Effect of olive mill waste extracts on the stability of oil-in-water emulsions

Abstract

In this research, the effectiveness of OMWE based emulsifiers on the production of stable oil-in-water emulsions was studied. The emulsifiers were all extracted at different pH (5, 7, and 9) but all samples were standardized to pH 7 for measurement with the utilization of Tris-base buffer solution (10mM). The O/W emulsion samples (10% w/w oil) were prepared according to the protocols and homogenized via an ultrasonic homogenizer. In order to study the capacity of the emulsifiers to ensure prolonged stability, the first batch was made with 1% w/w OMWE and then redone with 2% concentration. The effect of the emulsifier concentration was then analyzed by measuring the electric charge, the rheology and droplet size. The batch prepared with 1% emulsifier showed weak results in general, but showed that there was potential for the utilization in the food industry. The electrical charge was between 0 and -11mV, while the sample viscosity ranged from 10 to 90 Pa. s. The droplet size seemed to revolve around 1.350 and 1.170μm on average. Phase separation became apparent shortly after the preparation of the samples, while aggregates started to form and creaming was visible after approximately 8h. The second batch, however proved this assumption as the results showed a tremendous improvement. Most importantly, the average droplet size dropped drastically, from values above 1 to values 0.62-0.59 μm. This showed the team that a small increase in OMWE concentration was enough to provide more stable emulsions and that these wastes showed great potential after all for future use. Out of the three extraction pH for the emulsifiers, the one that was extracted at pH 5 showed the most promising results, since it had good electrical charge between the molecules and great viscosity, both important factors for emulsion stability. It is important to note here that more research needs to be done on more parameters on the level of effect that OMWE emulsifiers have on emulsion stability. Creating a prolonged stable emulsion made by olive mill waste could pave the way for a cleaner more sustainable food industry.