The encapsulation properties of several commercial food proteins and gum arabic (GA) were evaluated by conventional analytical procedures and dynamic headspace analysis (DHA). The microstructural properties of spray-dried microencapsulated orange oil emulsion particles were investigated by scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM). Soy protein isolate (SPI) was most effective and whey protein isolate (WPI) least effective for retaining orange oil during spray-drying of the liquid orange oil emulsions. Spray-dried SC-microencapsulated particles exhibited the largest sizes, and the sizes of the other microencapsulated orange oil particles were in decreasing order of WPI > SPI > GA. SEM and CSLM results revealed that spray-dried GA-microencapsulated orange oil particles had undergone more shrinkage during drying than the protein-microencapsulated products. A modified DHA technique was developed to determine the rate of release of volatiles from the spray-dried, microencapsulated orange oil emulsion particles. DHA results revealed that GA-microencapsulated particles had the highest volatile release rate and SPI-microencapsulated particles the lowest release rate as determined by DHA. WPI- and SPI-microencapsulated orange oil products were more stable against oxidation than SC- and GA-microencapsulated orange oil products. It was concluded that GA and SC were least effective as orange oil microencapsulants on the basis of DHA results and WPI and GA were least effective as orange oil microencapsulants on the basis of total oil retention and surface oil results. Keywords: Encapsulation; flavor release; protein; microstructure; dynamic headspace analysis

The comparative suitability of gum arabic (GA), soy protein isolate (SPI), whey protein isolate (WPI), and sodium caseinate (SC) for use as food flavorant encapsulants was investigated in this study by determining their ability to form small-sized, physically stable orange oil emulsion particles by high-pressure homogenization. The resulting emulsion particles were evaluated for their microstructural properties, physical stability, and droplet size distribution as a function of oil content and homogenization pressure. SPI-emulsified orange oil droplets were most stable and GA-emulsified orange oil droplets were least stable against creaming during 10 days of storage at room temperature. Light scattering results revealed that SC was most effective and SPI was least effective for producing orange oil emulsion droplets of ≤4 μm diameter by high-pressure homogenization. Transmission electron microscopy images revealed that SPI-emulsified orange oil droplets were surrounded by the thickest membrane structures but that GA-stabilized emulsion particle membranes did not fully surround the orange oil droplets. Statistical analysis revealed a significant interaction between several independent variables, i.e., encapsulant type and percent oil load, and two of the dependent variables, i.e., droplet size and depth of cream layer. No interaction was observed between emulsifier/encapsulant type and homogenization pressure at α = 0.05. Keywords: Emulsification; encapsulation; proteins; gum arabic; microstructure

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Emulsifying properties of six experimental and three commercial control, lipid-reduced, and calcium-reduced whey protein concentrates (WPC) were evaluated on the basis of mean droplet size and creaming intensity in model emulsions. Mean droplet sizes ranged from 225 to 395 nm. Model emulsions made with a commercial control (WPC F), experimental lipid-reduced (WPC MF.1, MF.45), commercial lipid-reduced (WPC E), and experimental calcium and lipid-reduced (WPC B) samples had low stabilities. Emulsion stabilities of the WPC most strongly correlated with protein solubility and fatty acid compositions, but did not correlate with mean droplet size.