1 Membrane technology for the separation and the clarification of food additives recovered from olive mill wastewater Charis M. Galanakis a , Eva Tornberg b , Vassilis Gekas* c a Department of Environmental Engineering, Technical University of Crete, Chania, Greece, email: cgalanakis@isc.tuc.gr b Department of Food Technology, Engineering and Nutrition, Faculty of Engineering, Lund University, Lund, Sweden, e-mail: eva.tornberg@food.lth.se c Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Lemesos, Cyprus, e-mail: vassilis.gekas@cut.ac.cy ABSTRACT 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. Keywords: Membrane, Ultrafiltration, Nanofiltration, Pectin, Phenols INTRODUCTION Olive is known to contain an appreciable amount of phenols with good antioxidant properties and dietary fibers with promising water holding capacity. However, the majority of these compounds are lost in OMW during olive oil production. For example, OMW typically contains 98% of the total phenols in the olive fruit. OMW has also been referred to possess soluble dietary fibers and especially pectin material with satisfying gelling ability [1]. In our earlier studies, we recovered dietary fibers from OMW, based on the thermal extraction, prior the precipitation of macromolecules with 85 mL ethanol/100 mL [2, 3]. The developed method proposed the simultaneous recovery of dietary fibers and phenols in two different streams: (i) an alcohol insoluble residue 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 [4]. Moreover, the water soluble fraction of the alcohol insoluble residue (WSAIR) has been proposed as fat replacer in meatballs achieved by dissolving the alcohol insoluble residue in water and sequentially separating it from the corresponding water insoluble fraction [5]. Despite the promising applications, these rather crude materials should be further clarified or separated before utilization in order to optimize their functional properties and improve their taste. The objective of the current study is to investigate the clarification and the recovery of high added value ingredients like pectin and phenols from the aqueous solutions derived by the aforementioned WSAIR material and the ethanolic extract, respectively. For this purpose, both materials were processed with different UF and NF membranes under constant conditions, i.e. temperature and circulation flux. Parameters like permeate flux and retention coefficients of several components were monitored for each feed-membrane combination.