**3. Membrane technology**

Membrane technology is becoming increasingly important as a green processing and separation method in food processing and waste water treatment Membranes are used as filters in separation processes and have a wide variety of applications Membrane technology is now competitive compared to conventional techniques such as adsorption, ion exchangers and sand filters.

The main advantage of membrane processing is that it avoids the use of any chemicals that have to be discharged. It works with relatively high efficiency and low energy consumption (Mulder, 1996). It also has the advantage of operating at ambient temperature, resulting in preservation of heat-sensitive components and nutritional value of food products (Dewettinck & Le, 2011).

Membrane separation processes differ greatly in the type of membranes and driving forces used for separation, the process design, and the area of application. There are many different membrane processes, including reverse osmosis, micro-, ultra- and nanofiltration, dialysis, electrodialysis, Donnan dialysis, pervaporation, gas seperation, membrane contactors, membrane distillation, membrane based solvent extraction, membrane reactors, etc. Among them, the innovative methods preferred by the food industry are pressure driven separation processes such as reverse osmosis, nanofiltration, ultrafiltration and microfiltration. These preferred methods facilitate the separation of components with a large range of particle sizes. The obtained products are generally of high quality and less posttreatment procedures are required (Baker, 2004).

Potential Applications of Green Technologies in Olive Oil Industry 299

In another study, OMW was used to investigate the variation of COD and total organic carbon (TOC) removal efficiencies together with permeate fluxes for ultrafiltration process (Akdemir & Ozer, 2009). Two types of ultrafiltration membranes which are JW (polyvinylidinedifluoride) and MW (ultrafilic) gave close removal efficiencies. Ultrafiltration membranes with bigger molecular weight cut-offs for OMW were suggested to increase flux value and decrease efficiency loss. In their previous work, observed COD removal efciency by ultraltration without pretreatment was found higher than 80% by promising value for OMW (Akdemir & Ozer, 2008). El-Abbassi et al. (2009) studied the treatment of OMW to obtain high value-added compounds such as sugar and polyphenols, by membrane distillation. Two types of commercial membranes, polytetrafluoroethylene (TF200) and polyvinilydene fluoride (GVHP), were compared and the effects of membrane parameters on direct contact membrane distillation (DCMD) performance (i.e. permeate flux and polyphenols retention) were investigated. Their results demonstrated that TF200 had a better separation coefficient (99%) after 9 h of DCMD operation than that of GVHP (89%). OMW concentration factor was found

Another OWM treatment was tested by Dhaouadi and Marrot (2008). Diluted solutions of OMW were treated in a ceramic membrane bioreactor with biomass specially acclimated to phenol. It gave stabilized permeate flux with zero suspended solid and no phenolic compounds. No fouling problems occurred during the experiments. OMW treatment in a membrane bioreactor can be used as a pre-treatment stage for the removal of phenolic

Recently, Coskun et al. (2010) studied the treatment of OWM using nanofiltration and reverse osmosis membranes. They reported that overall COD removal efficiencies were 97.5%. It was shown that reverse osmosis membranes are capable of producing a higher quality effluent from OMW than nanofiltration membranes. NF270 membranes were found to be most applicable among nanofiltration membranes due to their higher fluxes and higher removal efficiencies. In addition, it was found that centrifugation alone can be used

In summary, there appears to be a potential for the use of membrane technology in the olive oil industry. Membranes can provide an opportunity to develop alternative environmentally friendly processes for the refining of olive oils and treatment of OWM. Despite promising results, further studies must be done on this new approach, namely, to evaluate the effect of the process on the oil composition, to improve flow rate, to reduce fouling inclusions and to

Lipids require modification in order to be used for special purposes or production of value added products. Lipids can be modified by hydrogenation, blending, fractionation and chemical or enzymatic reactions such as hydrolysis, direct esterification and interesterification.

Interesterification reactions are widely studied to produce margarines and shortenings with zero-*trans* fatty acids, cocoa butter equivalents, structured lipids with specific nutritional properties, partial glycerides and biodiesel. Chemical interesterification uses metal

as a promising option for primary treatment of OMWs with nanofiltration process.

to be 1.72 for TF200, whereas it was only 1.4 for GVHP after 9 h.

compounds before a conventional biological process.

assess economic viability.

**4.1 Enzymatic conversions** 

**4. Bioconversions** 
