Loading olive mill wastewater polyphenols in microparticles via spray drying

Italy Introduction: Olive mill wastewater (OMW), derived from olive oil production, has the potential to be transformed, thanks to various handling protocols, from a waste product with environmental concerns into a wealthy product. In fact, OMW is rich in polyphenols and other natural antioxidants, which play a vital role in human health through the regulation of metabolism, chronic disease and cell proliferation (1). The conversion of OMW into a free-flowing solid powdered form, with maintained antioxidant properties, represents, therefore, a challenging target, with great potential for the development of pharmaceutical, nutraceutical, and cosmetic products, in the perspective of a circular economy approach. Methods: Maltodextrin low (MDLMW) and high (MDLMW) molecular weight and colloidal silicon dioxide (Aerosil® 300F), chosen as model carrier materials, were dispersed in different weight ratios (Table 1) in 50 mL of OMW, suitably treated through filtration and reverse osmosis (solid content in treated OMW 2.045 ± 0.130 %, n=3). To obtain high process yields, dispersions were spray-dried (Mini-Spray-drier, Buchi) using the following conditions: inlet temperature 150 °C, aspirator 100%, atomizing airflow 600 L/h, feed pump 10%. Particle size was measured by laser diffraction analysis (Mastersizer® 3000E, Malvern) and morphology was assessed by scanning electron microscopy (Mira3 XMU, Tescan). The antioxidant activity of powders and native OMW (Control) was measured (2) and expressed as DPPH%; the total polyphenol content (TPs) was also determined (3) and expressed as Gallic Acid Equivalents (GAE). . Results: All spray-dried powders were monodisperse in particle size distribution, with mean diameter (D[4,3]) values ranging from 6.47 to 9.05 µm. SEM images showed that all powders were composed by round-shaped microparticles. The spray drying process did not affect DPPH radical scavenger activity nor TPs content of powders in comparison with native OMW. In fact, no significant difference (One-Way Anova, p>0.05) of the DPPH% or GAE values was observed between S1-S4 powders and unprocessed OMW (Figure 1). Conclusion: This work proves the feasibility of spray drying OMW to obtain a micronized powder loaded with polyphenols and other natural antioxidants, that could be profitably employed as a loose powder for wound treatment or intended for nutraceutical purposes, once loaded in capsules to be orally administered. Spray drying represents, therefore, a powerful tool to obtain from a waste product an added value material with a potential for biomedical use. Further studies are in progress to cross-link microparticle wall material, in order to achieve a controlled release of the active ingredients. Acknowledgements: This work was financially supported by the University of Pavia (Fondo Ricerca Giovani 2019 and Cicops scholarship to Dr. A. J. Paredes). References: (1) Fraga CG, Croft KD, Kennedy DO, Tomás-Barberán F A. Food Funct. 2019:10, 514–528. (2) Mielnik M.B, Olsen E, Vogt G, Adeline D, Skrede G. LWT - Food Sci. Technol. 2006: 39, 191-198. (3) Singleton V L, Rossi J A. Am. J. Enol. Vitic. 1965: 16, 117 – 128.