No abstract

Emulsions were prepared with 5% (w/v) solutions of sodium caseinate (Na Cas) and soy oil at oil/protein ratios of 0.25-3.0 by homogenization at 10--50 MPa. Emulsions were spray-dried to yield powders with 20--75% oil (w/w). Emulsion oil droplet size and interfacial protein load were determined. Microencapsulation efficiency (ME), redispersion properties, and structure of the powders were analyzed. The size of emulsion oil droplets decreased with increasing homogenization pressure but was not influenced by oil/protein ratio. Emulsion protein load values were highest at low oil/protein ratios. ME of the dried emulsions was not affected by homogenization pressure but decreased from 89.2 to 18.8% when the oil/protein ratio was increased from 0.25 to 3.0, respectively. Mean particle sizes of reconstituted dried emulsions were greater than those of the original emulsions, particularly at high oil/protein ratios (>1.0), suggesting destabilization of high-oil emulsions during the spray-drying process.

Emulsions of gum arabic solutions (10% w/w) and soya oil at oil/gum ratios of 0.25−5.0 were prepared by homogenization at 20 MPa. The resulting emulsions were subsequently spray-dried to produce powders with oil contents ranging from 20 to 82% (w/w). Lipid globule size distributions and viscosities of the emulsions were determined, and particle size and percentage of extractable oil were determined for the spray-dried powders. The ability of the powders to redisperse in water was also examined. The average lipid globule size (D 4,3) (0.57 μm) did not vary significantly (P > 0.05) as the oil/gum ratio was increased from 0.25 and 1.0, but it did increase at higher ratios to a maximum of 2.02 μm. The average particle size of the spray-dried emulsions was within the range 9−17 μm, and the microencapsulation efficiency decreased from 100 to 48% when the oil/gum ratio was increased from 0.25 to 5.0, respectively. Powders with an oil content <50% dispersed readily in water. Keywords: Gum arabic; emulsions; microencapsulation; lipid globule size distribution

Emulsions containing various levels of soya oil dispersed in solutions of whey protein concentrate (WPC) 75 (5% w/v) were spray-dried to yield powders with oil contents ranging from 20% to 75% (w/w). The effect of homogenizing pressure and oil/protein ratio on oil globule size distributions and protein load of the emulsions and the microencapsulation efficiency (ME) and redispersion behavior of the powders were examined. Emulsion oil droplet size decreased with increasing homogenization pressure but was not affected by oil/protein ratio. Emulsion protein load and ME of the powders were negatively correlated with increasing oil/protein ratio. Powders with an oil/protein ratio Ͻ Ͻ Ͻ Ͻ Ͻ 0.75 were least susceptible to destabilization during spray-drying.

Gum arabic solutions (10% w/v) were emulsified with soy oil at oil/gum ratios of 0.25-5.0. At oil/gum ratios <1.0, it was established that gum arabic could be partially replaced with a nonsurfactant carbohydrate. To assess different carbohydrates as replacers for gum arabic, emulsions and spray-dried emulsions of soy oil and mixed solutions (10% w/v) of gum arabic and a range of carbohydrate wall materials (oil/gum = 0.5) were prepared and analyzed. Maize starch and glucose were ineffective as partial replacers of gum arabic, but maltodextrins of various dextrose equivalence values (5.5-38) successfully replaced 50% of the gum arabic. The microencapsulation efficiency of the gum arabic/maltodextrin stabilized powders was further increased by increasing total solids of the feed to the dryer and by increasing the atomizer nozzle diameter.