Grants and Contracts Details
Description
Soybeans are the second largest food crop in the U.S. with about 3 billion bushels
produced in 2001. In 2000, only about 1.5 percent of the available protein from soybeans was
used in human foods largely because of their characteristic flavor. The removal of
methanethiol and dimethyl trisulfide from aqueous slurries of isolated soy protein and soymilk
has been shown to significantly improve the odor of these products. A basic understanding of
the mechanism, and reactants, involved in the formation of these odorants is necessary for the
development of commercially practical solutions to the longstanding flavor problem associated
with soy protein products.
Our preliminary results strongly suggest that the formation of methanethiol in aqueous
slurries of isolated soy proteins is an ongoing process involving all, or part, of a sulfur
metabolism responsible for the conversion of sulfate-to-cysteine. Similar mechanisms have
been reported in soybean leafs and seeds (developing and mature), as well as in other plants.
This is a mechanism unlike any other previously reported in foods. We propose to monitor the
levels of the most likely metabolites (reactants) including free amino acids (particularly
cysteine), sulfates and sulfides (e.g., adensosine-5'phosphosulfate and hydrogen sulfide), and
methyl donors (e.g., S-adenosylmethionine, methyl-tetrahydrofolate, choline/betaine and
methylcobalamin). This will be done under a variety of conditions to determine the effect that
treatments have on the pool of each reactant and determine how they relate to the formation of
methanethiol. We will also track isotopic-labeled sulfur from L-cysteine with an emphasis on
hydrogen sulfide and methanethiol. After the primary reactants have been identified and
plausible mechanisms proposed, we will attempt to isolate the most likely enzymes (catalysts)
affecting the formation of methanethiol.
Status | Finished |
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Effective start/end date | 11/1/03 → 10/31/06 |
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