Abstract:

Chitosan cross-linked with 2,5-bis(formic acid)-3,4-diolthiophene(DTCC) was prepared with ethyl chloroacetate, sodium sulfide, diethyl oxalate and chitosan(CTS) as raw materials. The antibacterial effect of cross-linked polymer was studied against a series of test bacterial cultures by quantitative suspension method. Relation between storage time and variation of white peach mass-loss ratio, decomposition ratio, chlorophyll content, film penetration ratio and total saccharine content was examined thoroughly after fresh-keeping process with synthesized cross-linked polymer as over-coat film. Results obtained from experiments indicated that partially cross-linked DTCC had a relatively strong antibacterial effect against Gram-positive and Gram-negative bacteria. The mean anti-bacterial ratios of DTCC for pseudomonas aeruginosa(MSH), pseudomonas fluorescens(ATCC13525), bacillus cereus(CIP6624), bacillus subtilis(ATCC6633) are 96.7％,95.8％,97.9％and 98.2％, respectively, after 20 min treatment. The minimal inhibited concentrations(MIC) for 4 bacteia are 25.0, 25.0, 3.1 and 3.1 g/L, respectively. DTCC also demonstrates strong antibacterial effect on aspergillus niger and penicillium italium: mean antibacterial ratios for above bacteria are 99.0％ and 28.4％, respectively, with corresponding MIC of 25.0 and 12.5 g/L after 20 min treatment. DTCC with concentration of 1.0 g/L coated on the outer skin of white peaches shows a good preservation effect after 12 d storage under (27±0.5) ℃. The mass-loss, decomposition and film penetration ratios are 8.1%, 40% and 34.1％, respectively. The total saccharine content is around 75.1 mg/g.

Key words: Chitosan, chitosan cross-linked with bis(formic acid)diolthiophene, fresh-keeping, Antibacterial effect