TABLE 4.

Stability of blue natural dyes under the influence of common environmental factors: temperature, pH, and light radiation¹

Dye	Temperature	pH	Light
Gardenia Blue	Sensitivity to high temperatures above 80°C	Resistance to environmental pH changes	High resistance to light radiation
Phycocyanin	Very high sensitivity to elevated temperature (protein denaturing process). Above 55°C, its content dropped by more than 60% after 5 minutes of heating	Slightly sensitive to changes in the pH of the environment	Medium light resistant (after 5 h of exposure; 3.28×105 lux): content drop is about 30% in pH 5 and about 40% in pH 7
Anthocyanins	Not resistant at high temperatures	Very sensitive to pH changes. Changing the pH causes a change in color	In an alkaline environment, they are resistant to light rays
Natural Indigo	Stable to 90°C in MCT oil (obtained by extraction of coconut oil) for 5 days	Insensitive to pH changes (insoluble in water)	Low light–resistant (after 5 h of irradiation; 3.28×105 lux): the content decrease is about 70%

¹Information used in compiling the table is from Krępska et al. (6). MCT, medium-chain triglycerides.