Food Protection Trends - September/October 2023 - 377
it to survive sanitation treatments, demonstrating concern
for the safety of food products (27). Researchers have
been focusing efforts on understanding this pathogenic
microorganism's ability to infect, survive, and persist in
food processing environments and on equipment; however,
the rising numbers of L. monocytogenes outbreaks linked to
fresh produce have hastened the need to understand how to
effectively control this pathogen on produce.
The prevalence, persistence, and diversity through which
L. monocytogenes infects fresh produce is a growing concern,
especially considering the zero-tolerance regulation put in
place by the U.S. Food and Drug Administration for RTE
products (2). Equipment such as picking bags and storage
bins used during the harvesting and handling of produce are
known reservoirs of microbial biofilms (18, 25, 30). Their
regular food-contact surfaces provide a niche environment
for biofilms to persist even after sanitizer application.
The use of chemical sanitizers is a common practice
within the produce industry for controlling Listeria spp.
Most studies have analyzed the effect of commercially
available sanitizers such as peroxyacetic acid (PAA), ozone,
halogen-based compounds, hydrogen peroxide, acid anionic
compounds, and quaternary ammonium compounds on
food processing surfaces (3, 12, 16). The implementation
of technologies using UV-C light has provided a method
for disinfecting surfaces that may eliminate the need for
mechanical scrubbing (1). Today, food safety is moving
toward synergistic processes of simultaneous or sequential
germicidal applications to obtain greater pathogen reduction
(7). Studies analyzing the combined effects of UV light
and chemical treatment have found that such combined
applications have higher antimicrobial effects than singleapplication
treatments. Ding et al. (11) found that when
treating leafy greens, the simultaneous application of UV-A
light and benzoic acid was most effective. The combined
use of chemical and physical means of sanitation has been
presented as a positive strategy to overcome contamination in
food processing environments. Based on a survey conducted
among stakeholders in the tree fruit production industry
(in the Midwest), three favored materials for storing and
harvesting produce were identified: nylon (for picking bags),
wood, and plastic (for bins).
The objective of this study was to investigate the survival of
L. monocytogenes biofilms on wood, nylon, and polycarbonate
produce-harvesting materials after treatment with chemical
sanitizers alone and/or concurrent with UV-C light. The
chemical sanitizers lactic acid, SDC and thymol were
selected to represent nontoxic or generally recognized as safe
chemicals. All of these products are commercially available
and certified organic (GRAS). Their market price places
them in a slightly higher category than bleach; nevertheless,
these products are accessible and commonly used in the
organic farming sector.
MATERIALS AND METHODS
Bacterial strains
Three strains of L. monocytogenes were used in this study to
form biofilms: L2624 (serotype 1/2b) and L2626 (serotype
1/2a), isolated from the 2001 U.S. cantaloupe outbreak,
and J2230 (serotype 4b) from a clinical sample (21). All
strains were kept on CyroCare Bacteria Preserver beads
(Key Scientific, Stamford, TX, USA) and stored at −80°C
until used in experiments. An L. monocytogenes cocktail, as
described by Mendez et al. (21), was created by combining
individual strains in equal ratio to reach an initial population
of ca. 1 × 108
CFU/ml.
Substrate materials
The materials selected for this study included wood,
nylon, and polycarbonate, all of which are representative
of substrates used during the harvesting and handling of
tree fruit production. Coupons made of polycarbonate
(1.27 cm in diameter) were purchased from BioSurface
Technologies (Bozeman, MT, USA). Wood coupons were
made of plywood of unfinished basswood (Tilia americana)
purchased from a local store and cut into coupons of 1.27
cm in diameter. Nylon fabric was obtained from a local
store and was cut into 2- by 2-cm squares to fit within the
rods of the reactor.
Biofilm formation
Based on a protocol developed in our laboratory (21),
with slight modifications, biofilms were grown in a Centers
for Disease Control and Prevention (CDC) biofilm reactor
(BioSurface Technologies) for up to 96 h. To begin the 24-h
batch phase, 1 ml of L. monocytogenes cocktail was used to
inoculate the reactor. This phase was followed by an additional
72 h of continuous nutrient flow at a rate of 8 ml/min by using
tryptic soy broth (Difco, BD, Sparks, MD, USA). The reactor
was maintained at 20 ± 2°C for 96 h of incubation.
Chemical sanitizer and UV-C light
The following chemical sanitizers were used to evaluate
efficacy against L. monocytogenes biofilms: 4% lactic acid
solution (Purac, Corbion, Blair, NE, USA), confirmed using
a lactic acid test kit (ChemWorld, Kennesaw, GA, USA);
5% SDC-based sanitizer, as per label (PURE Bioscience,
Inc., El Cajon, CA, USA); and 0.23% thymol solution, as
per label (Bioesque Solutions, Lighthouse Point, FL, USA).
Because microbial DNA absorbs UV-C light between 200
and 300 nm, with optimal absorption at ca. 260 nm, the
lamp (Lumalier, Memphis, TN, USA) used as the emission
source of the UV-C light was set at 254 nm for germicidal and
disinfection applications. The power output was monitored
using a radiometer (Sper Scientific Ltd., Scottsdale, AZ,
USA) during all of the experiments to ensure constant UV-C
light irradiance.
