The study claims acylation of soy proteins with saturated fatty acids (SFA) resulted in improved physico-chemical functionalities, which have potential in functional food formulation and processing.
“It was demonstrated that saturated fatty acids with adequate chain length are suitable candidates for the preparation of functional lipoproteins from soy proteins,” wrote the researchers, led by Dr. Soichiro Nakamura at Shinshu University, Japan.
Poor Functionality
Soybean proteins are a well established source of nutrients, and a potential source of bioactive peptides. But soy globulin proteins have poor functionality, making them difficult to be used directly in emulsions for functional foods.
Demand for multi-functional foods and ingredients is creating pressure on food industries and researchers to develop modification techniques “to enhance and diversify … protein functionalities”, stated the researchers.
Various modification techniques – including acylation – have been used in attempts to change soy proteins structural, physical and chemical properties
Acylation is a chemical reaction where an acyl group is joined to part of a molecule. The acylation of free amino groups on emulsion proteins affects the molecule’s charge balance and functional characteristics.
In the new study, the effects of acylation on emulsifying properties of soy globulins were investigated using a variety of saturated fatty acids.
Enhanced Emulsifiers
The soy globulins, beta conglycinin (7S), glycinin (11S), and acid-precipitated protein (APP) were acylated with activated fatty acid esters (6C–18C) forming linkages between the fatty acid and free amino groups of soy protein.
The research reports activity and emulsion stability of 7S and 11S to be significantly improved upon acylation with all saturated fatty acids - whereas no changes in activity or stability were found for APP from acylation with short or long chain fatty acids.
Medium chain saturated fatty acids were found to be suitable in enhancing the emulsifying properties of all soy globulins (7S, 11S, APP).
Fluorescence intensity was also notably affected by acylation, suggesting the reaction caused significant changes in protein structure.
Successful improvement
“The functional properties of soy proteins were successfully improved following acylation with a variety of naturally occurring fatty acids,” wrote the researchers.
The authors highlighted the significantly improved surface functionalities displayed by acylated beta-conglycinin (7S).
“The enhanced surface functionalities could be useful in functional food formulation and processing,” concluded the authors.
Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodchem.2010.06.081
“Improved emulsifying properties of soy proteins by acylation with saturated fatty acids”
Authors: A.O. Matemu, H. Kayahara, H. Murasawa, S. Katayama, S. Nakamura