Ultrasound-assisted encapsulation of annatto seed oil: Whey protein isolate versus modified starch

摘要

The objective of this study was to compare the performance of whey protein isolate (WPI) and modified starch (SF) based on their surface properties as adsorbents in the oil-water interface aiming the encapsulation of the annatto seed oil by ultrasound-assisted emulsification. We also analyzed the influence of WPI and SF on technological quality of the microparticles formed from the respective emulsions by freeze-drying (FD) and spray-drying (SD). The effects of ultrasonication power and processing time were assessed by the droplet size of the dispersed phase and creaming stability. The finer emulsions obtained with the evaluated biopolymers were subjected to the FD and SD processes. The obtained microparticles were characterized with respect to moisture content, size distribution and average diameter, morphology, surface oil, entrapment efficiency, encapsulation efficiency, X-ray diffraction patterns and thermal stability. Ultrasound-assisted emulsification of the oil led to the formation of fine kinetically stable emulsions. Intensification of the ultrasonication process had no positive effects on reducing droplet size, demonstrating the existence of a physico-chemical limit imposed by the characteristics of WPI and SF. The FD and SD techniques resulted in different microparticle sizes and morphologies; however, the microparticles formed using both techniques exhibited an amorphous state. Micrographs obtained by confocal laser scanning microscopy (CLSM) demonstrated encapsulation of the oil in all of the treatments; however, the WPI-FD microparticles showed greater entrapment efficiency, while the SF-SD microparticles showed greater encapsulation efficiency. The type of biopolymer and method used to form the microparticles had no effect on thermal stability because both microparticles showed high stability to thermal degradation. (C) 2015 Elsevier Ltd. All rights reserved.