Combined membrane filtration and alcohol-precipitation of alkaline soluble polysaccharides from sugar beet pulp: Comparision of compositional, macromolecular, and emulsifying properties

Alkaline soluble polysaccharide 1 (ASP1) was a polysaccharide extracted from residues remaining from the extraction of sugar beet pulp. This study aimed to separate ASP1 into five different fractions, named UP, UR, F50, F65 and F75, by using ultrafiltration membrane and stepwise alcohol-precipitation. The results showed that the fractions differed from each other regarding their chemical and macromolecular features. The Mw of these subfractions decreased in the order of F65 (340 kg mol(-1)), UR (325 kg mol(-1)), F75 (295 kg mol(-1)), F50 (278 kg mol(-)(1)) and UP (78 kg mol(-1)). The emulsifying properties of these fractions in oil-in-water systems containing 10% w/w MCT were compared, taking ASP1 as the reference. At concentrations of 1% of each polysaccharide, F75 showed the best emulsifying activity with the d(4,3) value of 0.35 mu m, while the droplet size for UP was 10 times greater than the others. After storage at 60 degrees C for seven days, emulsion stability decreased in the order of F65, UR, ASP1, F75, F50 and UP, based on the d(4,3) value increment of 0.27 mu m, 0.95 mu m, 1.48 mu m, 3.33 mu m, 3.99 mu m and 21.5 mu m, respectively. Due to the occurrence of calcium bridge flocculation, most polysaccharides in this work could not stabilize oil-inwater systems into homogeneous emulsions, except F65 and F75, in which d(4)(,3) values were increased from 1.22 and 0.72 mu m to 13.7 and 3.6 mu m, respectively, after storage, demonstrating great resistance to calcium for F75. In conclusion, membrane filtration combined with alcohol-precipitation is feasible to separate the mother polysaccharide into sub-fractions with different emulsifying properties, among which selected fractions exhibiting superior emulsifying properties could be used as potential emulsifiers in low-calcium systems.