The effect of processing conditions on the formation and properties of a soft, food-based nanoparticle delivery system
Soft, food-based nanoparticles formed from amylose, ?-lactoglobulin, and linoleic acid have documented ability to encapsulate sparingly soluble, small molecules with potential to act as a food delivery system. The current study focused on gaining a better understanding of nanoparticle formation and the effects of processing parameters on the nanoparticle characteristics to aid in process scale-up. The formation of the nanoparticles was monitored using rheological and physicochemical methods (e.g. chromatography, dynamic laser scattering, microscopy). Using rheology it was found that nanoparticle formation was not responsible for the characteristic cooling stage viscosity peak, and that these particles form earlier during processing. Oscillatory rheology determined that particles processed at 1?C/min form between zero and 74 seconds after the addition of linoleic acid to the system and that neither cooling nor heating was required for nanoparticle formation. Particles were formed at temperatures as low as 25?C as verified with high performance size exclusion chromatography and transmission electron microscopy. The observed characteristic cooling stage viscosity peak was instead hypothesized to be a property of leached, un-complexed amylose undergoing retrogradation and variations in the heating stage viscosity profile were attributed to differences in processing rates and the result of nanoparticle formation and starch granule swelling. It was found that nanoparticle shape was not significantly affected by processing conditions. Processing time did not have an effect on particle yield or equivalent size but temperature cycling resulted in greater yield and smaller particles, though this appeared to be rate dependent. An overall hypothesis was developed based on availability of amylose in the system including a potential formation mechanism with two possible steps. The first step occurs after the addition of linoleic acid and is the rapid formation of nanoparticles from available amylose in the system. The second step is dependent on the rate of processing to determine whether, and the extent to which, more amylose is made available to form more complexes.
Hamaker, Purdue University.
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