Key Technology of Grape Seed Extract Proanthocyanidins Production
In 1967, 4 kinds of polyphenols were extracted and separated from grape skins and grape seeds in the United States and Joslyn. They were heated in acid medium and can produce anthocyanin, so the polyphenols were named Proanthocyanidin. These compounds are the main functional substances in grape seed extract, and have many biological activities. It has been widely used in the fields of food, medicine, cosmetics and so on.
Proanthocyanidins can significantly improve the anti-aging ability of the body, improve cardiovascular function, prevent hypertension, enhance the human body's ability to resist mutagenesis, and even have therapeutic effects on atherosclerosis, gastric ulcer, bowel cancer, cataract, diabetes, heart disease, arthritis and other diseases. Tracing to the source, the most important and fundamental role of procyanidins is to eliminate excess free radicals in the body, and other functions should be derived from it.
The extraction and separation of anthocyanins from grape seeds can be extracted and separated by methanol, ethanol, acetone, and other polar solvents. The extract is extracted with ethyl acetate and other solvents. The extract is separated by column chromatography, which can be used as dextran gel column chromatography, chiral adsorption column chromatography and high-performance liquid chromatography. In proanthocyanidins, the antioxidant activity of oligomeric proanthocyanidins (OPC), especially two polymers, is the most important, so the content of oligomeric proanthocyanidins in grape seed extract has become the key index for the quality of the product.
Extraction of Proanthocyanidins:
Grape seed is a by-product of wine, accounting for 4% to 6% of the whole grape. The content of proanthocyanidins in grape seed hull is much higher than that in kernel. At present, the first degreasing extraction process is widely used. The degreasing method will affect the extraction rate and quality of proanthocyanidins. The degreasing methods include press method, solvent method and supercritical C02 extraction method. Squeezing method is rare because of its low extraction rate and waste. The solvent method is the most commonly used method at present. The equipment is simple, the cost is low, and the extraction rate is considerable. In addition, supercritical C02 extraction can reduce the decrease of polymerization degree in other extraction methods, because there is no interference between light and air. Tipsrisukond et al reported that the extract obtained by supercritical C02 extraction was much more antioxidative than traditional methods, and the extract did not need to concentrate. But this method has the higher requirement for technology and is not easy to popularize at present.
After the separation of oil, the organic solvent such as ethanol or acetone is usually used to extract the seed shell. The obtained shell residue is heated to remove the solvent and the solvent can be recycled. The crude extracts of proanthocyanidins can be obtained by filtration and spray drying.
Purification of Proanthocyanidins:
Extraction of Procyanidins from crude extracts can be classified by solvent extraction fractionation, activated carbon adsorption and separation, macroporous resin adsorption chromatography. There are also lead acetate precipitation, polyvinylpyrrolidone (PVP) adsorption method and other refining methods, but the former must remove lead, tedious and time-consuming, lead removal will not be completely affected food; the latter is expensive and uneconomical. The solvent extraction method is simple and time-saving. It is a good method for the purification of Proanthocyanidins from grape seed. The adsorption chromatography method can increase the purity of the solvent elution product to more than 90%, and the eluent is more suitable for functional food and medicine than crude extract.
Solvent fractionated refining:
A certain amount of crude proanthocyanidins were obtained by adding alcohol-water to form a solution, and then the ethyl acetate was used for fractionation and extraction. The proportion was 1: 3.5 (proanthocyanidin solution: ethyl acetate). The water layer is extracted with n-butanol. The contents of proanthocyanidins in the extract A1, A2 and A3 were 4.85%, 3.56%, and 3.34% respectively after the vacuum drying of ethyl acetate extract A1, n-butanol extract A2 and n-butanol extractive A3 after vacuum drying.
Active carbon adsorption:
The content of proanthocyanidins in the adsorbent of activated carbon is very high, but its antioxidant effect is far less than that of ethyl acetate extract in solvent fractionation.
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