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
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