Cleaning protocols for organic microfiltration membranes used in premix membrane emulsification

Premix membrane emulsification (ME) has been used to produce mono-disperse emulsions under process conditions that reduce the mechanical stress of sensitive compounds such as proteins, which can increase the stability of encapsulated biocompounds, but can cause membrane fouling. An organic nylon microfiltration membrane used to produce stable oil/water (O/W) emulsions stabilized with whey protein has been cleaned with different concentrations of commercial cleaning agents (Derquim+, Tween 20, or sodium hydroxide) alone or in combination, under different operation modes, including circulating the agent in forward or backwash mode. The efficiency of the membrane cleaning process was assessed using water flux recovery, membrane surface characterization by attenuated total reflectance infrared microspectroscopy (ATR-IRMS) and by assessing the performance of the cleaned membrane in premix ME. The results show that the highest level of cleaning efficiency was obtained with Derquim+ circulating in backwash mode, followed by a combination of Derquim+ and NaOH at 50 °C. It was found that regardless of the cleaning agent used, an increase in the concentration of the agent had a lesser effect on increasing water flux recovery than increasing backwash pressure. Nevertheless, the water flux recovery values obtained with the cleaning agents tested indicate that some foulants (oil and/or whey protein) were left on the membrane surface and inside the pores. It was found that the membranes could be reused in premix ME to produce whey protein stabilized O/W emulsions, but the fluxes obtained during the second emulsification were always lower than those obtained using a new membrane, although the droplet size diameter of the emulsions obtained with a cleaned membrane was similar to the one obtained with a new membrane, except for membranes cleaned with a combination of surfactant and NaOH. ATR-IRMS analysis confirmed that membranes cleaned using Tween 20 had some foulants, primarily oil, left on the surface. This study shows the feasibility of applying membrane cleaning to organic membranes employed in premix ME and the viability of reusing such membranes for emulsification purposes.

► Cleaning and reusing of nylon membranes to produce O/W protein stabilized emulsions. ► Physico-chemical cleaning did not completely restore pure water flux. ► Emulsification with cleaned membranes did not affect droplet size, only fluxes. ► ATR-MS showed oil remaining on the membrane surface after cleaning.