Characterization of spray-dried tuna oil emulsified in two-layered interfacial membranes prepared using electrostatic layer-by-layer deposition

omega-3 Fatty acids have numerous health benefits, but their addition to foods is limited by oxidative rancidity. Spray-drying tuna oil-in-water emulsion droplets with a coating of lecithin and chitosan multilayer system could produce emulsion droplet interfacial membranes that are cationic and thick, both factors that can help control lipid oxidation. Physicochemical and oxidative stability of the spray-dried emulsions were determined as a function of storage temperature and relative humidity (RH). The combination of ethylenediaminetetraacetic acid (EDTA) and mixed tocopherols was able to increase the oxidative stability of dried emulsions. Lipid oxidation was more rapid during storage at low relative humidity (11% and 33% compared to 52% RH). At high moisture, physical modifications in the sample were observed, including reduced dispersibility and formation of brown pigments. Sugar crystallization or Maillard products produced at the higher humidities may have inhibited oxidation. Overall, spray-dried tuna oil-in-water emulsions stabilized by lecithin-chitosan membranes were more oxidatively stable than bulk oils and thus have excellent potential as an omega-3 fatty acid ingredient for functional foods.

Stability of spray-dried tuna oil emulsions encapsulated with two-layered interfacial membranes.

Omega-3 Fatty acids have numerous health benefits, but their addition to foods is limited by oxidative rancidity. Engineering the interfacial membrane of oil-in-water emulsion droplets to produce a cationic and/or thick interface is an effective method to control lipid oxidation. Cationic and thick emulsion droplet interfacial membranes can be produced by an electrostatic layer-by-layer deposition technique resulting in droplets that are coated by multiple layers of emulsifiers. Tuna oil-in-water emulsion droplets coated by lecithin and chitosan produce cationic emulsion droplets that are more oxidatively stable than emulsions coated by lecithin alone. Ethylenediaminetetraacetic acid (EDTA) was able to increase the oxidative stability of emulsions stabilized with lecithin and chitosan more effectively than mixed tocopherols. The combination of EDTA and mixed tocopherols was not more effective than EDTA alone suggesting that control of prooxidant metals was the most important antioxidant technology. The production of emulsion droplets coated with lecithin and chitosan could be an excellent technology for stabilization of oxidatively unstable lipids for use in a variety of food products.

Increasing the oxidative stability of liquid and dried tuna oil-in-water emulsions with electrostatic layer-by-layer deposition technology.

Protein binding to polymer brush, based on ion-exchange, hydrophobic, and affinity interactions.

Encapsulation of emulsified tuna oil in two-layered interfacial membranes prepared using electrostatic layer-by-layer deposition

Silver ions were loaded at a density of 1 mmol/g onto a sulfonic acid group-containing porous hollow-fiber membrane prepared by radiation-induced graft polymerization of an epoxy group-containing monomer with subsequent modification by reaction with sodium sulfite. The permeability (i.e., permeation flow rate per inside surface area of the hollow fiber) of 4.6% wt/vol bonito oil ethyl ester solution in water/ethanol (7.5:92.5, vol/vol) was 1.7 m/h at a permeation pressure of 0.1 MPa. Breakthrough curves (i.e., concentration changes of the effluent with increasing effluent volume) obtained with docosahexaenoic acid ethyl ester (DHA-Et) overlapped, irrespective of the permeation flow rate. This indicates that a higher rate of DHA-Et adsorption onto the silver ions on the membrane was attained with increasing permeation flow rate. DHA-Et, which was selectively bound to the membrane, was quantitatively eluted with acetonitrile as an eluent. The adsorption characteristics (i.e., binding rate, selectivity and durability for repeated use) of DHA-Et using the silver ion loaded porous hollow-fiber membrane were demonstrated. Feasibility studies will enable comparison of the purification cost of DHA-Et among the other purification techniques.

Isao Honjyo

Papers

Selective binding of docosahexaenoic acid ethyl ester to a silver-ion-loaded porous hollow-fiber membrane