Powdered ingredients from olive pomace: Impact of drying temperature and defatting on bioactive potential

Despite the well-documented generation of solid residue in olive mills, the pomace matrix remains a rich source of entrapped polyphenols. This study aimed to valorize olive pomace (Neuquén, Argentina) by producing functional powders, evaluating the impact of drying and defatting on polyphenol retention and antioxidant capacity.

Pomace was air-dried (10% relative humidity, 1,5 m/s air velocity) at different air temperatures (60, 70, and 80°C). Drying curves were describes using Page, Logarithmic, and Henderson & Pabis semiempirical models. Dried pomaces were ground, sieved (30-mesh), and analyzed for total polyphenol content (TPC, Folin-Ciocalteu) and antioxidant activity (DPPH, ABTS, FRAP). Air-dried samples were then compared with those subjected to freeze-drying, used as a reference process in terms of bioactive preservation. The effect of defatting on phenolic recovery was also evaluated.

The Page model provided the best fit for the drying curves at all temperatures, resulting in an optimal drying time of 180 min and ensuring the stability of the pomace (aw < 0.3). Drying at 80°C resulted in significantly higher TPC values (532.46 ± 37.59 mg/100g d.b.) than drying at 60 °C (329.98 ± 43.48 mg/100g d.b.), consistent with the trend observed for antioxidant capacity (i.e, 205 ± 27 mg/100g d.b at 60°C vs 301 ± 50 mg/100g d.b at 80°C by the DPPH method). Based on these results, defatting was evaluated exclusively in samples dried at 80°C, slightly increasing TPC recovery to 584.60 ± 3.31 mg/100g d.b. Freeze-drying enhanced polyphenol retention in both non-defatted powders (785.73 ± 49.77 mg/100g d.b.), and defatted ones (1,058.93 ± 21.74 mg/100g d.b.).

Convective drying at 80°C for 180 min provides an efficient and scalable strategy for manufacturing bioactive olive pomace powders. Sequential defatting optimizes phenolic recovery and antioxidant potential, supporting the sustainable industrial valorization of olive oil by-products as functional food ingredients.