Browsing by Author "Liu, Lingdai"

The literature review introduced properties of native cellulose and common water-soluble cellulose derivatives, pathways to develop antimicrobial packaging from cellulosic materials, mechanisms of existing antimicrobial packaging systems and characterization of antimicrobial films. Special emphasis was given to potential of cellulose betainates (CB) as inherently antimicrobial, low-toxic materials for development of antimicrobial films. The aim of this study was to investigate overall potential of CB as antimicrobial films. CB together with commercial cationic starch (CS) and chitosan (CH) added with different amounts of sorbitol were prepared into films by solution casting. Mechanical properties, moisture and oxygen barrier attributes, and microscopic characteristics of aforementioned films were determined. In addition, antimicrobial potential of CB were tested against Listeria innocua and Escherichia coli compared to CS and CH by agar diffusion assay for films and measurements on optical density at 600nm for aqueous polysaccharide solutions. CB forms self-standing films with relatively low mechanical strength and stiffness while possessing good flexibility and medium barrier properties against water vapor and oxygen. CB films is antimicrobial against E. coli but not against L. innocua according to agar diffusion assay. Based on growth inhibition ratio (GIR%) from solution-phase tests, L. innocua was also more resistant than E. coli against CB at concentrations below 512 µg/ml. CB exhibited similar antimicrobial activity to that of CH within 512–1280 µg/ml. However, an increase in viscosity of CB solution at higher concentration (2560 µg/ml) as well as excessive microorganism (~108cfu/ml) in initial inoculum led to decrease in their antimicrobial efficacy. In conclusion, CB is antimicrobial against E. coli in film, and potential to exert similar antimicrobial potency as that of chitosan in solution with adequate quantities. Therefore, CB is a promising candidate as for fabrication of antimicrobial films. However, the antimicrobial mechanism, antimicrobial spectrum of CB and the applicability of CB films require further explorations.