A ≥ 100000-MW soybean protein fraction that inhibits the formation of methanethiol and hydrogen sulfide in aqueous slurries of isolated soy protiens with added L-cysteine

William L. Boatright, Guiping Lu

Research output: Contribution to journalArticlepeer-review

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 suffide 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 transfe̊rase. 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%.

Original languageEnglish
Pages (from-to)C185-C189
JournalJournal of Food Science
Volume71
Issue number3
DOIs
StatePublished - Apr 2006

Keywords

  • Hydrogen sulfide
  • L-cysteine
  • Methanethiol
  • Soy protein

ASJC Scopus subject areas

  • Food Science

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