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Ryu V, Uknalis J, Ngo H, Jin T, Fan X. Coating with phenolic branched-chain fatty acid reduces Listeria innocua populations on apple fruit. Int J Food Microbiol 2024; 419:110748. [PMID: 38772217 DOI: 10.1016/j.ijfoodmicro.2024.110748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/25/2024] [Accepted: 05/13/2024] [Indexed: 05/23/2024]
Abstract
An antimicrobial coating was produced by mixing phenolic branched-chain fatty acid (PBC-FA) with glycerol and a carboxymethyl cellulose solution (CMC) at pH 7. The resulting PBC-FA-CMC solution formed an emulsion with an average droplet size of 77 nm. The emulsion in the coating solution was stable for at least 30 days at 20 °C. The in vitro antimicrobial activity of the film formed from the PBC-FA emulsion was tested against a mixture of 3 strains of Listeria innocua (7 log CFU/mL). Film with a concentration of 1000 μg/mL of PBC-FA effectively reduced the population of L. innocua below the limit of detection (<1.48 log CFU/mL) in vitro. The effect of the 1000 μg/mL PBC-FA-CMC coating formulation was then evaluated against L. innocua inoculated on "Gala" apples. Results showed that compared with the non-coated control, the coating reduced L. innocua populations by ~2 log CFU/fruit and ~6 log CFU/fruit on the apple when enumerated on tryptic soy agar and selective media (PALCAM), respectively, indicating that PBC-FA applied as a coating on apples resulted in the sub-lethal injury of bacterial cells. When L. innocua was inoculated onto PBC-FA-coated apples, the L. innocua population decreased by ~4 log CFU/fruit during 14 days of shelf-life at 20 °C. The PBC-FA coating lowered the moisture loss but did not affect the color, firmness, or soluble solids content of apples during the 14-day at 20 °C. Overall, this study revealed that there is a potential that PBC-FA can be used as an antimicrobial coating to inactivate Listeria and preserve the quality of apples.
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Affiliation(s)
- Victor Ryu
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA.
| | - Joseph Uknalis
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA.
| | - Helen Ngo
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA.
| | - Tony Jin
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA.
| | - Xuetong Fan
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA.
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Ryu V, Chuesiang P, Uknalis J, Ngo H, Jin T, Fan X. Bio-based phenolic branched-chain fatty acid in wash water reduced populations of Listeria innocua on apple fruit. Heliyon 2024; 10:e24901. [PMID: 38314263 PMCID: PMC10837536 DOI: 10.1016/j.heliyon.2024.e24901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 01/11/2024] [Accepted: 01/16/2024] [Indexed: 02/06/2024] Open
Abstract
Phenolic branched-chain fatty acid (PBC-FA) emulsion was produced by dissolving it in ethanol and mixing with water (pH 7). The resulting monodispersed emulsion droplets were approximately 200 nm in diameter. The stability of the emulsion was evaluated by storing it at 4 and 20 °C for 30 days. The antimicrobial activity of the PBC-FA emulsion was tested against Escherichia coli and Listeria innocua (8 log CFU/mL) by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using a microdilution method. The PBC-FA was effective against L. innocua with MIC and MBC of 14.1 μg/mL and caused membrane permeation as determined with SEM and Live/Dead cell assay, but was not effective against E. coli O157:H7 at the tested concentrations (5-250 μg/mL). We also evaluated PBC-FA emulsion's potential to be used as a wash against L. innocua inoculated on apples. The results showed that the 500 μg/mL PBC-FA emulsion with 5 % ethanol had equivalent antimicrobial activity (2-3 logs reductions) against L. innocua as the 20 μg/mL chlorine solution, a commonly used sanitizer. 500 μg/mL PBC-FA emulsion had better antimicrobial efficacy when organic matter (chemical oxygen demand: 9.0 g/L) was present compared to 20 μg/mL of chlorine. The effect of PBC-FA on the quality of the apples, was determined by measuring changes in color, firmness, and soluble solids content over a 14-day storage period at 20 °C. The quality of the apples was not affected by PBC-FA over the 14-day storage period, suggesting that PBC-FA emulsion can be used as a wash for apples without affecting their quality.
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Affiliation(s)
- Victor Ryu
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA, 19038, USA
| | - Piyanan Chuesiang
- Department of Food Technology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Joseph Uknalis
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA, 19038, USA
| | - Helen Ngo
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA, 19038, USA
| | - Tony Jin
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA, 19038, USA
| | - Xuetong Fan
- USDA, ARS, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA, 19038, USA
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Ryu V, Uknalis J, Corradini MG, Chuesiang P, McLandsborough L, Ngo H, Jin T, Fan X. Mechanism of Synergistic Photoinactivation Utilizing Curcumin and Lauric Arginate Ethyl Ester against Escherichia coli and Listeria innocua. Foods 2023; 12:4195. [PMID: 38231609 DOI: 10.3390/foods12234195] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 11/16/2023] [Accepted: 11/18/2023] [Indexed: 01/19/2024] Open
Abstract
This study investigated the mechanism of how lauric arginate ethyl ester (LAE) improves the photoinactivation of bacteria by curcumin after diluting the 100 µmol/L stock curcumin-LAE micelle solution to the concentration used during the treatment based on the curcumin concentration. The photoinactivation of bacteria was conducted by irradiating the 1 µmol/L curcumin-LAE solution containing cocktails of Escherichia coli and Listeria innocua strains (7 log CFU/mL) for 5 min with UV-A light (λ = 365 nm). The changes in solution turbidity, curcumin stability, and bacterial morphology, viability, and recovery were observed using SEM, TEM, and live/dead cell assays. The study found that LAE enhances the photoinactivation of bacteria by increasing the permeability of cell membranes which could promote the interaction of reactive oxygen species produced by photosensitized curcumin with the cell components. The combination of curcumin and LAE was demonstrated to be more effective in inhibiting bacterial recovery at pH 3.5 for E. coli, while LAE alone was more effective at pH 7.0 for L. innocua.
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Affiliation(s)
- Victor Ryu
- United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA
| | - Joseph Uknalis
- United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA
| | - Maria G Corradini
- Food Science Department & Arrell Food Institute, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Piyanan Chuesiang
- Department of Food Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Lynne McLandsborough
- Department of Food Science, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Helen Ngo
- United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA
| | - Tony Jin
- United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA
| | - Xuetong Fan
- United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA
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