[Determination of methanol in gardenia red and gardenia blue]

The natural food color gardenia red is manufactured through the hydrolysis of the methyl ester of iridoid glucoside. Gardenia blue is also made from iridoid glucoside. Therefore, there is a possibility that the commercial products contain methanol. To determine methanol in gardenia red and gardenia blue, a headspace GC method with standard addition was developed. In the case of gardenia blue with the methyl ester, methanol may be formed during the analytical procedures for methanol. Thus, conditions in which methanol would not be produced in the headspace-GC method were investigated. Vials containing 1 g of the color preparation, 1 mL of water, and a standard solution were sealed. Equilibrium temperature was an important factor among the conditions for analyzing methanol in gardenia blue. Although at room temperature and 50 degrees C, the contents of methanol were equal, the content increased 1.2 times at 80 degrees C. Methanol contents determined at 50 degrees C were 8 and 9 micrograms/g in two gardenia red products and 25-34 micrograms/g in three gardenia blue products, which were below the residual limit of 50 micrograms/g set for many other natural food additives.