Writing in the journal Food Chemistry, researchers from China report that peanut protein formed a chemical complex with dextran that “remarkably improved” thermal stability and functional properties of the peanut protein isolates (PPI).
They explained mixing the protein isolates with the polysaccharide dextran, and heating them to cause a Maillard reaction, led to the protein and dextran forming chemical bonds (conjugates).
“The functional properties of PPI were remarkably improved by conjugation with dextran by dry-heating for up to 7 days,” said the researchers, led by Mouming Zhao from the South China University of Technology, China.
“In comparison with PPI, mixture and conjugates had more compacted tertiary conformation but exhibited better thermal stability, protein solubility, emulsifying and foam properties,” they added.
Zhao and his colleagues explained that the mixture of dextran with peanut protein could mean that peanut protein isolates can compete with other protein isolates such as soy and whey in terms of food applications.
Peanut potential
The authors noted that the peanut is the one of the most important oilseeds globally, adding that peanut proteins “have good nutritional quality with high essential amino acid content, which can easily be extracted to produce peanut protein isolate.”
They said that whilst peanut protein isolates have a higher purity of proteins and better functional properties than other peanut protein products – such as flour or concentrate – compared with other plant proteins – such as commercial soy protein isolate – its functional properties are much lower, “which might greatly limit the application of peanut proteins in many food formulations.”
As a result, much research has been dedicated to improving the functional properties of peanut proteins. Zhao noted that recently, the possibility of using the Maillard reaction between proteins and polysaccharides has been investigated as a possible method to improve the functional properties of protein isolates.
“Several proteins, such as whey proteins, beta-lactoglobulin, ovalbumin, lysozyme, rice proteins and soy proteins, have been conjugated with various sugars, in order to improve their functionality and heat stability properties,” said the researchers.
“However, little information is available about the Maillard reaction with polysaccharides to modify functional properties of PPI,” they noted.
The new study investigated the effects of a dry-heated Maillard reaction between PPI and dextran.
Zhao and his colleagues mixed the peanut protein with dextran (1:1 weight ratio), before they were dry heated at 60 °C and 79% relative humidity for 7 days.
They reported that analysis of the products revealed that the PPI had become complexed with dextran to form conjugates of high molecular weight, whilst the emulsifying and foaming properties of the conjugated samples were also improved.
Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodchem.2011.09.074
“Improvement of functional properties of peanut protein isolate by conjugation with dextran through Maillard reaction”
Authors: Y. Liu, G. Zhao, M. Zhao, J. Ren, B. Yang