Effects of environmental factors on heat-induced [beta]-lactoglobulin fibril formation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology, Riddet Institute, Massey University, Palmerston North, New Zealand

Thumbnail Image
Open Access Location
Journal Title
Journal ISSN
Volume Title
Massey University
The Author
The heat-induced fibrillar aggregation of β-lactoglobulin was studied under various environmental conditions. The formation of β-lactoglobulin fibrils was monitored by Thioflavin T (ThT) fluorescence and their morphology was studied using transmission electron microscopy (TEM). Amyloid-like fibrils were formed under standard conditions (pH 2.0, 80°C and low ionic strength). The β-lactoglobulin fibrillation kinetics exhibited sigmoidal behaviour, and the two-step autocatalytic reaction model fitted ThT fluorescence data well. The studies of the individual effect of pH, temperature, NaCl, CaCl2 on β-lactoglobulin fibril formation showed that decreasing pH (2.4 - 1.6), increasing temperature (75 - 120°C) and increasing salt concentration (NaCl 0-100 mM; CaCl2 0-100 mM) accelerated the fibril formation process and altered the morphology of fibrils. The two-step autocatalytic reaction model did not fit the ThT fluorescence data well at higher temperature (>100°C) or at low pH (1.6). The effects of the four factors (pH, temperature, NaCl and CaCl2) on β-lactoglobulin fibril formation were studied by using a central composition design (CCD) experiment. Results showed that the four main and some of the non-linear effects were significant (95%) on fibril formation, including fibrillation time and the fibril yield. Taking all results together, it can be implied that β-lactoglobulin fibril formation can be promoted by choosing the external incubation conditions. This study is the first step towards the application of protein fibrils as texture-modifying ingredients in food systems.
Milk proteins, Denaturation, Beta-lactoglobulin, Amyloid fibril, Thioflavin T fluorescence, TEM, β-Lactoglobulin