The project was supported by the Natl. Research Initiative of the USDA Cooperative State Research, Education and Extension Service, grant nr 2004-35503-14113. It is published with the approval of the Director of the Kentucky Agricultural Experiment Station as Journal Article nr 05-07-112.
A ≥ 100000-MW Soybean Protein Fraction that Inhibits the Formation of Methanethiol and Hydrogen Sulfide in Aqueous Slurries of Isolated Soy Proteins with Added L-Cysteine
Article first published online: 30 JUN 2006
Journal of Food Science
Volume 71, Issue 3, pages C185–C189, April 2006
How to Cite
Boatright, W. L. and Lu, G. (2006), A ≥ 100000-MW Soybean Protein Fraction that Inhibits the Formation of Methanethiol and Hydrogen Sulfide in Aqueous Slurries of Isolated Soy Proteins with Added L-Cysteine. Journal of Food Science, 71: C185–C189. doi: 10.1111/j.1365-2621.2006.tb15615.x
- Issue published online: 30 JUN 2006
- Article first published online: 30 JUN 2006
- MS 20050636 Submitted 10/21/05, Revised 11/28/05, Accepted 1/6/06.
- soy protein;
- hydrogen sulfide;
ABSTRACT: The addition of L-cysteine to aqueous slurries of commercial isolated soy proteins (ISP) increased methanethiol headspace levels by 17- to 36-fold over the control. Corresponding levels of hydrogen sulfide were about 10 to 19 times greater than methanethiol. Neither methanethiol nor hydrogen sulfide were detected when L-cysteine was added to aqueous slurries of hexane-defatted soy flour. The production of hydrogen sulfide and methanethiol in aqueous slurries of commercial ISP was inhibited by the addition of a component(s) recovered from the pH 4.6 supernatant obtained during laboratory preparation of ISP by isoelectric precipitation. The inhibitory component had a molecular weight (MW) of ≥ 100000 and an isoelectric point of about 5.9. This component was not serine acetyl transferase. Its inhibitory properties were inactivated at 70°C and diminished with elevated levels of methionine. Adding the ≥ 100000-MW soluble-proteins (from the isoelectric precipitation step) back to a nonheat-treated laboratory ISP during processing reduced the methanethiol level by 88%.