A novel hydrochloride-free chitosan oligosaccharide production method to improve taste

Chitosan oligosaccharide hydrochloride (COS-HCl) has an unpleasant taste. To improve this taste, we used an enzymatic hydrolysis with chitosan to manufacture hydrochloride-free chitosan oligosaccharide (HFCOS). We found that HFCOS powder with weight-average molecular weight (Mw) of approximately 1000 and a high degree of deacetylation can be obtained from amorphous chitosan in carbonated water by enzymatic hydrolysis because amorphous chitosan slightly dissolves in carbonated water. HFCOS was stable enough to be atomized by spray-drying. However, HFCOS yield was quite low (15.7%). There were few chloride ions in HFCOS (0.1% ± 0.1%), in contrast to the number of chloride ions in COS-HCl (16.6% ± 0.6%) with statistical significance (p < 0.01). The molar ratio of anion/amino group of HFCOS was only 0.05. Therefore, it appeared that the amino groups of HFCOS were mostly free bases. In sensory evaluations, 5% w/w HFCOS was significantly sweeter than 5% w/w COS-HCl (p < 0.01); saltiness, acidity, bitterness were significantly weak (p < 0.01); and aftertaste and overall taste were significantly improved (p < 0.01). These results suggest that HFCOS can be obtained by a novel method of enzymatically hydrolyzing amorphous chitosan dissolved in carbonated water and this is one way to improve its taste.