Pectin Recovery Based on the Exploitation of Kiwi By-Products and the Application of Green Extraction Techniques ^†

The Actinidia genus comprises 54 species and 21 varieties of which A. chinensis var. chinensis and A. chinensis var. deliciosa are the most commercialized ones. The nutritional properties of kiwifruit have prompted their global production to nearly reach the value of 4.5 million tons per year, with Asia being one of the top producers. This increment in their production has raised a parallel augment of associated organic wastes, especially when kiwifruits are used for processed products. The most abundant by-products obtained include skins, seeds and discarded fruits. This biomass has a huge potential for its high content of bioactive compounds, such as dietary fiber or polyphenols. Therefore, it has been targeted by the food industry as a sustainable and cost-effective source of natural ingredients, highly demanded by consumers. Indeed, kiwi skins and seeds have been pointed out as a relevant source of pectin followed by the kiwi pulp. Pectin is a recognized ingredient due to the organoleptic properties it may confer but also for its prebiotic capacities. The recovery of pectin has been mainly performed via the application of extraction techniques that implied the use of chemical reagents such as acids. Nowadays, the use of chemicals is negatively regarded for their associated side effects. Indeed, customers’ claims for chemical-free food ingredients have triggered the development and application of green extraction techniques: ultrasonic, microwave, enzyme, supercritical fluid or electrical pulse. Pectin has been successfully extracted with these green techniques both in terms of yield and quality, improving results obtained with traditional extraction techniques. Therefore, the main objective of this work is to review the wide variability of green techniques applied to extract pectin along with the comparison of the optimal parameters as a basis for the future development of an optimized extraction method. In addition, this work also aims to disclose the potential of kiwifruit by-products as a source of pectin and their industrial applications for the development of functional foods, nutraceuticals, food additives or cosmetics.