Membrane technology for the separation and the clarification of food additives recovered from olive mill wastewater

In our earlier studies, we proposed a method for the simultaneous recovery of dietary fibers and phenols from olive mill wastewater (OMW) in two different streams: (i) an alcohol insoluble residue (AIR) rich in dietary fibers and (ii) an ethanolic liquid rich in phenols. The ethanolic liquid has been proposed for a direct application in the beverage industry, i.e. as an additive to produce soft drinks. Moreover, the water soluble fraction of the AIR has been proposed as fat replacer in meatballs. The objective of the current study was to investigate the separation of two high added-value products (pectin containing solution and phenol containing beverage) recovered from the aforementioned streams by using membrane technology like ultrafiltration (UF) and nanofiltration (NF). For this purpose, both liquids were processed with four types of UF (100, 25, 10 and 2 kDa) and one NF membranes under optimum transmembrane (TMP) pressure. Retention coefficients and performance parameters were monitored for each experiment. With regard to the pectin containing solution, the membranes possessing molecular weight cut-off (MWCO) between 25 and 100 kDa were able to quantitatively recover pectin in the concentrate stream and separate it from smaller solutes like K, Na and phenols. The clarified pectin material could be utilized as gelling agent after concentration in low fat meatballs. With regard to the phenol containing beverage, the membrane of 25 kDa MWCO was able to partially remove the heavier fragments of hydroxycinnamic acid derivatives and flavonols in the concentrate stream and at the same time to sustain the antioxidant properties of the beverage in the permeate stream. Finally, NF could be used in order to clarify the beverage from the K and Na, but this process would reduce the antioxidant ability of the product due to a loss of ο-diphenols in the permeate.