Paik Y, Lee C, Cho M, Hahn T
Department of Chemistry and Genetic Engineering, and Plant Metabolism Research Center, Kyung Hee University, Suwon 449-701, Korea.
J Agric Food Chem. 2001 Jan;49(1):430-2. doi: 10.1021/jf000978f.
Fruits of Gardenia jasminoides contain geniposide which can be transformed to blue pigments by a simple modification. Colorless geniposide obtained from gardenia fruits by charcoal and silica gel column chromatographies was hydrolyzed with beta-glucosidase to yield genipin. The resulting genipin was transformed to blue pigments by reaction with amino acids (glycine, lysine, or phenylalanine). The stability of the blue pigments against heat, light, and pH was studied to examine the blue dye for possible use as a value-added food colorant. Thermal degradation reactions at temperatures of 60-90 degrees C were carried out at different pH levels within the range 5.0-9.0 (pH 5.0, acetate buffer; pH 7.0, phosphate buffer; and pH 9.0, CHES buffer). The blue pigments remained stable after 10 h at temperatures of 60-90 degrees C, and in some cases, more new pigments formed. The pigments were more stable at alkaline pH than neutral and acidic pH. Similarly, the pigments were stable under light irradiance of 5000-20 000 lux. In this case, pH effect was not significant.
栀子果实含有京尼平苷，通过简单的改性可将其转化为蓝色色素。通过活性炭和硅胶柱色谱法从栀子果实中获得的无色京尼平苷用β-葡萄糖苷酶水解生成京尼平。所得京尼平通过与氨基酸（甘氨酸、赖氨酸或苯丙氨酸）反应转化为蓝色色素。研究了蓝色色素对热、光和pH的稳定性，以检验该蓝色染料作为增值食用色素的可能性。在60 - 90℃的温度下，于5.0 - 9.0范围内的不同pH水平（pH 5.0，醋酸盐缓冲液；pH 7.0，磷酸盐缓冲液；pH 9.0，CHES缓冲液）进行热降解反应。蓝色色素在60 - 90℃的温度下10小时后仍保持稳定，在某些情况下，还形成了更多新的色素。色素在碱性pH下比中性和酸性pH下更稳定。同样，色素在5000 - 20000勒克斯的光照下也很稳定。在这种情况下，pH效应不显著。
