Abstract: In this study,Jiangyong Citrus grandis (grapefruit),one of the regional characteristics of Jiangyong Wuxiang,were used as raw material for the extraction of polysaccharides. Polysaccharides in peels of C.grandis was extracted with the ultrasonic-assisted hot water extraction method.The influencing factors,including solid/liquid ratio,ultrasonic treatment time,extraction temperature and time,were optimized through response surface analysis tests on the basis of single factor experiment.The results showed that the optimal extraction conditions were solid/liquid ratio of 1:25,ultrasonic treatment time of 3.8 min,extraction temperature of 70 ℃ and extracting for 2.6 h.Under the optimal conditions,the average extraction yield of polysaccharides was about 5.629%.Compared with the conventional hot water and alcohol precipitation method,the ultrasonic assisted extraction used less energy and had higher extraction efficiency.Hence,it was concluded that the ultrasonic assisted extraction method can be used as an effective method for the extraction of polysaccharide from peels of C.grandis.

Key words: Citrus grandis, polysaccharides, extraction, response surface methodology