3-chlorotyrosine formation versus other molecular changes induced by hypochlorous acid in proteins: A study using dairy proteins as a model. (May 2016)

• Record Type: Journal Article
• Authors: Bao Loan, Huynh Nguyen; Kerkaert, Barbara; Cucu, Tatiana; Mestdagh, Frédéric; De Meulenaer, Bruno
• Is Part Of: Lebensmittel-Wissenschaft + Technologie =. Volume 68(2016)
• Page Start: 145
• Page End: 152
• Publication Date: 2016-05
• Subjects: 3-chlorotyrosine -- Whey proteins -- Caseins -- Hypochlorous acid -- pH; HOCl hypochlorous acid -- SDS-PAGE sodium dodecyl sulphate – polyacrylamide gel electrophoresis -- DNPH 2, 4-dinitrophenylhydrazine -- TCA trichloroacetic acid; 3-chlorotyrosine (PubChem CID: 110992) -- Sodium hypochlorite (PubChem CID: 23665760) -- Ethyl chloroformate (PubChem CID: 10928) -- Dichloromethane (PubChem CID: 6344) -- Pyridine (PubChem CID: 1049) -- Sodium sulphate (PubChem CID: 24436) -- Phenol (PubChem CID: 996) -- Ethanol (PubChem CID: 702) -- Trifluoroacetic acid (PubChem CID: 6422) -- Hydrochloric acid (PubChem CID: 313); Food industry and trade -- Periodicals; Food -- Composition -- Periodicals; Microbiology -- Periodicals; Nutrition -- Periodicals; 664.005
• DOI: 10.1016/j.lwt.2015.11.062
• Languages: English
• ISSNs: 0023-6438

Abstract

Abstract: General markers of HOCl induced changes in food proteins were evaluated and compared with the specific indicator 3-chlorotyrosine using dairy proteins at various oxidant/protein ratios and at different pHs. Protein aggregation was more pronounced at alkaline pH and already observed at a ratio of 0.3 mmol HOCl/g protein. Tryptophan, methionine, tyrosine and lysine in whey proteins showed more degradation at pH 8.0, whereas methionine and histidine in caseins were more vulnerable for degradation at pH 5.8. Total thiol content was strongly decreased, up to 75% at 4.8 mmol HOCl/g whey protein with more degradation at acidic pH while in caseins it remained constant. The available lysine content notably decreased upon HOCl treatment and was more pronounced at pH 8.0. The levels of 3-chlorotyrosine increased as function of the oxidant/protein ratio and reached a maximum at 2.8 mmol HOCl/g whey and casein proteins. The 3-chlorotyrosine concentration was observed the least at pH 8.0, while the increase in protein carbonyls depended only on the HOCl/protein ratio, but not on the pH. It is concluded that 3-chlorotyrosine provides a more accurate assessment of the impact of HOCl damage on proteins in foods. Highlights: The carbonyl content significantly increased upon HOCl oxidation. Lys, Tyr, Trp and Met were the most sensitive sites of oxidation within proteins. HOCl induced molecular changed proved to be pH dependent. Protein carbonyls for both proteins and SH groups (of caseins) were pH independent. 3-chlorotyrosine is a potential marker for HOCl induced damage in food proteins.