Abstract: The pomegranate polyphenol was extracted by the ultrasonic method, and the emulsification-crosslinking technique was used to prepare microspheres of pomegranate peel extracts. The effects of reaction conditions, i.e., chitosan deposit time, amount of sodium alginate, and emulsifier dosage on loading efficiency, were optimized by using response surface method. The results showed that under the optimal conditons, the yield of dry extract of pomegranate peel was 50.5% and the polyphenol content of the extract was 47.8%. The data of microspheres were fitted using binomial equation (r=0.994). The optimum preparation conditions were follows: sodium alginate concentration 0.98%, chitosan deposit time 2.56 h, emulsifier concentration 17.83%, curing time 5 h, amount of glutaraldehyde 1 mL. Under above conditions, the loading efficiency of microspheres was 12.19%. There was slight difference between the actual value and predicted value. Under optimal conditions, DPPH radical scavenging rate was 96.92%, and the bacterial inhibition diameters of Micrococcus tetragenus, Bacillus subtilis, Staphylococcus aureus were 2.70, 2.78 and 2.72 cm, respectively. Pomegranate peel extract and its microspheres, which were treated under 37 ℃ and relative humidity 75%, had the DPPH radical scavenging rates of 78.53% and 91.26%, respectively.

Key words: pomegranate peel extracts, microspheres, response surface method