Cysteine residues are responsible for the sulfurous off-flavor formed in heated whey protein solutions

Chengkang Li; Peter A Paulsen; Halise Gül Akıllıoğlu; Søren B Nielsen; Kasper Engholm-Keller; Marianne N Lund

doi:10.1016/j.fochms.2022.100120

Cysteine residues are responsible for the sulfurous off-flavor formed in heated whey protein solutions

Food Chem (Oxf). 2022 Jul 12:5:100120. doi: 10.1016/j.fochms.2022.100120. eCollection 2022 Dec 30.

Authors

Chengkang Li¹, Peter A Paulsen², Halise Gül Akıllıoğlu¹, Søren B Nielsen², Kasper Engholm-Keller¹, Marianne N Lund^{1

3}

Affiliations

¹ Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 26, 1958 Frederiksberg, Denmark.
² Arla Foods Ingredients, Sønderupvej 26, 6920 Videbæk, Denmark.
³ Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.

Abstract

Odor-active volatile sulfur compounds are formed in heated food protein systems. In the present study, hydrogen sulfide (H₂S) was found to be the most abundant sulfur volatile in whey protein solutions (whey protein isolate [WPI], a whey model system and single whey proteins) by gas chromatography-flame photometric detector (GC-FPD) analysis after heat treatments (60-90 °C for 10 min, 90 °C for 120 min and UHT-like treatment). H₂S was detected in WPI after heating at 90 °C for 10 min, and was significantly increased at higher heat load (90 °C for 120 min and the UHT-like treatment). Site-specific LC-MS/MS-based proteomic analysis was conducted, monitoring desulfurization reactions in these protein systems to investigate the mechanism of H₂S formation in heated WPI. Cysteine residues from beta-lactoglobulin were found to be responsible for the formation of H₂S in heated WPI, presumably via beta-elimination.

Keywords: Beta-elimination; GC-FPD and LC-MS/MS; Hydrogen sulfide; Volatile sulfur compound; β-lactoglobulin.