Bioactive compounds from by-products of eggplant: functional properties, potential applications and advances in valorization methods

Abstract

Background: Eggplant (also known as aubergine) by-products, which consist mostly of peel and calyx, are generated in substantial amounts by industrial food processing sections and usually discarded as waste without further utilization. However, studies have demonstrated that these by-products are superb sources of bioactive compounds. Therefore, the disposal of eggplant by-products not only gives rise to environmental and economic consequences but also represents a tremendous loss of valuable materials.

Scope and approach: This review is aimed to assess the potentials of eggplant by-products as a source of bioactive compounds by evaluating the functional properties and production approaches of the bioactives and exploring their applications in food and pharmaceutical industries.

Key findings and conclusions: It is estimated that over ten million tonnes of eggplant by-products are generated annually. The peel is an outstanding source of delphinidin-derived anthocyanins with remarkable antioxidant, antimicrobial and anticancer properties. Moreover, both peel and calyx are high-yielding sources of pectin with excellent functional properties. Several methods, from conventional approaches to ultrasound and microwave-assisted techniques, have been developed and optimized for extraction of anthocyanins and pectin. Furthermore, integrated valorization of eggplant by-products, which consists of simultaneous extraction of phenolics and pectin followed by production of pullulan from the leftovers, has shown promising results. It is also demonstrated that eggplant peel anthocyanins are potent alternatives to synthetic additives for fortification and shelf-life improvement of food products. However, further studies are required in regards to the integrated valorization technique, health-promoting properties and food and pharmaceutical applications of these bioactive compounds.