Formation of dry beads for bioactives encapsulation by freeze granulation
Mackenzie M. Hansen, Richard W. Hartel, Yrjö H. Roos
Abstract
Solid beads formed by whey protein isolate (WPI) and various sugars/polyols with a wide range of glass transition temperatures showed potential as structures for encapsulation of Aronia berry bioactives. Whey protein isolate (WPI), Aronia extract, and carbohydrates (maltitol, sucrose, or trehalose) were mixed into water to form concentrated liquid feed dispersions with varied pH. Microstructures were imaged and physical properties including complex viscosities, surface tensions, particle size distributions, and centrifuge separation were measured to investigate the effects of carbohydrate type, WPI:sugar ratio, and Aronia polyphenols (PP) concentration on liquid properties. Feed dispersions were used to produce dry beads with an adapted freeze granulation method, where individual drops were pumped into liquid nitrogen for flash freezing and harvested for subsequent freeze-drying to remove water. Dry bead diameters, water contents, and water activities were measured prior to measuring hardness and glass transition temperatures. While formulating with different sugars did not meaningfully impact liquid feed characteristics that impact processing, compositional differences were found to influence characteristics of the final dried beads more notably.