Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Foods and Nutrition

First Advisor

Chunyang Wang


Soy foods represent the only substantial dietary source of isoflavones, phytochemicals demonstrated to prevent a number of conditions associated with cancer and heart disease, both in vitro and in vivo. To date, twelve isoflavones have been identified in soybeans. The research objectives for this study were to measure isoflavone content in South Dakota soybean cultivars, to explore possible relationships between isoflavone contents and agronomic seed characteristics, and to develop an alternative analytical method for assaying isoflavone content in soy foods. The soybean sample set represented 210 varieties grown in Brookings, South Dakota. Their individual and total isoflavone contents were surveyed using high performance liquid chromatography. Total isoflavone content of the sample set ranged from 2041.2 µgig to 4803.7 µgig. A number of agronomic seed characteristics were documented for each variety. Isoflavone content was found to differ significantly based on soybean variety and maturity group. Hilum color was found to account for differences in genistin, daidzein, and genistein content. Linear relationships were established for genistein content and yield, maturity (in days), and plant height. No differences in isoflavone content were observed based on disease resistance profiles or seed weight of the samples. An alternative analytical method was developed using UV-Visible spectrophotometry. Thirty soy protein samples were scanned at 220 to 450 nm. Predictive equations for individual and total isoflavone content were derived from regression of HPLC-generated values on the absorbance values. The ability of the predictive equations to produce isoflavone content values approximating those obtained by high performance liquid chromatography was tested by linear regression analysis. Under these conditions this analytical method produced satisfactory predictions for all isoflavones in the sample, except acetyl genistin. UV-Visible spectrophotometry shows great potential as a quick and accurate screening tool.

Library of Congress Subject Headings

Soybean -- Varieties




South Dakota State University



Rights Statement

In Copyright