Conformational changes of β-lactoglobulin induced by shear, heat, and pH-Effects on antigenicity.
Structural modifications influence the immune-reactivity of food proteins. We investigated effects of pH (3, 5, 7), temperature (80, 100, 120°C), and shear (100, 500, and 1,000 s(-1)) on conformational changes (monitored by surface hydrophobicity, total thiol content, Fourier transform infrared spectroscopy, and gel electrophoresis) and their relation to antigenicity (determined by indirect ELISA) of β-lactoglobulin (β-LG). Overall, heating at low pH (3) caused unfolding of proteins and fragmentation due to partial acid hydrolysis and thereby exposed β-strands that contributed to appearance of some hidden epitopes, resulting in higher antigenicity. Heating at pH 5 and 7 decreased the allergenic response due to covalently bonded molecular polymerization and aggregation, which destroyed or masked some epitopes. Shear alone had no effect on the antigenic response of β-LG but may have an effect in combination with pH or temperature. Overall, heating β-LG solutions to 120°C at pH 5 with shearing (100-1,000 s(-1)) resulted in minimal antigenicity. Structural modifications of β-LG via denaturation or disulfide- or thiol-mediated interactions can either enhance or decrease its antigenicity.
Advanced Food Systems Research Unit, College of Health and Biomedicine, Victoria University, Melbourne, VIC 8001, Australia.
Toheder
T
Rahaman
Advanced Food Systems Research Unit, College of Health and Biomedicine, Victoria University, Melbourne, VIC 8001, Australia.
Todor
T
Vasiljevic
Advanced Food Systems Research Unit, College of Health and Biomedicine, Victoria University, Melbourne, VIC 8001, Australia. Electronic address: lata.ramchandran@vu.edu.au.
Lata
L
Ramchandran
D004587:Electrophoresis, Agar Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007782:Lactoglobulins / Q000737:chemistry* / Q000276:immunology; D011487:Protein Conformation; D033081:Shear Strength; D017550:Spectroscopy, Fourier Transform Infrared; D013438:Sulfhydryl Compounds
D007782:Lactoglobulins; D013438:Sulfhydryl Compounds
antigenicity; conformation; heat; pH; shear