Spray-dryer feed preparation: Enzymatic degradation of glucomannan for iron nanoencapsulation

Abstract

Viscosity of glucomannan (GM) needs to be modified to support its application for spray drying encapsulation. The purpose of this study was to investigate degradation of GM using cellulase that fulfills viscosity in a spray-dryer specification. This hydrolyzed glucomannan (HGM) was subsequently spray-dried for encapsulating iron. Lower initial GM concentrations (0.5–1%) reached approximately 0.30 Pa·s which allowed to be spray-dried after 100 min degradation using 10 mg/L cellulase. Meanwhile, viscosity of 1.5% and 1.7% GM did not reach the target viscosity even after 300 min. The nth-order model was the most suitable model to achieve viscosity reduction of ≤1.5% initial GM concentration (coefficient of determination, R2 > 0.98), whereas the Mahammad model fitted the viscosity reduction of 1.75% initial GM concentration (R2 = 0.99). Hydrolysis decreased the degree of polymerization and surface tension but increased the antioxidant activities. Smaller molecules of the polysaccharides were released after hydrolysis. Particles of encapsulated iron using HGM were more hydrophilic than that using GM. The iron tended to have a higher release rate at pH 6.8 than at pH 1.2 in the first 40 min. Hence, the HGM showed its ability to act as a control release matrix for the iron that needs a protection in the acid environment, and delivers them to the neutral site for absorption. Nanoencapsulation using 0.35 Pa·s viscosity of HGM was able to have 84% yield, 96.41% encapsulation efficiency, and 10% moisture content. Particle size of the iron encapsulation was dominated by 68.62 nm-diameter. This study shows a potency to use an appropriate viscosity of HGM which not only allows to be spray-dried but also support in protecting the iron as aimed by encapsulation the iron. Performances and properties of this matrix on encapsulating other bioactive compounds become future study.