Antimicrobial Activity of Chitosan Films With Essential Oils Against Listeria monocytogenes on Cabbage

BACKGROUND: The highest incidence of listeriosis, due to consumption of ready-to-eat foods and fresh, shredded, minimally processed vegetables, occurs among pregnant women and the elderly. In order to reduce the prevalence of listeriosis among consumers, better protective measures are recommended. Chitosan films, with or without added essential oils, represent a modern, safe method of preserving the quality of such vegetables and significantly reducing the incidence of Listeria monocytogenes in these foods. OBJECTIVES: The present study was conducted to evaluate the antimicrobial properties of composite chitosan-gelatin films with and without essential oils against two strains of L. monocytogenes, ATCC 19115 and ATCC 19112, in fresh shredded cabbage. METHODS: Shredded cabbage was inoculated with L. monocytogenes and packed between two layers of the chitosan composite film, then placed in Petri dishes. The prepared samples were stored at 4°C then analyzed for total viable count on PALCAM agar while incubated at 37°C, every 24 hours for 7 days. RESULTS: Average L. monocytogenes content ranged from 4.2 - 5.4 log CFU/g, reaching values of 7.2 - 8.6 log CFU/g in samples of untreated cabbage. A complete reduction of L. monocytogenes ATCC 19115 on cabbage was achieved after 120 hours in the presence of 0.5% chitosan film, whereas reduction of L. monocytogenes ATCC 19112 was achieved after 144 hours. In the presence of 1% chitosan film, the bacteria withered more quickly and complete reduction of both species of L. monocytogenes was achieved after 96 hours. CONCLUSIONS: All tested formulations of chitosan films exhibited strong antimicrobial activity on the growth of both strains of L. monocytogenes on cabbage. The best effect was achieved with a 1% chitosan concentration. The addition of essential oils increased the antimicrobial activity of all tested films

Development of tri-component antibacterial hybrid fibres for potential use in wound care.

Tri-component antibacterial psyllium-alginate-chitosan fibres were developed and their properties were studied with reference to their application in health-care. Psyllium was co-extruded with sodium alginate as a carrier into a coagulation bath containing calcium chloride and hydrolysed chitosan. Different concentrations of the hydrolysed chitosan were used and an in vitro assessment of antibacterial activity of the produced fibres was carried out against the known pathogens of Staphylococcus aureus and Escherichia coli. The effect of hydrolysed chitosan bath composition on physical and mechanical properties of produced fibres was also examined. Chitosan-containing fibres demonstrated a 70-130% thicker dry diameter than the control fibre (F1). The linear density of the fibre increased from 6.8 to 10 tex as the chitosan concentration increased from 10g/l to 30g/l (fibre type F1 to F4). With the addition of hydrolysed chitosan, distilled water absorption was increased while the saline and solution-A (0.83% w/v NaCl and 0.03% w/v CaCl ) absorption decreased. The percentage strain of hybrid fibres was lower than the control fibre due to the inclusion of hydrolysed chitosan. At lower viscosities of the hydrolysed chitosan bath, the fibres were much stiffer due to better penetration of the hydrolysed chitosan. Similarly, at lower viscosities, the tenacities of the hybrid fibres were higher than the control fibre. The hydrolysed chitosan-treated fibres were more effective against Staphylococcus aureus than the Escherichia coli, and the antibacterial activity increased with the decrease in viscosity of the hydrolysed chitosan bath. We developed novel PAC fibres. Antibacterial testing showed that hydrolysed chitosan was more effective against Gram-positive bacteria than Gram-negative bacteria