羧甲基香豆胶的制备与表征

Preparation and Characterization of Carboxymethyl Fenugreek Gum

通过加入NaOH与一氯乙酸钠(SMCA)固体进行香豆胶(FG)的碱化和醚化,制备了不同取代度的羧甲基香豆胶(CMFG)。研究了不同分散介质、反应温度与时间、NaOH与SMCA用量等因素对取代度与反应效率的影响。以异丙醇/水为分散介质,产物取代度与反应效率最大,优化的反应温度为50℃、反应时间5h、醇水体积比52.5∶7.5。醇水体积比为50∶10、n(SMCA)∶n(NaOH)∶n(FG)=1∶1∶1时取代度为0.75,反应效率达75%。NaOH对取代度的影响大于SMCA。采用一步羧甲基化反应制备取代度1.05的CMFG,反应效率可达到70%。CMFG溶液黏度随取代度增大而增大,w(CMFG)=2%时,取代度为0.78,溶液黏度为116mPa.s。CMFG水溶液黏度4d降低8.6%～28.0%,黏度稳定性高于在w(NaCl)=1%的盐水溶液中的稳定性。

Carboxymethyl fenugreek gum （CMFG） with different degree of substitution （DS） was synthesized with NaOH and sodium monochloroacetate （SMCA） powder as the basifying and etherifying agents. The highest DS and reaction efficiency（RE） are obtained by applying the mixture of isopropyl alcohol and water as reaction medium. The optimum conditions are temperature 50 ℃ ,time 5 h and V （ isopropyl alcohol） ： V（ H2O） = 52.5：7.5. Under the conditions of V（ isopropyl alcohol） ： V（ H2O） = 50 ： 10 and n （SMCA） ：n （NaOH） ： n（FG） = 1 ： 1 ： 1, DS is 0.75 with a RE of 75 %. The NaOH content has greater effect on the DS and RE than that of SMCA. The DS of 1.05 can be obtained in one - step carboxymethylation with a RE of 70%. The viscosity of CMFG aqueous solution increases with increase in DS. As for CMFG with a DS of 0.78, the viscosity of aqueous solution with 2% CMFG is 116 mPa· s. The viscosity decreases by 8.6% - 28.0% within four days and is more stable than that of brine solution with 1% NaCl.