Changes in Protein Quality and Antioxidant Properties of Buckwheat Seeds and Groats Induced by Roasting

Abstract

This study focused on the evaluation of changes in protein quality and antioxidant properties of buckwheat seeds and groats induced by roasting. Changes in protein quality were indirectly measured by Maillard reaction chemical indicators such as furosine, FAST index, and browning. Characterization of antioxidant profiles of raw whole seeds, roasted whole seeds, raw groats, and roasted groats was undertaken by determining the extractable total phenolic compounds (TPC), extractable total flavonoids (TF) and individual flavonoids, lipophilic and hydrophilic peroxyl radical scavengers by ORAC(FL) assay, and scavengers of ABTS radical cations by TEAC assay. Roasting significantly decreased the total protein content of groats, whereas this parameter was not affected by the thermal treatment of whole seeds. The formation of MRPs was induced by the thermal treatment of both whole seeds and groats, thus suggesting deterioration of protein quality due to this chemical event. A significant degradation in natural antioxidants due to thermal processing was observed. Most of the peroxyl radical scavenging activity of samples was associated with hydrophilic compounds because L-ORAC(FL) values were on average 9% of the H-ORAC(FL) values. The H-ORAC(FL) values were positively correlated with extractable TPC contents (r = 0.51) and extractable TF contents (r = 0.93), whereas they showed a negative correlation with furosine (r = -0.87), FAST index (r = -0.85), and browning (r = -0.98) results.