Physicochemical and structural characterisation of globulin and albumin from common buckwheat (Fagopyrum esculentum Moench) seeds

The physicochemical and conformational properties of globulin (BG) and albumin (BA) fractions from common buckwheat seeds were characterised, and compared with those of buckwheat protein isolate (BPI). The polyphenol contents were also evaluated. The polyphenol content in BA was much higher than that in BG, and most of the polyphenols in the BA was in the free form, whilst that in the BG and BPI was mainly in the protein-bound form. The BA had higher content of uncharged polar amino acids, but lower acidic amino acids than BG. The protein solubility-pH profile of the BG and BA were very different, especially at pH 4.0–6.0. Far-UV and near-UV CD and intrinsic fluorescence spectra indicated that the secondary and/or tertiary conformations of BA were much more flexible than those of BG, but also more easily affected by the polyphenols. The results indicated that the properties of BG and BA varied considerably, and were largely dependent upon their polyphenol levels and the interactions of the polyphenols and the proteins.