Sato Kyoko, Maitani Tamio
National Institute of Health Sciences: 1-18-1, Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan.
Shokuhin Eiseigaku Zasshi. 2003 Feb;44(1):73-6. doi: 10.3358/shokueishi.44.73.
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.
天然食用色素栀子红是通过环烯醚萜苷甲酯水解制得的。栀子蓝也是由环烯醚萜苷制成的。因此，市售产品有可能含有甲醇。为测定栀子红和栀子蓝中的甲醇，建立了标准加入顶空气相色谱法。对于含有甲酯的栀子蓝，在甲醇分析过程中可能会生成甲醇。因此，研究了在顶空气相色谱法中不产生甲醇的条件。将含有1 g色素制剂、1 mL水和标准溶液的小瓶密封。平衡温度是分析栀子蓝中甲醇条件中的一个重要因素。虽然在室温及50℃时甲醇含量相等，但在80℃时含量增加了1.2倍。在50℃下测定的两种栀子红产品中的甲醇含量分别为8和9微克/克，三种栀子蓝产品中的甲醇含量为25 - 34微克/克，均低于许多其他天然食品添加剂规定的50微克/克的残留限量。
