Amaranth Protein Isolates at the Air-Water Interface.

BOLONTRADE, AGUSTÍN J.; ROPERS, MARIE-HÉLÈNE; SCHWIEGER, CHRISTIAN; SCILINGO, ADRIANA A.; AÑÓN, M. CRISTINA; ANTON, MARC

Quebec, Canadá

Congreso; 13th International Conference on Organized Molecular Films.; 2010

Faculté de médecine, Université Laval

Amaranth is a grain mostly harvested in subtropical and some tropical regions of AsiaAfrica and America where it constituted traditional meals. The renewal of interest for its crop liesin its nutritional value: the seed contains a higher protein value than other cereals and its essentialamino acid composition is close to the optimum required in the human diet. Its high nutritionalvalue, coupled with interesting functional properties, led us to ask whether these proteins couldbe used as dispersing agents in food products to get a better balance in essential amino acid.Amaranthus hypochondriacus isolate proteins were extracted from defatted seed flours.The surface activity of their soluble extracts was studied at pH 2 and 8 at the air-water interface.The soluble extract at pH 2 exhibits a better surface activity and a significantly higher viscousmodulus than the soluble extract at pH 8. The spectra obtained by Infrared Reflection AbsorptionSpectroscopy (IRRAS) revealed that the film thickness increases more weakly at pH 2 than at pH8 during the compression of the film. The simulation of spectra obtained by angular variationindicates that the proteins re-organise more significantly at the interface at pH 2 than at pH 8. AtpH 2, amaranth proteins suffer a significant denaturation and dissociation, whereas at pH 8 thenative structure is preserved. This structural difference explains the different behaviors at theinterface.These results orient the single use of amaranth protein isolates to acidic pH while mixedfilms with other proteins must be considered at higher pH.