Flash vacuum expansion assisted valorization of coffee pulp waste: thermodynamic and sorption modeling of phenolic‐rich spray‐dried extracts

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Abstract BACKGROUND Flash vacuum expansion (FVE) was applied as a pretreatment to improve the recovery of total phenolic compounds (TPC) from coffee pulp waste. After determining the optimal treatment, the phenolic‐enriched extract was stabilized by spray‐drying microencapsulation. Adsorption isotherms of the resulting powders (MCE‐SD) were determined at three temperatures and fitted to seven mathematical models to estimate enthalpy and entropy using the Othmer equation. Storage experiments at 35 °C under different water activity ( a w ) levels were conducted to monitor TPC, color, and microstructural stability by scanning electron microscopy (SEM). RESULTS Flash vacuum expansion‐treated samples showed a significant ( P < 0.05) TPC increase of up to 27.29% compared with the control, mainly due to turgor loss and vacuolar rupture in the pulp. Isotherms exhibited a type II shape, with the Guggenheim–Anderson–de Boer (GAB) model providing the best fit, followed by the Brunauer–Emmett–Teller (BET), White and Eiring, and Adam and Shove models. The highest enthalpy corresponded to the monolayer region and minimum entropy zone, where water molecules were more ordered. Samples stored within the minimum entropy zone ( a w = 0.24–0.39 at 35 °C) showed minimal TPC degradation (0.62% to 1.45%) and low color variation ( ΔE = 0.52–3.39), whereas higher a w levels led to greater TPC losses (21.11% to 38.31%), larger color changes ( ΔE = 11.14–50.78), and matrix collapse. CONCLUSION Flash vacuum expansion coupled with spray drying represents a sustainable strategy for coffee pulp valorization through the production of phenolic‐rich microcapsules. Sorption modeling and thermodynamic analysis enabled the identification of storage conditions associated with maximum phenolic stability, color preservation, and microstructural integrity. © 2026 Society of Chemical Industry.

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