or= 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

• Published in: Journal of food science Vol. 71; no. 3; pp. C185 - C189
• Main Authors: Boatright, W.L, Lu, G
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.04.2006; Institute of Food Technologists; Wiley Subscription Services, Inc
• Subjects: Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts; Biological and medical sciences; chemical precipitation; cysteine; defatted foods; Enzymes; food contamination; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Hydrogen sulfide; inactivation temperature; inhibitors; isoelectric point; L-cysteine; methanethiol; methionine; molecular weight; odor compounds; protein isolates; Proteins; reaction inhibition; slurries; soy flour; soy protein; Soybeans; thiols; Cysteine; Hydrogen; Soybean; Glycine max; Soy protein; Grain legume; Sulfides; Leguminosae; hydrogen sulfide; Aminoacid; Dicotyledones; Angiospermae; methanethiol; L-cysteine; Spermatophyta
• ISSN: 0022-1147; 1750-3841
• DOI: 10.1111/j.1365-2621.2006.tb15615.x

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 greater than or equal to 100000 and an isoelectric point of about 5.9. This component was not serine acetyl transferase. Its inhibitory properties were inactivated at 70 degrees C and diminished with elevated levels of methionine. Adding the greater than or equal to 100000-MW soluble-proteins (from the isoelectric precipitation step) back to a nonheat-treated laboratory ISP during processing reduced the methanethiol level by 88%.