An overview of the traditional and innovative approaches for pectin extraction from plant food wastes and by-products: Ultrasound-, microwaves-, and enzyme-assisted extraction

A large amount of food wastes and by-products are produced from farm to plate. They represent valuable sources for the production of high-added value compounds such as pectin. Pectin is the methylated ester of polygalacturonic acid and presents a wide range of applications in pharmaceutical and cosmetic products as well as in food industry such as gelling agent in fruit-based products, stabilizer in fruit and milk beverages and fruit filling for bakery and confectionary products, among others. Therefore, pectin recovery is of great importance. The commercially available pectin is almost exclusively derived from citrus peels or apple pomace, by-products from fruit juice manufacturing. But, nowadays the number of novel food waste and by-products sources for pectin extraction are increasing. Moreover, the application of innovative approaches is necessary due to the limitation of conventional processes. The present review will focus on the conventional and innovative processing techniques (microwave extraction, enzymatic extraction, ultrasound-assisted extraction) to extract pectin from different wastes and by-products. The pectin extraction differs according to the matrix studied as well as temperature, pH, time, solvents, and solid to liquid ratio. The use of innovative extraction processes such as ultrasound, microwave and enzymes can be a useful tool to increase pectin yield and quality, and reducing extraction time, temperature, use of toxic solvents and strong acidic conditions for pectin recovery. Moreover, the combination of solvent modelling and the use of particular extraction processes can enable the selective recovery of pectin.