Development of miniaturized, cost- and time-effective high-throughput screening of antimicrobial treatments against foodborne pathogens on meat matrices

Foodborne outbreaks continue to occur in the US, which has negative economic and health impacts on the population. Therefore, the food industry strives to ensure food products have the highest standards of quality and safety. A widely used strategy to ensure safety of food products is the use of antimicrobials. Antimicrobials are physical or chemical interventions that inhibit pathogenic bacteria in food products, some of these compounds have been widely studied and have been granted the Generally Recognized as Safe (GRAS) status by the Food and Drug Administration (FDA). However, it has been shown before that antimicrobials’ activity is highly influenced by the matrix and the target microorganism. Furthermore, hundreds of substances and/or physical processes have been proposed before to be used as antimicrobial treatments in a wide variety of foods (meat, dairy, vegetables, fruits, etc.) against common foodborne pathogens (Salmonella enterica, Listeria monocytogenes, Escherichia coli O157:H7, etc.). Therefore, the development of efficient tools to screen antimicrobials on specific food matrices is highly relevant. This work reflects a proposal for the development of screening tools against Listeria monocytogenes and Salmonella on Ready-to-Eat (RTE) meat products and raw pork meat, respectively. RTE meat products such as deli ham have been linked to foodborne outbreaks, where Listeria monocytogenes has been identified as the disease-causing agent. The objective of Chapter 2 was to validate a miniature ham model (MHM) against the ham slice method and to screen antimicrobial combinations to control LM on ham using response surface methodology (RSM) as a time- and cost-effective high-throughput screening tool. The effect of nisin (Ni), potassium lactate sodium acetate (PLSDA), lauric arginate (LAG), lytic bacteriophage (P100), and Ɛ-polylysine (EPL) added alone, or in combination, was determined on the MHM over 12 days of storage. Results showed the MHM accurately mimics the ham slice method since no statistical differences were found (p>0.05) on LM cell counts after 12 days of storage at 4°C when hams were untreated or treated with 50 ppm Ni. All tested antimicrobials were effective on reducing LM cell counts on ham when added alone. A significant antagonistic interaction (p<0.01) was identified by the Response Surface Methodology (RSM) model between LAG and P100, since this antimicrobial combination caused the LM cell counts to increase 2.2 log CFU/g after 12 days of storage. Two interactions, between Ni and EPL (p<0.1), and Ni and P100 (p<0.1), showed possible synergistic effects against LM on the MHM. Other interactions were clearly non-significant (p>0.1), suggesting additive effects. Then, Chapter 3 focused on the use of plant essential oils as potential clean-label strategies to control Listeria monocytogenes on deli ham. This study implemented a high-throughput, bioluminescence screening tool to identify antimicrobial treatments to control the growth of L. monocytogenes on deli-ham. Bioluminescent L. monocytogenes Xen19 was inoculated on the surface of the hams at ~5 log (CFU/g). A library of 30 essential oils was tested directly on the surface of the ham at 0.05%. On day 12, light emission (Relative Light Units [RLUs] at 400-750 nm) was read directly from the surface of the ham disks as an indirect measurement of L. monocytogenes growth. Oils that limited L. monocytogenes growth as measured by less light emission than non-treated hams were considered promising antimicrobial compounds. Only cassia, dillweed, garlic, and peru oil each significantly reduced light emission of L. monocytogenes Xen 19 compared to no-treatment controls (controls increased 1.8±0.3 log RLU after 12 days at 4ºC). The remaining 26 oils had RLU levels indistinguishable from the no-treatment control and, therefore, were considered non-effective antimicrobial compounds. Finally, Chapter 4 implemented the previously mentioned RSM model into raw pork to inhibit Salmonella Typhimurium. To efficiently screen possible treatments, 30 essential oils (EOs), 3 organic acids (lactic, formic, and peracetic acid), and 2 food preservatives (potassium sorbate and sodium propionate) at commercial working concentrations were individually added to miniaturized (69 cm3) disks of pork loin ends destined for comminuted products against Salmonella Typhimurium ATCC 19585. Lactic acid (LA) 1.25%, formic acid (FA) 0.25%, cumin (CMN) 0.25%, clove (CLV) 0.25%, peppermint (PPP) 0.5%, and spearmint (SPT) 0.5% were added as independent variables to build a RSM model based on a Doehlert matrix (DM-RSM). The DM-RSM model was significant (P<0.0001), no lack-of-fit was detected (P=0.248), and the residual standard error (RSD) was 0.15 log CFU/g. The fitted model identified LA, FA, CMN, PPP, and SPT as significant when added alone to the pork loin disks. However, no significant interactions between antimicrobials were found in the model. A laboratory-scale validation of the model was carried out on pork loin end slices (48.03.0 g, approximately) inoculated with Salmonella Typhimurium ATCC 19585. Single and paired antimicrobial treatments were sprayed on the surface of the slices before bacterial enumeration. The validation results showed that paired combinations of LA with the other 5 treatments were not significantly different from the untreated control group (P>0.05). FA in combination with other treatments significantly reduced bacterial cell counts compared to control (P<0.05), except for the combination of FA and LA (P=0.303). No paired EO combination was significantly different from the untreated control (P>0.05). While this screening did not identify novel synergistic combinations, our approach to screen a variety of chemical compounds by implementing a miniaturized pork loin disk model, allowed us to reduce the number of potential antimicrobial compounds from 35 to 11, making it an efficient screening tool.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Food Science & Human Nutrition

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Resendiz Moctezuma, Cristina

Contributors dc:contributor

• Miller, Michael J
• Stasiewicz, Matthew J
• Harsh, Bailey N
• Feng, Hao

• Antimicrobial
• Pathogen
• Screening
• Listeria Monocytogenes
• Salmonella

Statement dc:rights

• Copyright 2023 Cristina Resendiz Moctezuma

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/122194

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F122194