Recent advances in extraction of antioxidants from plant by-products processing industries

The by-products obtained from plant processing industries are the cheap source of bioactive compounds especially antioxidants. Extraction of bioactive compounds can be obtained by using conventional and non-conventional methods. Extraction efficiency of any conventional method mainly depends on the choice of solvents. The major challenges of conventional extraction are longer extraction time, requirement of costly and high purity solvent, evaporation of the huge amount of solvent, low extraction selectivity, and thermal decomposition of thermolabile compounds. To overcome these limitations of conventional extraction methods, new and promising extraction techniques are introduced. These techniques are referred as non-conventional extraction techniques. Therefore, in this review, some of the most promising techniques such as ultrasound-assisted extraction, pulsed electric field extraction, enzyme-assisted extraction, microwave-assisted extraction, pressurized liquid extraction, supercritical fluid extraction, pressurized low-polarity water extraction, and molecular distillation were discussed. The process systems along with industrial applications for non-conventional method of antioxidants extraction were discussed, and the comparative efficacies of different extraction methods were highlighted. Replacing conventional technologies by non-conventional ones for the extraction of valuable compounds from plant by-products processing industries has several advantages, which includes reduction of the processing time, energy consumption, and the uses of harmful and expensive solvents and increase in the extraction yields. Incorporation and development of hybrid methods should be investigated, while considering plant material characteristics and choice of compounds in future. Proper choice of standard methods also influences the measurement of extraction efficiency. The increasing economic significance of bioactive compounds and commodities rich in these bioactive compounds may lead to find out more sophisticated extraction methods in future.