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
Effects of glycerol, xylitol, and sorbitol on selected physical properties of whey protein isolate (WPI) films were examined. Increasing glycerol or sorbitol content led to increases in moisture content, water vapor permeability, and % elongation; and decreases in tensile strength, elastic modulus, and glass transition temperatures of the films. Increasing levels of xylitol had no effect on permeability, moisture content, or glass transition temperature of the films, but decreased % elongation, tensile strength, and elastic modulus. Moisture content of the films correlated well with glass transition temperatures. Differences in measured physical properties of films with plasticizer type and concentration may be attributed to differences in the hygroscopic and crystalline properties of the plasticizers.
Imitation cheeses containing 3% native maize, waxy-maize, wheat, potato or rice starch were manufactured and the microstructure, meltability, texture and dynamic rheology of these products were compared to a control (0% starch). Fat globules in starch-containing products (except potato) were smaller than in the control as evidenced by electron microscopy. All starches reduced meltability and cohesiveness of the imitation cheeses. Hardness was increased by wheat, potato or maize starch but reduced by waxy-maize or rice starch. Starches significantly reduced tan ␦ peaks compared to the control with potato starch having the greatest effect. Rice starch appears to have the most potential as a partial casein substitute in imitation cheese.
Imitation cheese was manufactured with various levels of pre-gelatinized maize starch. Melt characteristics were assessed by an empirical melt test, based on the Olson and Price method. Using dynamic rheology, the storage modulus (G9), the loss modulus (G0) and the loss angle (tan d) were measured as a function of temperature (22-100°C). Meltability decreased with increasing levels of starch. Maximum tan d values and the temperature at which they occurred decreased with increasing starch levels. A high correlation (r 2 = +0.96) was found between the maximum tan d values and meltability as assessed by the empirical method. Tan d may be a useful indicator of imitation cheese meltability.
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