Inactivation of milk-borne pathogens by blue light exposure

Abstract

Food safety and quality management play a pivotal role in the dairy industry. Milk is a highly nutritious food that also provides an excellent medium for growth of pathogenic microorganisms. Thus, dairy industry focuses most of their processes and costs on keeping contamination levels as low as possible. Thermal processes for microbial decontamination may be effective; however, they cannot provide excellent organoleptic, nutritional, and decontamination properties simultaneously. In this scenario, microbial inactivation by exposure to blue light is a promising alternative method in the food industry due to its intrinsic antimicrobial properties free of any thermal effect. Therefore, this study aimed to determine the inactivation kinetics induced by blue light (λ = 413 nm) against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella Typhimurium, and Mycobacterium fortuitum cells suspended in whole milk or saline solution. We also performed a series of optic spectroscopies to investigate possible degradation of milk components. All species were sensitive to photoinactivation suspended either in saline solution or milk. Inactivation kinetics differs significantly depending on the suspension medium and each species is differently affected. All bacterial species tested presented more than 5 log 10 of inactivation within less than 2 h of irradiation (720 J/cm 2 ). Infrared spectroscopy did not reveal any significant alteration in any of the milk constituents (e.g., sugars, proteins, and lipids). Riboflavin (vitamin B 2 ) was the only sig-nificantly degraded constituent found. Therefore, we conclude that microbial inactivation performed by blue light presents extraordinary potential for processes in the dairy industry.

Management strategies emphasizing advanced food processing approaches to mitigate food borne zoonotic pathogens in food system

“…Dos Anjos et al. (2020) investigated the effect of blue light in milk on the inactivation of S. aureus, E. coli, P. aeruginosa, S. typhimurium , and Mycobacterium fortuitum and achieved an approximately 5 log reduction using 720 J/cm 2 for 2 h of treatment time. An in vitro study by Inagaki et al.…”

“…Consumption of unpasteurized milk, dairy‐based products, undercooked meat, poultry, sea food, and ground beef are potential sources of foodborne pathogens and risks of zoonosis to consumers. Sources of pathogens and their association with various diseases are listed in Table 2 (Chuang et al., 2020; Dos Anjos et al., 2020). Dairy‐based pathogens causing foodborne outbreaks in Europe were Salmonella spp., followed by Campylobacter spp.…”

Photodynamic inactivation effects on foodborne pathogens and its application in food products

“…Among them, riboflavin shows an absorption peak in the band width 400~500 nm [87]. By means of this property, dos Anjos et al (2020) [88] observed a >5 log unit inactivation of all bacterial species (S. aureus, E. coli, P. aeruginosa, S. typhimurium, and M. fortuitum) within 2-h irradiation. Analysis of sugars, proteins, and lipids showed no evident degradation of milk components except for riboflavin, and this defect could be corrected by supplementation.…”

“…The use of photodynamic technology to decontaminate food packaging materials has been widely reported [56,60]. Eukaryotic cells are far less sensitive to blue light than are bacterial cells [88], which indicates that the technique can be popularized as an alternative sterilization method still in an infancy stage. There is vast research and development still needed to optimize this technology before it is routinely used within the food industry.…”

Enhanced Sensitivity of Salmonella to Antimicrobial Blue Light Caused by Inactivating rfaC Gene Involved in Lipopolysaccharide Biosynthesis

“…LED illumination (405 -5 nm) at 1.7 kJ/cm 2 decreased to 1.0-1.2 log CFU/cm 2 of four Salmonella enterica serovars in papaya (Kim et al, 2017). Besides, more than 5 log 10 of the population of Salmonella Typhimurium ATCC 14028 in milk was achieved by 413 nm aBL irradiation at a dose less than 720 J/cm 2 (Dos Anjos et al, 2019). However, as reviewed by Dai et al (2012), the bactericidal mechanism underlying aBL treatment is still not fully revealed.…”