Composition and stability of anthocyanins in blue-grained wheat

Wheat grain is recognized as a good source of potentially health-enhancing components such as dietary fiber, phenolics, tocopherols, and carotenoids. Anthocyanins, another group of bioactive compounds, are found in blue and purple wheat grains. In the present study, a blue aleurone spring wheat line "Purendo 38" with relatively high content of total anthocyanins was used to investigate the composition and stability of anthocyanins over three crop years. Commercial cultivars of purple (Konini) and red (Katepwa) wheats were included in the study. Separation of anthocyanins by high-performance liquid chromatography (HPLC) showed that each wheat had a distinct anthocyanin profile. Four major anthocyanins were separated from blue wheat extracts as compared to five anthocyanins in purple wheat. Cyanidin 3-glucoside was the predominant anthocyanin in purple wheat, whereas it was the second major anthocyanin in blue wheat. The predominant anthocyanin in blue wheat, making up approximately 41% of the total anthocyanin content, remains to be structurally unidentified. Blue wheat anthocyanins were thermally most stable at pH 1. Their degradation was slightly lower at pH 3 as compared to pH 5. Increasing the temperature from 65 to 95 degrees C increased degradation of blue wheat anthocyanins. Addition of SO(2) during heating of blue wheat had a stabilizing effect on anthocyanin pigments. The optimal SO(2) concentrations were 500-1000 ppm for whole meals and 1000-3000 ppm for isolated anthocyanins. Further studies are underway to identify and verify individual anthocyanins in blue wheat and their potential end uses.