Abstract: In this study, zein was grafted with glucose or xylose, and grafted zein/astaxanthin particles were prepared to study the impact of glycosylation on the encapsulation of astaxanthin. The percentages of glucose and xylose grafted onto zein were 2.59% and 2.53%, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) using Coomassie staining and Schiff staining proved the existence of glycoprotein. Circular dichroism results showed that the secondary structure of zein was changed as evidenced by a decrease of alpha-helix and an increase of beta-sheet and beta-turn, indicating partial protein unfolding. The field emission scanning electron microscopy and differential scanning calorimetry measurements showed that the formed zein/astaxanthin particles were hollow with astaxanthin well dispersed around. Compared to the untreated zein, the encapsulation efficiency of astaxanthin was increased by 10% in the grafted zein. After dissolving in ethanol solution for 12 h, the release rate of pure astaxanthin was 99.8%, while in the case of zein/astaxanthin, zein-glucose/astaxanthin, zein-xylose/astaxanthin particles, the release rates were 49.7%, 31.7% and 30.2%, respectively. The thermal stability of astaxanthin was significantly improved in these particles. After heating treatment, the loss rate of pure astaxanthin was 75.29%, while only 25% of encapsulated astaxanthin was lost.

Key words: zein, astaxanthin, glycosylation, encapsulation transportation