Monitoring the moisture reduction and status of bioactive compounds in extra-virgin olive oil over the industrial filtration process

The aim of this study was to evaluate extra-virgin olive oil (EVOO) moisture and phenolic compounds content during industrial filtration, which is widely applied in the most olive-oil industries of the main producing countries of the Mediterranean as a final step prior to selling the oil. For this purpose, conventional filtration process was performed in duplicate using two lots (lot 1 and lot 2), for a total amount of 45,000 kg of EVOO each. The EVOOs were from the main Spanish olive varieties (Hojiblanca, Manzanilla, Picual, and Arbequina). Cloudy EVOOs were filtered using Vitacel® L-90 and Filtracel® EFC-950 as filter aids together with filtration tank. The moisture content was determined in unfiltered and filtered EVOOs. In addition, the individual phenolic compounds were qualitatively and quantitatively characterized by HPLC–ESI-TOF/MS. The results clearly showed that filtration sharply decreased moisture. Nevertheless, the time course of phenolic compounds during filtration differed for each family. Whereas phenolic alcohols and flavones decreased during filtration, secoiridoids tended to increase, while lignans were the least affected group. Although filtration can make EVOO brilliant and can increase its shelf life by reducing its moisture content, filtration sacrifices certain phenolic compounds which could affect EVOO oxidative stability and its nutritional quality. Consequently, to maintain olive-oil quality, producers need to take into account both moisture loss as well as the antioxidant content during EVOO filtration.