Extraction of polyphenolics from plant material for functional foods - Engineering and technology

Polyphenolic substances or polyphenols include many classes of compounds ranging from phenolic acids, colored anthocyanins, simple flavonoids, and complex flavonoids. Polyphenolics contribute to the bitterness and astringency of fruits and fruit juices due to the interaction between polyphenolics, mainly procyanidins, and the glycoproteins in saliva. Polyphenols contribute largely to cellular processes within the body. In terms of pharmacological activity, they act against the oxidation of high-density lipoproteins (HDLs). Hence, they help the body retain important HDL while helping it get rid of problematic low-density lipoproteins (LDLs). In addition, polyphenols have also been found to have antiulcer, anticarcinogenic, and antinuitagenic activities. The reason behind these activities is polyphenol's strong antioxidant power because they are able to quench free radicals. Green tea and grape seed extracts provide a superior source of monomers that are relatively inexpensive to extract. Comparatively, pine bark and otherfruits extracts have low levels of monomers. Therefore, the nutraceutical industry has focused on optimizing extraction processes for green tea leaves and grape pomace, skins, and seeds. During extraction, a solvent is mixed with the plant material (grape seeds, grape skins, pine bark, or tea leaves). Extraction can be either completed by the addition of a solvent to the sample in a container and then removed by drying, or the solvent can be removed by concentration by ultrafiltration (UF). After any one of these processes, the extract must be dried to obtain a powderform. Alternatively, supercritical fluid extraction (SFE) can also be used, which produces the final product as a powder without any use of final drying. Organic solvent extraction is efficient and simple, yet costly. Large amounts of organic solvents are needed. This, in turn, is also detrimental to human use because traces of the organic solvent are present in the polyphenol extract. Polyphenol separation and concentration by membrane separation is even more efficient than organic solvent extraction. Organic solvents are still used but in lower quantities, and UF ensures the purity of the polyphenol extract. The drawback is membrane fouling, which can disrupt the process, and the time it takes to complete the process. The separation process has to be repeated several times. Supercritical fluid extraction is the extraction process of the future. CO2 is low cost, nontoxic, nonflammable, and noncorrosive, making it the perfect solvent for natural products. In the U.S. inarket, where $141 Million was spent on grape seed products in 1999, it is imperative that safe and efficient extraction procedures are delivered that guarantee a pure polyphenol product.