ABSTRACT
The development of a new manufacturing process, a two-step temperature treatment, to modulate the physicochemical properties of nanoparticles including the size is critical. This is because its physicochemical properties can be key factors affecting the cellular uptake and the bioavailability of bioactive compounds encapsulated in nanoparticles. The aims of this study were to produce (beta-lactoglobulin) ß-lg nanoparticles and to understand how two-step temperature treatment could affect the formation and physicochemical properties of ß-lg nanoparticles. The morphological and physicochemical properties of ß-lg nanoparticles were determined using atomic force microscopy and a particle size analyzer, respectively. Circular dichroism spectroscopy was used to investigate the secondary structure of ß-lg. The surface hydrophobicity and free thiol groups of ß-lg were increased with a decrease in sub-ambient temperature and an increase in mild heat temperature. As sub-ambient temperature was decreased, a decrease in α-helical content and an increase in ß-sheet content were observed. The two-step temperature treatment firstly involved a sub-ambient temperature treatment from 5 to 20°C for 30 min, followed secondly by a mild heat temperature treatment from 55 to 75°C for 10 min. This resulted in the production of spherically-shaped particles with a size ranging from 61 to 214 nm. Two-way ANOVA exhibited the finding that both sub-ambient and mild heat temperature significantly (p<0.0001) affected the size of nanoparticles. Zeta-potential values of ß-lg nanoparticles were reduced with increasing mild heat temperature. In conclusion, two-step temperature treatment was shown to play an important role in the manufacturing process - both due to its inducement of the conformational changes of ß-lg during nanoparticle formation, and due to its modulation of the physicochemical properties of ß-lg nanoparticles.