Effect of sulphydryl reagents on the heat stability of whey protein isolate

• Published in: Food chemistry 2014-11, Vol.163, p.129-135
• Main Authors: Wijayanti, Heni B., Bansal, Nidhi, Sharma, Ranjan, Deeth, Hilton C.
• Format: Article
• Language: English
• Subjects: Aggregation; Biological and medical sciences; Chromatography, High Pressure Liquid; Dihydrolipoic acid; Food toxicology; Heat stability; Hot Temperature; Lactalbumin - chemistry; Medical sciences; Milk Proteins - chemistry; Protein Stability; Sulfhydryl Reagents - pharmacology; Sulphydryl reagents; Toxicology; Whey protein isolate; Whey Proteins; α-Lactalbumin; β-Lactoglobulin
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2014.04.094

•Dihydrolipoic acid (DHLA) improved the heat stability of β-lactoglobulin in WPI.•DHLA and glutathione (GSH) reduced the heat stability of α-lactalbumin (α-La).•DHLA and GSH were reactive towards a disulphide bond of α-La.•DTNB and NEM were not reactive towards a disulphide bond of α-La.•N-ethylmaleimide improved the heat stability of all whey proteins in WPI. The effects of sulphydryl (–SH) reagents on protein aggregation reactions in heated whey protein isolate (WPI) and pure α-lactalbumin (α-La) were investigated. In contrast to its previously reported effect with pure β-Lg, dihydrolipoic acid (DHLA) markedly reduced the heat stability of WPI, especially the α-La component, which aggregated much more readily in the presence of DHLA than in WPI alone. Whilst pure α-La is quite stable to heat, it is much less stable in the presence of DHLA. An effect similar to DHLA was observed with reduced glutathione (GSH). N-ethylmaleimide (NEM), and to a lesser extent, dithio(bis)-p-nitrobenzoate (DTNB), improved the heat stability of WPI; these reagents had little effect on α-La.