Methods of Extraction of Phytochemicals in Vegetables

Phytochemicals are chemicals found in plants that offer important health benefits to humans, such as the reduction of oxidative or inflammatory stress. While fruits and vegetables are rich in phytonutrients, it can be useful to consume a particular phytochemical in a more concentrated form. The anti-inflammatory compound, quercetin, which is found in onions is one example. There are several extraction methods that allow access to these medicinal compounds.

Juicing

• The most straightforward way to "extract" phytochemicals from a vegetable is through juicing. By stripping away the extraneous fibers, this process enables you to consume much higher concentrations of the beneficial compound than if you were to eat the vegetable. Drinking a cup of cabbage juice is much easier and more energy-efficient than eating the whole head of cabbage raw. Some phytochemicals, however, like the quercetin found in onions demand more sophisticated methods of extraction.

Homogenization

• Before extraction, vegetables are first ground with a pestle and mortar. They can also be finely chopped or processed in a blender or food processor. This process breaks up the plant cells, preparing the phytochemicals stored inside for release through extraction.

The Role of Solvents

• If the phytochemical is at all soluble, the vegetable matter is then immersed in a solvent with the same polarity as the targeted phytochemical. Alcohol and water, for example, are common high-polar solvents.

Maceration

• In this relatively simple process, the plant tissue is left to sit in the solvent at room temperature, in a closed container. After the solvent soaks up the phytochemicals, it is then decanted and filtered.

Soxhlet Extraction

• This process, used for non-volatile phytochemicals that have limited solubility, intensifies interaction with the solvent through heat and repetition. The solvent is boiled in a flask so its vapors pass up and then liquify through the use of a condenser into a chamber holding the plant sample. The solvent passes through this cycle multiple times, each time extracting more and more of the phytochemical.

Hydrodistillation

• This extraction method is used to capture more volatile compounds. In this process, the plant sample is left to sit in a boiling, water-filled flask that is connected to a condenser, which allows the distillate matter to escape through evaporation for final collection.

Aeration

• Once the compound has been extracted, it is left at room temperature in an aerated space to evaporate any residual solvents. Each process is delicate and complex. A successful extraction requires thorough research that accounts for the polarity, volatility and solubility of the specific phytochemical.