In recent years, pectin is suggested to possess various pharmaceutical activities including wound healing ,lipase inhibition, apoptosis induction of human cancer cell, as well as immunostimulating, anti-metastasis, anti-ulcer, cholesterol decreasing effects, etc. Grapefruit peel pectin which has short side chains is rich in rhamnogalacturonan I backbones in particular compared with orange, lime and lemon, possessing potential values in bioactivity. However, unmodified pectin is thought to be too large to be absorbed in the body while modified pectin that has been broken down into smaller fragments can be absorbed more easily. It is noteworthy that high intensity (>10 W/cm2) power ultrasound is proved to be an effective tool to improve the bioactivities via modifying the molecular properties of polysaccharides . Therefore, it could be envisaged that high intensity UAHE had the potential to simultaneously achieve the high-efficient extraction and modification/preliminary modification of pectin. From this point of view, it is of great importance to promote further studies and applications in pectin extraction using this innovative method. To reduce the degradation effect of ultrasound, output power intensity of ultrasound was commonly kept at a low level (1–8 W/cm2) when it was used in the extraction of polysaccharides. Therefore, the effect of ultrasound intensity on the yield of pectin is scarcely studied. In a previous study (Xu et al., 2014), we reported that the
mechanism of high intensity (>10 W/cm2) ultrasound enhanced pectin yield was improving pectin extractability through disrupting vegetal tissue. It could be seen that ultrasound intensity had
significant effects on pectin extraction. Besides, extraction temperature and sonication time were also essential variables of UAHE. However, few works has been performed in the optimization of UAHE conditions and exploration of the combined effects of these variables in the process of
pectin extraction. In the current study, response surface methodology (RSM) was employed to study the extraction of grapefruit peel pectin using UAHE, aiming at optimizing the conditions for the extraction of pectin from grapefruit peel, as well as understanding the combined
effects of key operating variables (output power intensity of ultrasound, extraction temperature and sonication time) on the yield of pectin. In addition, comparative analysis of extraction yield, molecular structure, and physico-chemical properties of pectin extracted
by UAHE and CHE were also investigated.