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Communication

Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder

1
Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Court, Columbus, OH 43210, USA
2
Botany and Microbiology Department, Faculty of Science, Benha University, Benha 13518, Egypt
3
Department of Microbiology, The Ohio State University, 105 Biological Sciences Building, 484 West 12th Avenue, Columbus, OH 43210, USA
*
Author to whom correspondence should be addressed.
Academic Editor: María-Jesús Grilló
Microorganisms 2021, 9(2), 421; https://doi.org/10.3390/microorganisms9020421
Received: 17 January 2021 / Revised: 4 February 2021 / Accepted: 14 February 2021 / Published: 18 February 2021
(This article belongs to the Special Issue Salmonella and Salmonellosis)
Some Salmonella enterica strains survive well in low-water activity (low-aw) foods and cause frequent salmonellosis outbreaks in these products. Methods are needed to overcome such desiccation-resistant Salmonella and to improve the safety of low-aw foods. Building on a recent finding, we hypothesized that natural antimicrobial food additives, which are active against cytoplasmic membrane, could overcome this desiccation resistance phenomenon, and thus, sensitize the pathogen to drying and mild processing. Food additives were screened for the ability to cause leakage of intracellular potassium ions; retention of these ions is vital for protecting Salmonella against desiccation. Two antimicrobial food additives, carvacrol and thymol, caused considerable potassium leakage from the desiccation-resistant S. enterica serovars, Tennessee and Livingstone. Thus, carvacrol and thymol were investigated for their ability to sensitize the desiccation-adapted S. enterica to heat treatment. The combined use of food additives, at their minimum inhibitory concentrations, with heat treatment at 55 °C for 15 min caused 3.1 ± 0.21 to more than 5.5 log colony forming unit (CFU)/mL reduction in desiccation-adapted S. enterica, compared to 2.4 ± 0.53–3.2 ± 0.11 log CFU/mL reduction by sole heat treatment. Carvacrol was the additive that caused the greatest potassium leakage and sensitization of Salmonella to heat; hence, the application of this compound was investigated in a food model against Salmonella Typhimurium ASD200. Addition of carvacrol at 200 or 500 ppm into liquid milk followed by spray-drying reduced the strain’s population by 0.9 ± 0.02 and 1.3 ± 0.1 log CFU/g, respectively, compared to 0.6 ± 0.02 log CFU/g reduction for non-treated spray-dried milk. Additionally, freeze-drying of milk treated with high levels of carvacrol (5000 ppm) reduced the population of Salmonella Typhimurium ASD200 by more than 4.5 log CFU/g, compared to 1.1 ± 0.4 log CFU/g reduction for the freeze-dried untreated milk. These findings suggest that carvacrol can combat desiccation-resistant S. enterica, and thus, potentially improve the safety of low-aw foods. View Full-Text
Keywords: natural antimicrobials; food additives; Salmonella enterica; desiccation resistance; low-aw foods natural antimicrobials; food additives; Salmonella enterica; desiccation resistance; low-aw foods
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MDPI and ACS Style

Abdelhamid, A.G.; Yousef, A.E. Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder. Microorganisms 2021, 9, 421. https://doi.org/10.3390/microorganisms9020421

AMA Style

Abdelhamid AG, Yousef AE. Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder. Microorganisms. 2021; 9(2):421. https://doi.org/10.3390/microorganisms9020421

Chicago/Turabian Style

Abdelhamid, Ahmed G., and Ahmed E. Yousef 2021. "Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder" Microorganisms 9, no. 2: 421. https://doi.org/10.3390/microorganisms9020421

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