Antioxidative activity of barley hordein and its loss by deamidation.

Barley hordein was comparable to maize zein in antioxidation under a powder model system. Various deamidated "hordein" preparations were obtained and examined for their molecular-size distribution (by Sephacryl S-100 gel filtration), hydrophobicity (by fluorescence measurement using fluorescent probes) and antioxidative activity (by the ferric thiocyanate method). Deamidation caused fragmentation of the hordein molecule and simultaneously lowered its fatty acid-binding capacity rather than its surface hydrophobicity. Then, the antioxidative activity diminished with increasing deamidation. When the fatty acid-binding capacity was plotted against the antioxidative activity, a high correlation (r2 = 0.92) was observed between these two events.