AUTHOR=Pendyala Brahmaiah , Vashisht Pranav , Chen Fur-Chi , Sanchez Savannah E. , Comstock Bob , Omsland Anders , Patras Ankit 

TITLE=Evaluating the UV-C sensitivity of Coxiella burnetii in skim milk using a bench-scale collimated beam system and comparative thermal sensitivity study by high-temperature short-time pasteurization

JOURNAL=Frontiers in Food Science and Technology

VOLUME=Volume 3 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/food-science-and-technology/articles/10.3389/frfst.2023.1251069

DOI=10.3389/frfst.2023.1251069

ISSN=2674-1121

ABSTRACT=<p><bold>Introduction:</bold><italic>Coxiella burnetii</italic> is a zoonotic Gram-negative obligate intracellular bacterial pathogen and the causative agent of query (Q) fever in humans. Contamination of milk by <italic>C. burnetii</italic>, as a consequence of livestock infection, is a significant public health concern. Effective methods to inactivate <italic>C. burnetii</italic> in milk are a critical aspect of food safety. Implementation of non-thermal UV-C processing technologies in the dairy industry can effectively preserve the sensory and nutritional quality of raw milk products while ensuring their safety, making them a viable alternative to traditional high-temperature short-time (HTST) pasteurization methods.</p><p><bold>Methods:</bold> Optical light attenuation factors, such as the absorption, scattering, and reflection by skim milk (SM) were evaluated using a spectrophotometer. SM inoculated with an avirulent strain of <italic>C. burnetii</italic> was irradiated using a collimated beam device equipped with a low-pressure UV-C 254 nm lamp at doses from 0 to 12 mJ/cm<sup>2</sup>. Optical properties were considered for the evaluation of the delivered UV-C dose. The pasteurization treatment was conducted using a lab scale HTST pasteurizer (72°C/15 s). The verification studies were conducted using <italic>Escherichia coli</italic> ATCC 25922 inoculated in a phosphate buffer (transparent fluid) and humic acid (opaque fluid). <italic>Salmonella enterica</italic> serovar Muenchen ATCC BAA 1674 inoculated in SM was tested for its suitability as a surrogate for <italic>C. burnetii</italic>, a bacterium that requires specialized equipment and expertise for experimentation.</p><p><bold>Results and Discussion:</bold> Absorption, reduced scattering coefficient, and the reflectance of SM at 254 nm were measured as 19 ± 0.3/cm, 26 ± 0.5/cm, and 10.6%, respectively. The UV-C results showed a log-linear inactivation of <italic>C. burnetii</italic> in SM with the UV-C sensitivity (D<sub>10</sub>) value of 4.1 ± 0.04 mJ/cm<sup>2</sup>. The results of HTST pasteurization revealed that <italic>C. burnetii</italic> was heat-sensitive with a D value of 1.75 min. <italic>Salmonella</italic> Muenchen showed similar UV inactivation kinetics and is, thereby, suggested as a suitable surrogate to <italic>C. burnetii</italic> for the pilot-scale UV-C processing studies of SM.</p>