Substantial progress has been made in understanding the basic chemical and structural properties of the principal whey proteins, that is, beta-lactoglobulin (beta-Lg), alpha-lactalbumin (alpha-La), bovine serum albumin (BSA), and immunoglobulin (Ig). This knowledge has been acquired in terms of: (1) procedures for isolation, purification, and characterization of the individual whey proteins in buffer solutions; and (2) whey fractionation technologies for manufacturing whey protein concentrates (WPC) with improved chemical and functional properties in food systems. This article is a critical review of selected publications related to (1) whey fractionation technology for manufacturing WPC and WPI; (2) fundamental properties of whey proteins; and (3) factors that affect protein functionality, that is, composition, protein structure, and processing.

A colaborative study was conducted to develop a rapid, simple and reliable procedure for determining the solubility of food protein products, e.g., spray-dried whey protein concentrate, sodium caseinate, egg white protein and soy protein isolate. The procedure was developed by modifying the nitrogen solubility index (NSI) procedure. Protein content and soluble protein were determined by micro-Kjeldahl or biuret procedures with standard deviations of ? 0.83-4.12 for all proteins except caseinate which had a value of Y? 13.95. Although the biuret and micro-Kjeldahl procedures generally provided comparable accuracy and precision for protein content and solubility of certain proteins, the biuret procedure exhibited considerable error and variability for other proteins.

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