High intensity ultrasound assisted heating to improve solubility, antioxidant and antibacterial properties of chitosan-fructose Maillard reaction products

•High intensity ultrasound assisted (UA) heating improved chitosan-fructose Maillard reaction.•UA heating increased solubility and antioxidant activity of Maillard reaction products (MRPs).•Structural and thermal properties of MRPs were characterized.•UA Maillard reaction conditions were statistically optimized.

This study investigated chitosan-fructose Maillard reaction (MR) induced by high intensity ultrasound-assisted (UA) water-bath heating at 80 °C in a model system consisting of 1% chitosan and 0.5, 1 or 1.5% fructose solution (FS). Based on the yield of Maillard reaction products (MRPs), the optimal UA heating conditions were 7, 5 and 8 h for 0.5, 1 and 1.5% FS, respectively, whereas they were 7, 8, and 7 h for 0.5, 1 and 1.5% FS, respectively for water-bath heating alone. Under the optimal conditions, the solubility of MRPs produced by UA heating reached 8.35-9.65 g/L versus 5.32-7.37 g/L without UA heating. The yield of MRPs from UA heating and water-bath heating alone was 12.45-18.86% and 5.78-10.02%, respectively. Reducing power (0.40-0.65), DPPH free radical scavenging capacity (79.71-98.70%) and ORAC (533.30-1218.62 μmol TE/L) of MR solutions from UA heating were higher than those from water-bath heating alone. MRPs showed higher antibacterial activity against Staphylococcus aureus (MIC of 2500 mg/L) and Escherichia coli (MIC of ∼313-625 mg/L) than that of native chitosan, but no difference was found in MRPs from water-bath heating alone. This study suggested that the high intensity UA water-bath heating could produce water soluble chitosan-fructose MRPs with significantly improved functionality.