VARIABILITY OF PROTEINS, FLAVOR CONTRIBUTORS, AND FOOD PRODUCTS AMONG FOUR WINGED BEAN SELECTIONS

MARK WINN JENSEN, Purdue University

Abstract

Winged bean, Psophocarpus tetragonolobus (L.) DC., is a tropical legume with tremendous potential for meeting dietary protein needs. It can be developed as a suitable crop for the peoples of Southeast Asia, Africa, Central and South America, and the Pacific. In order to facilitate improvement in winged bean for its use as human food, extensive background research is necessary for breeding programs. Such programs should consider factors relating to protein content, flavor contributors, and properties of winged bean food products (such as tofu and tempeh, traditional East Asian foods). This research was designed to examine the variability of the factors mentioned above among four winged bean selections (TPT-1, TPT-2, TPT-6, and Chimbu). Whole seeds, tofu, and tempeh were evaluated. Specifically, protein and amino acid (especially methionine and tryptophan) content, lipid and fatty acid content, lipoxygenase activity, Tetrahymena Protein Efficiency Ratio values, and tocopherol content were determined. Protein contents, as determined from Kjeldahl nitrogen, indicated that the selection TPT-1 was significantly higher in protein than the other three selections for the whole seeds, cotyledons, hulls, tofu, and tempeh analyzed. Amino Acid analyses showed that Chimbu was higher in leucine for whole seeds, tofu, and tempeh than the other selections. Chimbu was lower than the other three selections in threonine in whole seeds and tempeh. Other significant differences in amino acid contents were: lower phenylalanine in Chimbu tofu, lower valine in TPT-2 tofu, lower leucine in TPT-1 tempeh, and higher leucine in TPT-2 seeds. Methionine was determined by a gas chromatographic method based on the ability of cyanogen bromide to cleave methionine to yield methylthiocyanate which was quantitated. There was no significant differences among the seeds, tofu, or tempeh from the four winged bean selections analyzed. Tryptophan was determined separately on whole seed samples which were enzymatically digested by Pronase. The amino acids in the digests were separated using a column of Amberlite (IR-120H) cation exchange resin and then analyzed on an automated system. There were no significant differences in tryptophan concentrations among the winged bean selections. Lipid content of whole seeds, tofu, and tempeh was highest in the selection Chimbu and lowest in TPT-1. Methyl esters of the fatty acids (analyzed by gas chromatography) showed variation for each fatty acid among the four selections. However, the total content of unsaturated or saturated fatty acids were not significantly different among the winged bean selections. Lipoxygenase activity (a factor in off-flavor production) was determined in seeds spectrophotometrically. The specific activity of this enzyme was not significantly different among the four winged bean selections tested. A rapid protein quality assay was performed with the protozoan Tetrahymena pyriformis WH(,14). The Tetrahymena Protein Efficiency Ratio (T-PER) values for whole seeds showed that Chimbu was higher than the other three selections. There were no differences in T-PER values for tofu made from the four selections. T-PER values for tempeh indicated that tempeh made from Chimbu was lower than the other three winged bean selections. Total seed tocopherols were analyzed by thin-layer chromatography. There were no observed differences in tocopherol content among the four winged bean selections.

Degree

Ph.D.

Subject Area

Food science

COinS