果胶甲酯化反应及应用高甲氧基果胶制备纳米乳液

Methoxylationof commercial citrus pectin in absolute methanol catalyzed byHCl was conducted. Reaction conditions including reaction time, temperature, solid-to-liquid ratio (SLR) and HClconcentration were investigated and optimized, to produce the high methoxyl pectin possessingvarious degree of methoxylation (DM)of 65%->90%. Results of molecular weight distribution showed that the DMwas improved with the increase of the reaction temperature, reaction time and acid concentration, but the number-average molecular weight was correspondingly decreased. Particularly, HMPwith DM of 91.20±0.13% was obtained underSLR 1:50(w/v) at 60℃with 0.12 M HCl for 12 h, and the Mw was decreased to 15.00 kDa. Furthermore, based on the extremely high DM (91.20%) generating amphiphilic (by hydrophobicmethoxyl groups andhydrophilichydroxyl groups) and the short molecular length, the emulsification properties of pectin were studied. Nano-emulsions (oil content 10%~30%, v/v) were prepared by high energy method (high speed shearing) and their 7-day stability, Zeta-potential and particle size was characterized. High methoxyl pectin with DM of 91.20% produced emulsion of about 3500 nmwith good stability.