ARS | Publication request: Variance in the chemical composition of dry beans determined from UV spectral fingerprints

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2008
Publication Date: September 4, 2009
Citation: Harnly, J.M., Pastor Corrales, M.A., Luthria, D.L. 2009. Variance in the chemical composition of dry beans determined from UV spectral fingerprints. Journal of Agricultural and Food Chemistry. 57(19):8705-8710.

Interpretive Summary: In this study, 9 varieties of dry beans were grown in 3 states. The plot for each variety in each state consisted of 8 rows. All the beans for each row were composited and a representative sample was extracted using a water-methanol solution and analyzed 3 times by UV molecular absorbance, an inexpensive analytical method. The experimental design allowed us to identify the chemical difference (the variance) associated with each of the variables (state where grown, variety, and row). In addition, since we knew the number of plants in each row, we could calculate the variance arising from chemical differences between each plant. This unique data set shows that 70% to 80% of the total variance arises from plant-to-plant differences, followed by variety differences (7% to 10% of the total variance) and differences due to the growing location (less than 1% of the total variance).

Technical Abstract: Nine varieties of dry beans representing 5 market classes were grown in 3 states (Maryland, Michigan, and Nebraska) and sub-samples were collected for each variety (row composites from each plot). Aqueous methanol extracts were analyzed in triplicate by UV spectrophotometry. Analysis of variance-principal component analysis (ANOVA-PCA) was used to quantify the relative variance arising from location, variety, between row, and analytical uncertainty and to test the significance of differences in the chemical composition. Statistically significant differences were observed between all 3 locations, all 9 varieties, and most rows. PCA score plots showed that the 9 varieties could be placed in four categories: 1) black beans (cv jaguar and cv T-39), 2) pinto beans (cv Buster and cv Othello), 3) small red beans (cv Red Merlot), and 4) Great Northern (cv Matterhorn and cv Weihing) and Navy (cv Seahawk and cv Vista) beans. After conversion of between row variance to between plant variance the final relative variance contributions for location (0.7%), variety (21.6%), plant (38.0%), and analytical uncertainty (2.0%) were determined.