Effect of feed liquid temperature on the structural morphologies of d-limonene microencapsulated powder and its...

The influence of the feed liquid temperature of the spray drying was investigated on the particle morphology (vacuole size and shell thickness of hollow particle) and the stability of encapsulated d-limonene. The feed liquid was the mixture of d-limonene emulsified in a wall material of blending gum arabic (GA) and maltodextrin (MD) at the mass ratio of 1 : 2, and the liquid temperature was varied from 40 to 80 degrees C. The percentage of the hollow particle in the spray-dried powder was over 40% and slightly increased with the rising of the feed temperature. Hollow particles have shells of different thickness, which was estimated from the image with a confocal laser scanning microscope (CLSM). The shell thickness increased with the increase in the feed temperature. This finding was qualitatively supported by scanning electron microscopy (SEM) images of the fractured particles. In addition, release and oxidation stability of encapsulated d-limonene were measured at constant temperature and humidity. The powder at high temperature of feed has higher stability for release and oxidation of d-limonene than that at a lower feed temperature. The result may partly be attributed to the increase of the shell thickness of the particle at a higher feed temperature. The thicker shell wall possibly served as the barrier of the flavor release and the diffusion of oxygen and moisture from the surrounding environment.