Inactivation of Listeria monocytogenes by Ultraviolet Energy

Abstract

Short-wave W-energy (100 p,W/cmZ) decreased the number of List&u monocytogenes on Tryptose Agar (TA) ca. seven orders of magnitude in 4 min. Age of culture (48 vs 24 hr) did not alter the sensitivity of Listeria to this W treatment. Increasing the intensity of irradiation (550 vs 100 pW/cm2) increased the rate at which L. monocytogenes was inactivated. Dry rather than moist cells of L. monocytogenes were most resistant to irradiation. In general, inactivation of Lisferiu with short-wave W-energy yielded sigmoidal survivor curves. The population of Listeria on TA plates was not affected with long-wave Wirradiation.

The kinetics of Bacillus subtilis spore inactivation on filter paper by u.v. light and u.v. light in combination with hydrogen peroxide

“…Jagger et al (1967), working with S. griseus, found no difference between the sensitivities of wet and dry spores. Yousef and Marth (1988) on the other hand, found wet cells of Listeria monocytogenes to be more u.v. resistant than dry cells.…”

“…Leaper maintained that spores on the surface of packaging materials were more likely to be in the dry state and therefore, presumably, more resistant to disinfection treatments. However, as the results of Yousef and Marth (1988) indicate, the wet cells of certain species can be more resistant than dry cells and therefore, it would seem prudent to assess the resistance of both wet and dry forms of an organism when evaluating u.v.-based disinfection treatments.…”

Effectiveness of two-sided UV-C treatments in inhibiting natural microflora and extending the shelf-life of minimally processed ‘Red Oak Leaf’ lettuce

“…A superficial postharvest treatment that can be an adjunct to refrigeration for preserving fruit and vegetables is the use of nonionizing, germicidal, artificial ultraviolet (UV-C) radiation (Maharaj et al, 1999). This treatment brings some benefits to the fresh cut industry as its use is approved by the code of Food and Drug Administration (FDA) in the USA (Rhim et al, 1999) on food products to control surface micro-organisms, does not leave a residue, and does not require extensive safety equipment (Yousef and Marth, 1988;Wong et al, 1998;Yaun et al, 2004). Several in vitro studies have demonstrated the efficiency of UV-C radiation on microbial inhibition (Gardner and Shama, 2000).…”

The use of products containing a phage in food industry as a new method for Listeria monocytogenes elimination from food (Listeria monocytogenes phages in food industry) - a review

“…The number of cells not forming a biofilm can be reduced by 4 orders of magnitude as a result of UV-C 275 nm radiation of 750 µW/min/cm 2 , whereas a reduction by 5 orders of magnitude has been reported as a result of the radiation beam of UV-C 254 nm at 100 µW/min/cm 2 . However, these results cannot be applied to biofilm-forming bacterial cells (Yousef & Marth 1988).…”