September/October Food Protection Trends 377
Food Protection Trends - September/October 2023
Table of Contents for the Digital Edition of Food Protection Trends - September/October 2023
Salmonella Prevalence is Low in Deep Tissue Lymph Nodes of Hog Carcasses from a Pork Processing Plant in Alberta, Canada
Combined Effects of Sanitizers and UV-C Light on Listeria monocytogenes Biofilm Growth and Survivability on Produce-Harvesting Materials Used in the Tree Fruit Production Industry
Identifying Predictors of Safe Food Handling Practices among Canadian Households with Children Under Eighteen Years
Cleaning and Sanitizing in Produce Facilities: Identifying Compliance Gaps and Associated Training Needs, Opportunities and Preferences
Beyond the Bio Tori Stivers
PDG Highlight Low-Water Activity Foods PDG
General Interest Strengthening the Mauritius Food Control System for Enhanced Public Health and Life Protection
Industry Products
Coming Events
Food Protection Trends - September/October 2023 - Cover1
Food Protection Trends - September/October 2023 - Cover2
Food Protection Trends - September/October 2023 - 369
Food Protection Trends - September/October 2023 - 370
Food Protection Trends - September/October 2023 - 371
Food Protection Trends - September/October 2023 - 372
Food Protection Trends - September/October 2023 - 373
Food Protection Trends - September/October 2023 - 374
Food Protection Trends - September/October 2023 - 375
Food Protection Trends - September/October 2023 - Combined Effects of Sanitizers and UV-C Light on Listeria monocytogenes Biofilm Growth and Survivability on Produce-Harvesting Materials Used in the Tree Fruit Production Industry
Food Protection Trends - September/October 2023 - 377
Food Protection Trends - September/October 2023 - 378
Food Protection Trends - September/October 2023 - 379
Food Protection Trends - September/October 2023 - 380
Food Protection Trends - September/October 2023 - 381
Food Protection Trends - September/October 2023 - 382
Food Protection Trends - September/October 2023 - Salmonella Prevalence is Low in Deep Tissue Lymph Nodes of Hog Carcasses from a Pork Processing Plant in Alberta, Canada
Food Protection Trends - September/October 2023 - 384
Food Protection Trends - September/October 2023 - 385
Food Protection Trends - September/October 2023 - 386
Food Protection Trends - September/October 2023 - 387
Food Protection Trends - September/October 2023 - 388
Food Protection Trends - September/October 2023 - 389
Food Protection Trends - September/October 2023 - 390
Food Protection Trends - September/October 2023 - Identifying Predictors of Safe Food Handling Practices among Canadian Households with Children Under Eighteen Years
Food Protection Trends - September/October 2023 - 392
Food Protection Trends - September/October 2023 - 393
Food Protection Trends - September/October 2023 - 394
Food Protection Trends - September/October 2023 - 395
Food Protection Trends - September/October 2023 - 396
Food Protection Trends - September/October 2023 - 397
Food Protection Trends - September/October 2023 - 398
Food Protection Trends - September/October 2023 - 399
Food Protection Trends - September/October 2023 - 400
Food Protection Trends - September/October 2023 - 401
Food Protection Trends - September/October 2023 - 402
Food Protection Trends - September/October 2023 - 403
Food Protection Trends - September/October 2023 - 404
Food Protection Trends - September/October 2023 - 405
Food Protection Trends - September/October 2023 - 406
Food Protection Trends - September/October 2023 - 407
Food Protection Trends - September/October 2023 - 408
Food Protection Trends - September/October 2023 - Cleaning and Sanitizing in Produce Facilities: Identifying Compliance Gaps and Associated Training Needs, Opportunities and Preferences
Food Protection Trends - September/October 2023 - 410
Food Protection Trends - September/October 2023 - 411
Food Protection Trends - September/October 2023 - 412
Food Protection Trends - September/October 2023 - 413
Food Protection Trends - September/October 2023 - 414
Food Protection Trends - September/October 2023 - 415
Food Protection Trends - September/October 2023 - 416
Food Protection Trends - September/October 2023 - 417
Food Protection Trends - September/October 2023 - 418
Food Protection Trends - September/October 2023 - 419
Food Protection Trends - September/October 2023 - Beyond the Bio Tori Stivers
Food Protection Trends - September/October 2023 - 421
Food Protection Trends - September/October 2023 - 422
Food Protection Trends - September/October 2023 - PDG Highlight Low-Water Activity Foods PDG
Food Protection Trends - September/October 2023 - 424
Food Protection Trends - September/October 2023 - 425
Food Protection Trends - September/October 2023 - General Interest Strengthening the Mauritius Food Control System for Enhanced Public Health and Life Protection
Food Protection Trends - September/October 2023 - 427
Food Protection Trends - September/October 2023 - 428
Food Protection Trends - September/October 2023 - 429
Food Protection Trends - September/October 2023 - 430
Food Protection Trends - September/October 2023 - 431
Food Protection Trends - September/October 2023 - Industry Products
Food Protection Trends - September/October 2023 - 433
Food Protection Trends - September/October 2023 - 434
Food Protection Trends - September/October 2023 - 435
Food Protection Trends - September/October 2023 - 436
Food Protection Trends - September/October 2023 - 437
Food Protection Trends - September/October 2023 - 438
Food Protection Trends - September/October 2023 - 439
Food Protection Trends - September/October 2023 - Coming Events
Food Protection Trends - September/October 2023 - Cover3
Food Protection Trends - September/October 2023 - Cover4
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