Journal Articles

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    Whey protein nanofibrils: kinetic, rheological and morphological effects of group IA and IIA cations
    (International Dairy Journal, 2012) Loveday, SM; Su, Jiahong; Rao, M. Anandha; Anema, Skelte G.; Singh, Harjinder
    Self-assembly of whey proteins into amyloid-like fibrils during heating at pH 2 and low ionic strength is sensitive to the presence of NaCl and CaCl2. Our earlier work established that at 10 - 120 mM of these salts speeds up self-assembly and favours short, flexible fibrils over long semiflexible fibrils in a way that depends on cation concentration and cation type. Here we explored how other mono- and divalent salts affected fibril morphology and the rheology of fibril dispersions. Divalent salts (MgCl2, CaCl2, BaCl2) had much stronger effects than monovalent salts (LiCl, NaCl, KCl) on gelation kinetics, and differences between salts of the same type were not large. No marked effects of salt type on fibril morphology were evident, but there were subtle differences in the size and extent of fibril networks with mono- vs. divalent salts, which may explain differences in bulk rheology.
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    β-Lactoglobulin nanofibrils: Effect of temperature on fibril formation kinetics, fibril morphology and the rheological properties of fibril dispersions
    (Elsevier Ltd, 2012-05) Loveday SM; Wang XL; Rao MA; Anema SG; Singh H
    Almost all published studies of heat-induced b-lactoglobulin self-assembly into amyloid-like fibrils at low pH and low ionic strength have involved heating at 80 C, and the effect of heating temperature on self-assembly has received little attention. Here we heated b-lactoglobulin at pH 2 and 75 C, 80 C, 90 C, 100 C, 110 C or 120 C and investigated the kinetics of self-assembly (using Thioflavin T fluorescence), the morphology of fibrils, and the rheological properties of fibril dispersions. Self-assembly occurred at all temperatures tested. Thioflavin T fluorescence increased sigmoidally at all temperatures, however it decreased sharply with >3.3 h heating at 110 C and with >5 h heating at 120 C. The sharp decreases were attributed partly to local gelation, but destruction of fibrils may have occurred at 120 C. Thioflavin T fluorescence results indicated that maximal rates of fibril formation increased with increasing temperature, especially above 100 C, but fibril yield (maximum Thioflavin T fluorescence) was not affected by temperature. At 100 C and 110 C, fibrils were slightly shorter than at 80 C, but otherwise they looked very similar. Fibrils made by heating at 120 C for 1 h were also similar, but heating at 120 C for 8 h gave predominantly short fibrils, apparently the products of larger fibrils fragmenting. Heating at 100 C gave consistently higher viscosity than at 80 C, and heating for >2 h at 120 C decreased viscosity, which may have been linked with fibril fragmentation seen in micrographs.