Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2010
Publication Date: 6/18/2010
Citation: Correa, C.R., Li, L., Aldini, G., Carini, M., Chen, O., Chun, H., Cho, S., Park, K., Russell, R.M., Blumberg, J.B., Yeum, K. 2010. Composition and stability of phytochemicals in five varieties of black soybeans (glycine max). Food Chemistry. 123:1176-1184. Interpretive Summary: The nutrient components of five different types of black soybeans were determined, as well as how long these components were stable at room temperature, 4 degrees celsius and -80 degrees celsius over 14 months. Furthermore, various sophisticated instruments were utilized to analyze chemical components in these black soybeans. The amount of a specific form of vitamin E (y-tocopherol), fat-soluble pigment (lutein) contained in five different types of black soybeans are varied. Organic compounds, total phenols, in black soybeans stored at room temperature, 4 degrees celsius or -80 degrees celsius were stable for 14 months. On the other hand, vitamin E (y-tocopherol) and fat-soluble pigment (lutein) contained in black soybeans rapidly degraded within a month at room temperature. The current study indicates that black soybeans are a rich source of vitamin E and phenols, and that levels vary depending upon types. In addition, storage at low temperatures is recommended to reduce the loss of fat-soluble nutrient components in black soybeans over an extended period of time. This study provides essential information for the development of dietary supplement using this plant food.
Technical Abstract: Phytochemical compositions of five varieties of black soybeans (Glycine max) and their stabilities at room temperature, 4 deg.C and -80 deg.C over 14 months were determined by HPLC systems with electrochemical (HPLC-ECD) and UV detectors. Polyphenol profiling was carried out by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) with an orbitrap as a mass analyzer in both positive and negative ion modes, and polyphenols in aglycone forms were quantified by HPLC-ECD. Five different varieties of black soybeans (Glycine max) contained 249-405 g dry weight of y-tocopherol and 6.76-14.98 g dry weight of lutein. Major polyphenols in black soybeans (Glycine max) were daidzein (193-288 g dry weight) and genistein 145-223 g dry weight), mainly presents as glucosides and acetyl glucosides. No significant decrease was found in total phenols of stored black soybeans (Glycine max) stored at room temperature, 4 deg.C or -80 deg.C for 14 months. On the other hand, lutein and y-tocopherol degraded significantly within a month of storage at room temperature (p<0.01), whereas they remained stable up to 6 months at 4 deg.C and up to 14 months at -80 deg.C. The current study indicates that black soybeans (Glycine max) are a rich source of y-tocopherol and phenols (isoflavones, flavonols, flavan-3-ols, proanthocyanidins and anthocyanin) and that the levels vary depending upon varieties. In addition, storage at low temperature is recommended to reduce the loss of fat- soluble phytochemicals in black soybeans (Glycine max) over an extended period of time.