Pectins obtained by ultrasound from agroindustrial by-products

Agroindustrial wastes and by-products from crops can be used for the extraction of valuable components such as pectins, contributing to sustainability and environmental protection. Pectins are complex polysaccharides of the plant cell-walls where fulfill important biological functions, showing high hydration capacity, swelling, thickening, and gelling effects. These features are also of technological interest to the food and pharmaceutical industries. Pectin extraction by conventional techniques involves high-temperature stages and the use of mineral acids which cause deteriorating reactions, loss of functionality, and decreased yield. The acidic and/or alkaline waste streams generated produce environmental pollution and additional costs for effluent treatments. Ultrasound-assisted extraction of pectin allows using less solvent and reduces the environmental impact in terms of energy and time. The present paper reviews some selected bibliography published in the last years concerning the pectin isolation from agroindustrial by-products by means of ultrasound-assisted techniques. A brief revision about pectin structure including the latest results published in relation to interactions with other cell-wall polymers is presented to understand to what extent pectins are modified by the extractive conditions used. The incidence of ultrasound on the yield, chemical structure, molecular weight, and functional properties is discussed concluding that more systematic studies that consider not only the yield but also the process conditions, the chemical composition of the extractant, the chemical structure and functionality of the product, are necessary to have a solid database for process optimization. Moreover, ultrasound combined with other non-conventional techniques can help achieve an efficient extraction, minimizing non-desired changes. • Ultrasound (US) facilitates the release of pectin from agroindustrial residues. • US combined with acids, enzymes, microwaves reduces pectin extraction times. • Pectin functionality is affected by US due to the changes caused by cavitation. • The chemical structure of extracted pectin is affected by US treatment. • US combined with other techniques can help minimize unwanted changes in pectins.