Characterization of California olive pomace fractions and their in vitro antioxidant and antimicrobial activities

Authors: ZHAO, HEFEI - University Of California, Davis; KIM, YOONBIN - University Of California, Davis; Avena-Bustillos, Roberto; NITIN, NITIN - University Of California, Davis; WANG, SELINA - University Of California, Davis

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2023
Publication Date: 3/23/2023
Citation: Zhao, H., Kim, Y., Avena Bustillos, R.D., Nitin, N., Wang, S.C. 2023. Characterization of California olive pomace fractions and their in vitro antioxidant and antimicrobial activities. LWT - Food Science and Technology. 180. Article 114677. https://doi.org/10.1016/j.lwt.2023.114677.
DOI: https://doi.org/10.1016/j.lwt.2023.114677

Interpretive Summary: Approximately 80% of fresh olives are used to produce olive oil. Olive pomace, the major byproduct of olive oil extraction, contains phenolic compounds with significant antioxidant and antimicrobial properties. Here we investigated the effect of different solvent preparations used in the extraction process on the subsequent antioxidant and antimicrobial activities of the phenolic compounds in the pomace of California Arbequina olives. Specifically, water extracts of the olive pomace were processed using increasing methanol concentrations by a process called preparative C18 chromatography. The preparative operation parameters of C18 would be directly used to scale-up separation processes; however, further studies for operational parameters are needed.

Technical Abstract: Olive oil production yields a massive amount of byproduct, olive pomace (OP). Hexane-defatted Arbequina olive pomace from California, United States, was extracted with water and loaded to a preparative C18 chromatography. Phenolic desorption was applied by acidified methanolic-water gradients. Phenolic compound profiles and antioxidant/antimicrobial activities were determined. Results showed that the total phenolic contents of the fractions increased with the increase of the percentage of methanol in water gradients; however, the polar phenolic compound profiles generally decreased, while less-polar phenolic compound profiles increased. Oleuropein-aglycone-di-aldehyde (3,4-DHPEA-EDA) detected in water extract was not found in the acidified 35 mL/100 mL and acidified 70 mL/100 mL methanol fractions, but there was a new peak tentatively assigned as 3,4-DHPEA-EDA dimer. The in vitro antioxidant activities of water fractions were higher than that of higher methanolic fractions when they were compared at the same level of gallic acid equivalents; the same trend was observed for the antimicrobial activities evaluated using non-Shiga toxin-producing Escherichia coli O157:H7 and Listeria innocua. This study provides knowledge as data foundations for the practical valorization and industrial food applications of olive pomace extracts.