The study, published in LWT - Food Science and Technology, compared the emulsifying properties of major canola protein fractions - including albumin and globulin fractions - to previously studied canola protein isolates and to commercially available soy protein isolate.
Led by Siong Tan from Charles Sturt University, Australia, the research team revealed that the emulsion forming properties of canola globulin fractions were better than both canola albumin and canola protein isolate (CPI) in all cases - and had better emulsion forming properties than SPI, though only at acidic pH ranges.
"This study demonstrates the comparable emulsifying properties (forming or stabilizing) of some canola proteins to commercially available SPI, suggesting the potential use of canola proteins in food applications," wrote Tan and his colleagues.
"The globulin fraction had higher emulsifying capacity (EC), higher emulsifying activity index (EAI), and the droplet size of emulsions it stabilized was consistently smaller irrespective of pH compared to albumin fraction or CPI," they revealed. "In comparison to SPI, globulin fractions also had higher EC at all pH values tested, higher EAI at acidic pH, and smaller or comparable average emulsion droplet size at both pH 4 and 7."
Tan and colleagues compared the emulsifying properties of canola protein albumin fraction, globulin fraction, canola protein isolate (CPI), and commercial soy protein isolate (SPI) various pH values. The emulsifying properties were studied by analysing emulsifying capacity (EC), emulsifying activity index (EAI), and average droplet size at a range of pH 4 to 9.
The stability of emulsions formed was also studied, in terms of changes in particle size and changes in physical attributes of the emulsions during storage.
Globulin fractions were found to have better emulsion forming ability (higher EAI and EC), and the average droplet size of emulsions it stabilized was consistently smaller irrespective of pH compared to albumin fraction or canola protein isolate (CPI), said the team.
"In comparison to SPI, globulin fractions also had higher EC at all pH tested, higher EAI at acidic pH, and smaller or comparable average emulsion droplet size at both pH 4 and 7."
Indeed, stability of canola protein based emulsions were found to be comparable to those of SPI based emulsions at most pH values - except the emulsion stabilized by the CPI at pH 4- with no significant changes in droplet size during storage for up to 7 days at room temperature.
"These emulsions, however, experienced separation into the emulsion and serum phases after 24 h storage at room temperature with the exception of CPI- and SPI-stabilized emulsions at pH 9," the researchers wrote.
Source: LWT - Food Science and Technology
Published online ahead of print, doi: 10.1016/j.lwt.2013.12.040
"Emulsifying properties of proteins extracted from Australian canola meal"
Authors: Siong H. Tan, Rodney J. Mailer, et al