble molecule, curcumin constitutes roughly 1 to 6 percent of turmeric’s dry weight. Curcumin is extremely sensitive to light, moisture, and heat. Roughly 85 percent is destroyed when turmeric is boiled for 15 to 30 minutes. Furthermore, it degrades rapidly (within 30 minutes or so) at a neutral pH

Source: Be Smart When Cooking with Turmeric