Oxidative stability of physiologically functional oil microencapsulated by spray drying

Abstract

Edible oils with physiological functions, such as fish oil and krill oil, which contain polyunsaturated fatty acids (PUFAs), are highly unstable to heat and oxygen. One of the methods for improving the shelf life of these oils is microencapsulation of the oils through spray drying. This mini-review describes the effects of the surface–oil ratio, oil location within the microcapsules, and oil-droplet diameter on the oxidative stability of functional oils in microcapsules prepared through spray drying. The surface–oil ratio, s, can be expressed through the ratio of the average oil-droplet diameter to the average powder diameter, E, by s = 1 − (1 − 2E)³. Additionally, the effects of oil-droplet size and storage temperature on the stability of the encapsulated oil were examined using squalene as a model functional oil. The activation energy E_a of the squalene degradation rate constant of the Avrami equation can be correlated with the average oil-droplet diameter d_e. The release behavior of the microencapsulated flavors is also discussed because spray drying is also used for the microencapsulation of flavors. The flavor release rate constant of the Avrami equation is related to the oxygen diffusion coefficient of the wall material.

Keywords:

• Spray drying
• oxidative stability
• surface oil
• kinetics
• oil-droplet diameter

Disclosure statement

No potential competing interest is reported by the authors.

Additional information

Funding

This work was supported by Japan Society for the Promotion of Science.