Microwave-assisted extraction of bioactives in fruits and vegetables: a comprehensive review

Fruits and vegetables are integral parts of the daily diet and consist of inedible peel, pomace, and kernel, which are rich in bioactive compounds (BACs). These BACs can be extracted by microwave-assisted extraction using microwave energy. Microwaves are non-ionising electromagnetic radiations with a frequency range of 300 MHz to 300 GHz. Its instrumentation includes a magnetron, waveguide, applicator, and circulator. Microwave extractors are of two types: open and closed. The former is used to extract thermoinsensitive compounds, and the latter to extract thermolabile compounds. Microwave extractors work with dual mechanisms called dipolar rotation and ionic conduction. They help to rupture the cell wall and release BACs into the solvent. The factors viz., solvent type and concentration, microwave power, extraction time, solvent-to-sample ratio, extraction temperature, and sample properties affect the extraction efficiency. Microwave-assisted extraction provides benefits such as higher yields, low extraction time, low solvent consumption, and compatibility with other methods.