Integrated drying-extraction workflow for the revalorization of avocado peel

Alejandro Rojas-García, Abigail García‐Villegas, Antonio Segura-Carretero, David Arraéz-Román, María de la Luz Cádiz‐Gurrea

The revalorization of avocado peel (AP) has two main benefits: reducing agrifood waste while recovering extracts rich in phenolic compounds with industrial and nutraceutical applications. In this study, drying and extraction were optimized as an integrated process rather than independent operations. Three drying strategies — far-infrared radiation (FIR), for the first time applied to AP, conveyor-belt drying (CBD), and passive convective drying (PCI) — were evaluated in terms of drying kinetics, phenolic preservation, and energy demand. Based on preliminary tests, selected drying conditions led to ultrasound-assisted extraction (UAE) optimization through response surface methodology (RSM), where ethanol concentration significantly influenced all matrices. Once optimized, AP extracts (API, APA, and APE) exhibited complementary bioactive profiles: whereas APE showed the highest phenolic content (285 ± 3 mg GAE/g DW) and ferric reducing antioxidant power (2.46 ± 0.03 mmol Fe 2+ /g DW), APA stood out at flavonoid content (245 ± 3 mg EE/g DW) and xanthine oxidase inhibition (IC 50 = 1.4 ± 0.7 mg/L), and API at acetylcholinesterase inhibition (IC 50 = 34 ± 5 mg/L) as well, with no single extract outperforming the others across all evaluated parameters. Multivariate analysis confirmed that drying-induced structural modifications strongly conditioned extraction efficiency and bioactivity, highlighting the need for matrix-dependent optimization. Industrially, while CBD was competitive only at high load factors (50 ± 10 kWh/kg FW), FIR offered the best flexibility and energy efficiency (11 ± 3 kWh/kg FW). Overall, this work demonstrated the potential of coupled drying-extraction strategies for avocado peel revalorization, providing a basis for further scalable applications.