Inactivation of Staphylococcus aureus in Milk Using Flow‐Through Pulsed UV‐Light Treatment System

Abstract

This study investigated the efficacy of pulsed UV-light for continuous-flow milk treatment for the inactivation of Staphylococcus aureus, a pathogenic microorganism frequently associated with milk safety concerns. Pulsed UV light is an emerging technology, which can be used for the inactivation of this pathogen in milk in a relatively short time. Pulsed UV light damages the DNA of the bacteria by forming thymine dimers that lead to bacterial death. The effect of sample distance from the quartz window of the UV-light source, number of passes, and flow rate was investigated. A response surface methodology was used for the design and analysis of experiments. Milk was treated at 5-, 8-, or 11-cm distance from a UV-light strobe at 20, 30, or 40 mL/min flow rate and treated up to 3 times by recirculation of milk to assess the effect of the number of passes on inactivation efficiency. Log10 reductions varied from 0.55- to 7.26-log10 CFU/mL. Complete inactivation was obtained in 2 cases and no growth was observed following an enrichment protocol. Predicted results were in agreement with the experimental data. Overall, this work demonstrates that pulsed UV-light has a potential for inactivation of milk pathogens.

Pulsed Light Treatments for Food Preservation. A Review

“…As what occurs with conventional continuous UV light, the main mechanism of microbial inactivation by PL is explained through the photochemical effect (Wang et al 2005), which consists in the formation of pyrimidine dimers in the DNA of bacteria, viruses, and other pathogens, thus preventing the cell from replicating (Rowan et al 1999). However, additional modes of inactivation such as photothermal and photophysical effects have been proposed (Wuytack et al 2003;Krishnamurthy et al 2007). Some authors have attributed the cell disruption to a photothermal effect caused by absorption of UV light when fluence, energy received by the sample, is excessive (Hiramoto 1984;Wekhof 2000;Wekhof et al 2001).…”

A Comparative Study of the Bactericidal Activity and Daily Disinfection Housekeeping Surfaces by a New Portable Pulsed UV Radiation Device

“…2 Actual decontamination of the environmental surfaces in the ward using pulsed UV radiation. Note: Pulsed UV was irradiated at a distance of shorter than 5 cm and a time longer than 5 s, and the radiation unit was also swung over the objects to avoid any shadowed areas lamp without mercury, and short leveled free radical production [5,15,24]. The exposure-surface compatibility test of this pulsed UV radiation revealed no apparent effects, and the nurses who used the device wore UV elimination goggles to protect their eyes, and UV-A and UV-B were not detected on the handle of the radiation unit.…”

UV-C treatment of soymilk in coiled tube UV reactors for inactivation of Escherichia coli W1485 and Bacillus cereus endospores

“…The culture obtained from growth in TSB was centrifuged (Beckman J2-M1, Schaumburg, IL, USA) at 12,000 rpm (17,400 × g) for 15 min at 4°C and the supernatant was discarded (Krishnamurthy, Demirci, & Irudayaraj, 2007). The pellet was immediately mixed with soymilk as described in section 2.6.…”