Strategies for bioactive compound recovery from grape and apple wastes: traditional and emerging technologies to reach zero waste discharge

Abstract

The presence of numerous bioactive compounds in fruit wastes indicates the potential to use them as low-cost resourcefor generating value-added ingredients. The integral use of residual biomass from wine and cider industries was proposed.Phenolic-rich liquid extracts were produced from grape marc (GM), grape stalk (GS), and apple pomace (AP) by applyinghydrothermal (T), ultrasound-assisted (US), and enzymatic (EZ) extractions, and the remaining solid fraction (RSF) wasthen converted into fber concentrated powders by air-drying. Additionally, the direct conversion of the whole initialwastes into integral powders rich in both fber and phenolic compounds was proposed. An integral physicochemical studywas performed: phenolic compounds, content and techno-functional properties of dietary fber, and physical and stabilityproperties. The T extraction conducted for 75 min at 75 °C demonstrated superior efcacy in terms of total polyphenolcontent (TPC) and antioxidant capacity (AC). Under these optimal conditions, the extracts exhibited a TPC content of251±2 mg GAE/100 g from GM, 1420±5 mg GAE/100 g from GS, and 23±2 mg GAE/100 g from AP. GS extractwas mainly composed of procyanidins, catechin, and epicatechin, while in AP, favonols (mainly rutin) represented themajority group. The GM extract showed a richer polyphenol profle including condensed tannins, favonols (mainly rutin),favan-3-ols (catechin), and a greater variety of phenolic acids. Within the fber-rich powders produced from the RSF(optimal extraction conditions), those from grape wastes registered higher remaining TPC and total dietary fber content(47–51%), mainly composed of insoluble fber (IDF). AP powders (integral and from RSF) showed a higher soluble fbercontent (SDF), a more balanced IDF/SDF ratio (1.9 and 3.3, respectively), and better hydration properties. Among theintegral powders, GM and GS showed high level of TPC (997–1600 mg GAE/100 g), and suitable techno-functionalproperties. Physical properties are suggestive of free-fowing stable powdered ingredients in all cases. The fndings ofer asubstantial advance in waste valorization, benefting not only scientists, but also wine and cider producers, as well as thefood industry. They pave the way for converting various fruit wastes into diverse food ingredients. This approach enablesthe economic value recovery while delivering substantial environmental benefts, achieving a zero waste state. Employingthese ingredients in creating new functional foods could enhance public health.