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

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.

Automated summary

This study extracted phenolic compounds from hexane-defatted Arbequina olive pomace using acidified methanolic-water gradients and evaluated their antioxidant and antimicrobial activities. The results showed that the total phenolic contents increased with the increase of methanol percentage, but the polar phenolic compounds decreased while less-polar phenolic compounds increased. The water fractions exhibited higher in vitro antioxidant and antimicrobial activities compared to the higher methanolic fractions. This study provides data foundations for the practical valorization and industrial food applications of olive pomace extracts.