Stability of Sorgum Bicolor Alcoholic Extract as affected by pH and Temperature

Storage stability of Sorghum bicolor alcoholic extract as affected by pH and temperature

Jordan Bradwell, Philipus Pangloli, Vermont P Dia

Department of Food Science and Technology, University of Tennessee Institute of Agriculture, Knoxville TN

Red sorghum contains phytochemicals such as 3-deoxyanthocyanidins and flavonoids with potential application in food as coloring and health promoting agents. The objective was to determine the stability of methanolic and ethanolic extracts of sorghum as affected by pH (2, 4 and 6) and temperature of storage (4 and 22 °C). The following parameters were measured: polyphenol concentration, absorbance at 490 nm and L*, a* and b*-values to monitor changes in color, and concentrations of luteolin, apigenin and naringenin by high performance liquid chromatography. After 10 weeks, polyphenols did not change significantly at pH 2 and 4 samples stored at 4 and 22 °C, but reduced by 58.4% in pH 6 sample for ethanolic extract and by 42.5% for methanolic extract at 22 °C. Extracts with pH 2 and 6 stored at 22 °C led to increase in absorbance at 490 nm and reduction in L-values indicating darkening of the extracts which may be associated with browning reaction. Luteolin, apigenin and naringenin were reduced after 10 weeks of storage indicating degradation of these flavonoids. Our preliminary results are important in determining proper storage conditions in order to protect phytochemicals in red sorghum for potential use in food products.