The extraction methods of natural pigments include solvent extraction, microwave extraction, ultrasonic extraction, supercritical fluid extraction, etc. Currently, most of the extraction methods for Gardenia Yellow Pigment are solvent extraction.
1. Solvent extraction method
1) Raw materials: The content of crocin and geniposide in water gardenia is generally higher than that of mountain gardenia. The content of crocin in the aged gardenia fruit is very little, the color is no longer yellow, and the relative content of gardenia is very high. In addition, the content of crocin in the kernel is higher than that in the whole fruit, and the content of geniposide and chlorogenic acid in the husk is relatively high. Therefore, when extracting Gardenia Yellow Pigment, it is more beneficial to remove the old fruit and extract after dehulling. Improvement in pigment quality.
2) Solvent Crocodin, crocin, crocin and geniposide are all water-soluble polar molecules. The experiment found that alcohol is beneficial to the extraction of crocin and crocin, and water is beneficial to the extraction of geniposide. It is not advisable to use high-concentration ethanol for extraction, otherwise fats, hydrocarbons and more green-stained substances will dissolve with the pigment, and 50% or 60% ethanol is appropriate. Extraction with organic solvents is costly and has certain risks in production, and organic solvents are not conducive to microwave extraction and resin adsorption, which increases the difficulty of the refining process. The extraction process with water is simple, but the extraction time is relatively long, and the extracted pigment impurities are many. If hot water is used for extraction, protease and amylase can be added in the process to promote the dissolution of pigments. The oil content affects the efficiency of pigment extraction, and pre-degreasing before extracting pigment is beneficial to pigment leaching. Acid-added solvents can improve the solubility of pigments, but reduce their stability.
3) Solid-liquid ratio In order to reduce the amount of solvent and the burden of subsequent processes, the dry weight of the fruit (g): the volume of the solvent (ml) is generally 1:6 to 1:12. If the ratio of material to liquid is too large, more energy is consumed for concentration and drying. If the ratio of material to liquid is too small, the extraction of pigments is insufficient, and the filtration of the extraction liquid is also very difficult.
4) Extraction temperature The research shows that 50℃～60℃ is the ideal extraction temperature. If the temperature continues to rise, the increase of the pigment extraction rate is not large, and the high temperature is easy to cause pigment loss. When the extraction temperature is too low, the obtained product is not easy to dry and is easy to deliquescence.
5) Extraction time When water is used as the extraction solvent, especially at room temperature, the extraction time needs more than 12 hours, or even 2 to 3 days. Extraction with organic solvent aqueous solution takes no more than 4 to 5 hours to complete the extraction.
6) Number of extraction stages After the extraction stage is higher than 3 times, the extraction rate of pigments will not increase significantly, and the extraction stage should be selected 2 to 3 times. The five related factors extracted from Gardenia Yellow Pigment were ranked in descending order of their influence on absorbance: fruit crushing particle size, extraction times, extraction temperature, extraction time and solid-liquid ratio, among which fruit crushing degree and extraction times were significant effect factors. The five factors were ranked from large to small for the extraction of pectin: extraction temperature, fruit crushing degree, extraction times, extraction time and solid-liquid ratio, among which fruit crushing and extraction temperature were significant effect factors. After comprehensive optimization of 5 influencing factors, the extraction rate of Gardenia Yellow Pigment can reach 95.13%.