Ph.D. Dissertation:

Use of nanocomplexes of whey protein concentrate and Arabic gum as carrier of fish oil in probiotic low fat fermented milk

Fish oil consists of omega-3 fatty acids which play an important role in retaining cardiovascular system health. Its susceptibility to oxidation causes it to be considerably degraded during the processing and storage of food products. Therefore, encapsulation of this ingredient through freeze drying was studied with the aim of protecting it against environmental conditions. Gum Arabic (GA) and whey protein concentrate (WPC) were used at various ratios as the wall material for fish oil nanoencapsulation and Tween 80 was applied as the emulsifier. To that end, a water in oil (W/O) emulsion was prepared by sonication, containing 6% fish oil dispersed in an aqueous solution including 20 and 25% total wall material. The emulsion was sonicated at 24kHz for 120 s. The emulsion droplet sizes were measured using a particle size analyzer. The emulsion was then freeze dried and the nanocapsules were incorporated into fermented milk and their effects were examined on the milk. Results showed that the type and concentration of the compounds employed as wall material were effective on the nanocapsule properties. The smallest droplet size (50 nm) and the highest encapsulation efficiency belonged to the emulsion containing 100% GA. Moreover, the lowest surface oil content and pH, and the highest zeta potential and moisture content were related to the same emulsion. The encapsulation effect decreased during storage. In addition, the smallest effect of encapsulation on total acceptance, taste, aroma, texture and the content of EPA and DHA was observed in the samples encapsulated with 20% total wall material (GA) and 2% emulsifier. On the other hand, the biggest effect of encapsulation on Lactobacillus viability, total acceptance and EPA and DHA contents pertained to the fish oil encapsulated with 25% total wall material( GA) and 4% emulsifier.

Keywords: Fish oil, Nanoencapsulation, sensory evaluation, fermented milk,viability probiotic bacteria .