Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2006
Publication Date: 1/1/2007
Citation: Downing, J.M., Chung, O.K., Seib, P.A., Hubbard, J. 2007. Pressurized solvent extraction of genistein and its beta-glucoside conjugates from soybean flours and soy-based foods. Cereal Chem. 84(1):44-47.
Interpretive Summary: Soy protein isolates, soy flour and other soy preparations can be found in many food products, including baked goods and meat substitutes. The soy isoflavone genistein can be found in almost all of these foods. Genistein has been shown to be bioactive, mimicking the effects of estrogen and earning genistein the classification of a phytoestrogen. Genistein could have pharmaceutical uses in the treatment of heart disease and cancer. The amount of genistein found in different foods varies widely, requiring chemical analysis to determine the amount or dose of genistein found in each soy preparation. Pressurized solvent extraction (PSE) analysis utilizes high pressure and heat to rapidly extract analytes from complex matrices. The work presented here utilizes PSE to quantify the amount of genistein found in soy flours and several common soy based foods. Amounts of genistein in the foods were determined by PSE and a common stirring method. The results of this study showed that the amount of genistein extracted by PSE was comparable to the stirring method. The PSE method is automated and requires less time than some common methods. The method could be utilized research settings or in industrial quality control and could be scaled up for processing of soy foods.
Technical Abstract: Genistein, the prominent isoflavone found in soybeans may have several health benefits, including the lowering of the risk of heart disease and cancer. In this investigation, genistein and its glucoside conjugates were extracted from samples of five ground soybeans (flours) and three soy food products in a total of 20 min by a pressurized solvent extraction (PSE) system using 80% (v/v) aqueous (aq) methanol. The PSE method involved pressuring 80% (v/v) aq methanol to 138 bar (2000 psi) for a 1-min static extraction at 80' C followed by a 10-mL dynamic extraction. The PSE method was compared to a atmospheric extraction method that utilized stirring a ground sample in 80% aq methanol for 1 hr. Genistein and its glucoside moieties in extracts were quantified by HPLC using a 4.6x150 mm reverse-phase (C8) column with a 0.1% triflouroacetic acid / acetonitrile linear gradient. The PSE and stirring methods gave comparable levels of genistein equivalents in five soybean flours and three soy-based foods. Applications of this methodology would be the routine analysis of genistein in research and development and quality control. Advantages of this method are 1/3 less time for rapid extraction (2/3 less time than stirring) and automatic sample handling.