Abstract: In order to study the correlation between emulsion properties and microencapsulation rates and surface oil contents under different homogenization and sterilization conditions, the effects of emulsion stability, particle size, and particle size distribution on microencapsulation efficiency under different conditions were measured using a LUMiSizer 611 dispersion analyzer, and the morphological properties and storage stability of microcapsules under optimal conditions were analyzed. The results showed that the homogenization pressure and temperature and the sterilization conditions that provided the smallest emulsion stability index and average particle size were 40 MPa, 65 ℃ and 85 ℃/15 min, respectively. Under these conditions, particle size distribution was less scattered, and encapsulation rates of 95.38%, 97.12% and 94.23% were obtained, respectively. The average particle size of walnut oil microcapsules was 6.62 μm, with a surface oil content of 1.03% and an encapsulation rate of 96.41%. The surface and internal structure of the microcapsules were found to be good by scanning electron microscopy (SEM) indicating good encapsulation efficiency. Under accelerated storage conditions, walnut oil microcapsules showed better stability than free walnut oil. After 35 days of storage under different conditions, the reduction in the retention rate of walnut oil microcapsules varied, and the highest retention rate was achieved under the conditions of low temperature, darkness, and no oxygen or low oxygen concentration. This study could provide a theoretical basis for the selection and application of homogenization and sterilization processes for walnut oil emulsion and microcapsule products.

Key words: walnut oil; homogenization conditions; sterilization conditions; particle size; encapsulation rate; stability