title: Reduction of Bacterial Pathogens and Potential Surrogates on the Surface of Almonds Using High-Intensity 405-Nanometer Light.
abstract: The disinfecting properties of high-intensity monochromatic blue light (MBL) were investigated against Escherichia coli O157:H7, Salmonella , and nonpathogenic bacteria inoculated onto the surface of almonds. MBL was generated from an array of narrow-band 405-nm light-emitting diodes. Almonds were inoculated with higher or lower levels (8 or 5 CFU/g) of pathogenic E. coli O157:H7 and Salmonella , as well as nonpathogenic E. coli K-12 and an avirulent strain of Salmonella Typhimurium, for evaluation as potential surrogates for their respective pathogens. Inoculated almonds were treated with MBL for 0, 1, 2, 4, 6, 8, and 10 min at a working distance of 7 cm. Simultaneous to treatment, cooling air was directed onto the almonds at a rate of 4 ft3/min (1.89 ×10-3m3/s), sourced through a container of dry ice. An infrared camera was used to monitor the temperature readings after each run. For E. coli K-12, reductions of up to 1.85 or 1.63 log CFU/g were seen for higher and lower inoculum levels, respectively; reductions up to 2.44 and 1.44 log CFU/g were seen for E. coli O157:H7 (higher and lower inoculation levels, respectively). Attenuated Salmonella was reduced by up to 0.54 and 0.97 log CFU/g, whereas pathogenic Salmonella was reduced by up to 0.70 and 0.55 log CFU/g (higher and lower inoculation levels, respectively). Inoculation level did not significantly impact minimum effective treatment times, which ranged from 1 to 4 min. Temperatures remained below ambient throughout treatment, indicating that MBL is a nonthermal antimicrobial process. The nonpathogenic strains of E. coli and Salmonella each responded to MBL in a comparable manner to their pathogenic counterparts. These results suggest that these nonpathogenic strains may be useful in experiments with MBL in which a surrogate is required, and that MBL warrants further investigation as a potential antimicrobial treatment for low-moisture foods.
authors.affiliation: National College of Natural Medicine, 014 Southeast Porter Street, Portland, Oregon 97201.
authors.forename: Alison
authors.initials: A
authors.lastname: Lacombe
authors.affiliation: Food Safety and Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA.
authors.forename: Brendan A
authors.initials: BA
authors.lastname: Niemira
authors.affiliation: Food Safety and Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Sites
authors.affiliation: Food Safety and Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA.
authors.forename: Glenn
authors.initials: G
authors.lastname: Boyd
authors.affiliation: Food Safety and Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA.
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Gurtler
authors.affiliation: Food Safety and Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA.
authors.forename: Breanna
authors.initials: B
authors.lastname: Tyrell
authors.affiliation: Food Safety and Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Fleck
mesh_terms: D015169:Colony Count, Microbial; D019453:Escherichia coli O157; D005511:Food Handling; D005516:Food Microbiology; D000068181:Prunus dulcis; D012475:Salmonella; D013696:Temperature
keywords: Escherichia coli O157:H7; Food safety; High-intensity light; Light-emitting diodes; Salmonella; Surrogate