Plant-based antimicrobials inactivate Listeria monocytogenes and Salmonella enterica on melons grown in different regions of the United States

Authors: ZHU, LIBIN - University Of Arizona; WEI, QI - University Of Arizona; PORCHAS, MARTIN - University Of Arizona; BRIERLEY, PAUL - University Of Arizona; Friedman, Mendel; CROSBY, KEVIN - Texas A&M University; PATIL, BHIMANAGOUDA - Texas A&M University; RAVISHANKAR, SADHANA - University Of Arizona

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2021
Publication Date: 7/29/2021
Citation: Zhu, L., Wei, Q., Porchas, M., Brierley, P., Friedman, M., Crosby, K., Patil, B., Ravishankar, S. 2021. Plant-based antimicrobials inactivate Listeria monocytogenes and Salmonella enterica on melons grown in different regions of the United States. Food Microbiology. 101. Article 103876. https://doi.org/10.1016/j.fm.2021.103876.
DOI: https://doi.org/10.1016/j.fm.2021.103876

Interpretive Summary: Because melons have been involved in several foodborne outbreaks, effective control measures are needed for improving melon safety. One of the deadliest outbreaks of foodborne illness in the United States was the 2011 outbreak of listeriosis due to the consumption of contaminated cantaloupes that caused 147 illnesses and 33 deaths in 28 states. The objective of this study was to evaluate the efficacy of plant-based antimicrobials olive extract and oregano oil against the foodborne pathogens Salmonella Newport and Listeria monocytogenes on melon rinds. The plant-based antimicrobials olive extract and oregano oil reduced Salmonella Newport and Lisetria monocytogenes populations on all the melon rind samples for various melon types, varieties, or growing locations that included Georgia, Arizona, Texas, North Carolina, Indiana and California. In general, oregano oil had better antimicrobial activity than the olive extract. The antimicrobial treatments were more effective on Salmonella than on Listeria and exhibited better reductions on honeydews than on cantaloupes. Overall, the antimicrobial treatments showed better effectiveness on melons grown in North Carolina and Indiana than in other regions. This study demonstrated the potential of these plant-based antimicrobials to reduce Salmonella and Listeria contamination on melons grown in several regions of the United States. Further sensory and texture analysis should be done to evaluate the consumer acceptance of the antimicrobial treated melons. This study was supported by the USDA-NIFA-SCRI-2017-51181-26834 grant through the National Center of Excellence for Melons at the Vegetable and Fruit Improvement Center of the Texas A&M University.

Technical Abstract: Because melons have been involved in several foodborne outbreaks, effective control measures are needed for improving melon safety. The objective of this study was to evaluate the efficacy of plant-based antimicrobials against the foodborne pathogens Salmonella Newport and Listeria monocytogenes on melon rinds. Melon varieties were grown in Georgia, Arizona, Texas, North Carolina, Indiana and California, and shipped to Tucson, AZ. The tested melons included 4 cantaloupe varieties, and 3 honeydew varieties. Melon rinds were cut into 10 g pieces and inoculated with 6 log colony forming units (CFU)/mL of the pathogenic bacteria. Rind samples were then immersed in 5% olive extract or 0.5% oregano oil antimicrobial solution and gently agitated for 2 min. Phosphate buffered saline was used as a control. After treatment, the samples were stored at 4°C and the surviving populations of S. Newport and L. monocytogenes were enumerated at Day 0 and 3. The rind samples were mixed with 90 mL of buffered peptone water and stomached for 2 min. Serial dilutions were plated on xylose lysine desoxycholate agar and Modified Oxford agar for enumeration of S. Newport and L. monocytogenes, respectively. The plant-based antimicrobials reduced the population of both pathogens on all rind samples, regardless of the melon types, varieties or growing locations. Compared to the phosphate buffer control, the plant-based antimicrobial treatments caused 1.7-3.6 and 1.3-4.0 log reductions in populations of Salmonella and Listeria, respectively. In most cases, the antimicrobial treatments reduced pathogen populations to below the detection limit (1 CFU/g) at Day 3. In general, oregano oil had better antimicrobial activity than the olive extract. The antimicrobial treatments were more effective on Salmonella than on Listeria and exhibited better reductions on honeydews than on cantaloupes. The results showed that plant-based antimicrobials have the potential to be used as sanitizers for decontaminating melons.