Transglutaminase catalyzed hydrolyzed wheat gliadin grafted with chitosan oligosaccharide and its characterization

Chitosan oligosaccharide (COS) was grafted on hydrolyzed wheat gliadin (HWG) with microbial transglutaminase (MTGase) as catalyst. The grafting reaction exhibited the best performance when it was done under the optimum temperature 50 °C for 50 min with HWG/COS mass ratio of 40:1, pH 6.00-6.50. The maximum grafting rate of COS was 64.83% at this condition. The chemical structure characterizations of HWG-COS performed by FTIR, 13C NMR, X-ray diffractometry and TGA-DTG illustrated that amino groups in COS had participated in the formations of the amino band during the synthesis. HPLC and GFC analysis showed that HWG-COS had two main components, which together accounted for 80.64% of the total polymer and the molecular weight of the two components was 61.77 kDa and 27.29 kDa, respectively. HWG-COS was undissolved in water and many organic solvent, slightly soluble in 1% NaOH, with a solubility of 1.84 mg/L. In antibacterial activity test, HWG-COS showed the best antimicrobial properties to Salmonella enteriditis, with an antibacterial activity improved by 41.74%.