Recovery and stability over time of phenolic fractions by an industrial filtration system of olive mill waste waters: a three years study

BACKGROUND: The recovery of phenolic compounds from olivemilling is recognized as strategic for producers. The aim of this work was to evaluate the quality and stability of retentates obtained from olive mill wastewaters treated with a membrane filtration system constituted by amicro-, ultra- and nanofiltration, followed by a final reverse osmosis, over three crop seasons. Efficiencywas evaluated in terms of phenolic amount in the retentates and of organic load in the final discardedwaters. Phenolic compounds were quantified using tyrosol as external standard. RESULTS: Our study highlighted a reproducibility of the process over years and a low organic load in permeates from reverse osmosis. Hydroxytyrosol was very stable in the liquid products at 18–28 ∘C over 24months of storage. The retentates from reverse osmosis showed the highest phenolic content (78.6mg g−1 dry matter in 2015), associated with a potassium content of 22 g kg−1. CONCLUSIONS: The liquid concentrated retentates showed an unexpected stability over time of their bioactive phenolic compounds, particularly of hydroxytyrosol. These samples recovered fromolivemillwastewaters can be good sources of natural antioxidants and potassium to guarantee the correct intake and to formulate new food ingredients or food products. © 2017 Society of Chemical Industry