Flocculation Effect And Mechanism Of Removing Pectin In Chinese Herbal Medicine Water-extract

The purification method of traditional Chinese medicine(TCM) in past was primarily alcohol precipitation, which owed some drawbacks such as long production period, high energy consumption and low retention rate of active constituents. Flocculation technology has attracted much attention in the field of TCM purification for its short production cycle, simple operation and well purifies effects. As Chinese medicine water-extract(CMWE) has complex components and diverse impurities, pectin, one of the typical impurities, was selected as the treatment target. The effects of flocculant type, flocculant dosage, the pectin concentration, pH value and the solution temperature on the flocculation efficiency of high and low methoxyl pectin were researched. Besides, the FTIR spectra of pectin and its flocs were analyzed to determine the flocculation mechanism. And then a flocculant which showed the best flocculation performance on pectin was chose to purify the “Xingsu cough syrup” water-extract, and the effects of flocculant dosage, pH and temperature on the flocculation efficiency were investigated based on the removal rate of pectin, supernatant turbidity and retention rate of active constituents.The results showed that the removal rate of high methoxyl pectin by Chitosan quaternary ammonium salt(HTCC) and chitosan hydrochloride, and low methoxyl pectin by HTCC and chitosan hydroxypropyl, firstly increased and then decreased with the increase of flocculant dosage, pectin concentration, pH value and solution temperature, while the variation tendency of supernatant turbidity was opposite. Meanwhile, the zeta potential of flocs kept rising from negative to positive with increase of the flocculant dosage. The hydrogen bonding, electrostatic adsorption and hydrophobic interaction between pectin and flocculants were considered to provide the adsorption affinity. Polymer bridging and charge neutralization played important role jointly in the flocculation process. Although these flocculants all had good flocculation capacity on removing pectin, HTCC showed better flocculation efficiency. The optimum flocculation operation condition for high and low methoxyl pectin with HTCC was: dosage 0.75 and 1.00g/L, pectin concentration 2.5g/L, pH value 3.5~4.0, solution temperature 50℃, and the pectin removal rate were 96.1% and 93.2%, supernatant turbidity were 6.3 and 4.2 NTU, respectively.In the flocculation experiment of “Xingsu cough syrup” water-extract by HTCC, the removal rate of pectin firstly increased and then decreased, while the variation tendency of supernatant turbidity was opposite, with the increase of flocculant dosage, pH value and solution temperature. The optimum operation condition was: dosage 0.9 g/L, pH value 3.5~4.0 and solution temperature 30~40℃, which the removal rate of pectin and supernatant turbidity were 78.2 and 9.8 NTU, and the retention rate of hesperidin was 95.48%. Thus, flocculation technology applied in TCM purification process under appropriate condition showed high flocculation selectivity and efficiency.