Tuning the properties of b-lactoglobulin nanofibrils with pH, NaCl and CaCl2

Abstract

We investigated the effects of pH (1.6 – 2.4), NaCl and CaCl2 (0 – 100mM) on the kinetics of β-lactoglobulin fibril formation during heating at 80°C. The morphology of fibrils was also examined. At pH 1.8 - 2.4 fibril formation occurred slightly faster with decreasing pH. At pH 1.6 fibril formation during the growth phase occurred much faster than at any other pH. Fibril morphology was unchanged between pH 1.6 and pH 2.0. Addition of NaCl or CaCl2 accelerated fibril formation during the growth phase, and CaCl2 shortened the lag phase as well. Worm-like fibrils were seen at ≥ 60 mM NaCl or ≥ 33 mM CaCl2, and these had a persistence length which was much shorter than the long semi-flexible fibrils formed without salts. The efficiency of fibril formation can be substantially enhanced by varying pH and salt concentration.