Evaluation of the Physical and Oxidative Stabilities of Fish Oil-in-Water-in-Olive Oil Double Emulsions (O1/W/O2) Stabilized with Whey Protein Hydrolysate

This work studied the physical and oxidative stabilities of fish oil-in-water-in-olive oil double emulsions (O-1/W/O-2), where whey protein hydrolysate was used as a hydrophilic emulsifier. A 20 wt.% fish oil-in-water emulsion, stabilized with whey protein hydrolysate (oil: protein ratio of 5:2 w/w) and with a zeta potential of similar to-40 mV, only slightly increased its D-4,D-3 value during storage at 8 degrees C for seven days (from 0.725 to 0.897 mu m), although it showed severe physical destabilization when stored at 25 degrees C for seven days (D-4,D-3 value increased from 0.706 to 9.035 mu m). The oxidative stability of the 20 wt.% fish oil-in-water emulsion decreased when the storage temperature increased (25 vs. 8 degrees C) as indicated by peroxide and p-anisidine values, both in the presence or not of prooxidants (Fe2+). Confocal microscopy images confirmed the formation of 20 wt.% fish oil-in-water-in-olive oil (ratio 25:75 w/w) using Polyglycerol polyricinoleate (PGPR, 4 wt.%). Double emulsions were fairly physically stable for 7 days (both at 25 and 8 degrees C) (Turbiscan stability index, TSI < 4). Moreover, double emulsions had low peroxide (< 7 meq O-2/kg oil) and p-anisidine (< 7) values that did not increase during storage independently of the storage temperature (8 or 25 degrees C) and the presence or not of prooxidants (Fe2+), which denotes oxidative stability.

Automated summary

This work investigated the physical and oxidative stabilities of fish oil-in-water-in-olive oil double emulsions using whey protein hydrolysate as a hydrophilic emulsifier. The results showed that a 20 wt.% fish oil-in-water emulsion had good physical stability at low temperature but underwent severe physical destabilization at high temperature. The oxidative stability experiment indicated that the fish oil-in-water emulsion had faster oxidation reaction at high temperature. In contrast, the double emulsions with the addition of olive oil exhibited good physical and oxidative stability under all conditions.