Inhibitory effect of caprylic acid and mild heat on Cronobacter spp. (Enterobacter sakazakii) in reconstituted infant formula and determination of injury by flow cytometry

Hye In Jang, Min-Suk Rhee

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

The combined effects of caprylic acid and mild heat were investigated to ascertain their impact on Cronobacter spp. (E. sakazakii) in reconstituted infant formula. Samples containing a mixture of 3 strains of Cronobacter spp. (10 7 to 10 8 CFU/ml) were prepared with various concentrations of caprylic acid (5, 10, 20, and 30 mM) and were then heated to 45, 50, and 55 °C. The inhibitory effect of the combined treatment resulted in a synergistic effect, in which Cronobacter spp. numbers were reduced much more rapidly with increased temperatures and concentrations of caprylic acid. When samples were treated with 30 mM caprylic acid, the time required to reduce Cronobacter spp. cell numbers to an approximate reduction of 7.8 log CFU/ml was 60 min at 45 °C, 20 min at 50 °C, and 10 min at 55 °C. In the validation assay using a low population of Cronobacter spp. (approximately 10 3 log CFU/ml), no recovery of injured cells was observed after samples were treated with 10 mM caprylic acid for 20 min at 55 °C, 20 mM caprylic acid for 10 min at 50 °C and 55 °C, and 30 mM caprylic acid for 10 min at 45 °C to 55 °C. To determine the bactericidal mechanism of caprylic acid, membrane integrity was examined by fluorescent staining followed by flow cytometry and confocal microscopy. Increased cellular inactivation was associated with increased propidium iodide staining, indicating damage to the cell membrane of Cronobacter spp.. Overall, these data indicate that the addition of this natural antimicrobial agent to infant formula may have potential use for controlling microbes prior to consumption at lower heating temperatures. The study also provides a complementary understanding of the mode of action of caprylic acid on Cronobacter spp.

Original languageEnglish
Pages (from-to)113-120
Number of pages8
JournalInternational Journal of Food Microbiology
Volume133
Issue number1-2
DOIs
Publication statusPublished - 2009 Jul 31

Fingerprint

Cronobacter
Cronobacter sakazakii
octanoic acid
Infant Formula
Flow cytometry
infant formulas
flow cytometry
Flow Cytometry
Hot Temperature
heat
Acids
Wounds and Injuries
Staining and Labeling
Antimicrobial agents
Temperature
Propidium
Confocal microscopy
Cell membranes
Anti-Infective Agents
Confocal Microscopy

Keywords

  • Caprylic acid
  • Confocal laser scanning microscopy
  • Cronobacter spp.
  • Flow cytometry
  • Infant formula
  • Mild heat

ASJC Scopus subject areas

  • Food Science
  • Microbiology
  • Safety, Risk, Reliability and Quality

Cite this

@article{0e43928d8b454e04a638bc01e43d6853,
title = "Inhibitory effect of caprylic acid and mild heat on Cronobacter spp. (Enterobacter sakazakii) in reconstituted infant formula and determination of injury by flow cytometry",
abstract = "The combined effects of caprylic acid and mild heat were investigated to ascertain their impact on Cronobacter spp. (E. sakazakii) in reconstituted infant formula. Samples containing a mixture of 3 strains of Cronobacter spp. (10 7 to 10 8 CFU/ml) were prepared with various concentrations of caprylic acid (5, 10, 20, and 30 mM) and were then heated to 45, 50, and 55 °C. The inhibitory effect of the combined treatment resulted in a synergistic effect, in which Cronobacter spp. numbers were reduced much more rapidly with increased temperatures and concentrations of caprylic acid. When samples were treated with 30 mM caprylic acid, the time required to reduce Cronobacter spp. cell numbers to an approximate reduction of 7.8 log CFU/ml was 60 min at 45 °C, 20 min at 50 °C, and 10 min at 55 °C. In the validation assay using a low population of Cronobacter spp. (approximately 10 3 log CFU/ml), no recovery of injured cells was observed after samples were treated with 10 mM caprylic acid for 20 min at 55 °C, 20 mM caprylic acid for 10 min at 50 °C and 55 °C, and 30 mM caprylic acid for 10 min at 45 °C to 55 °C. To determine the bactericidal mechanism of caprylic acid, membrane integrity was examined by fluorescent staining followed by flow cytometry and confocal microscopy. Increased cellular inactivation was associated with increased propidium iodide staining, indicating damage to the cell membrane of Cronobacter spp.. Overall, these data indicate that the addition of this natural antimicrobial agent to infant formula may have potential use for controlling microbes prior to consumption at lower heating temperatures. The study also provides a complementary understanding of the mode of action of caprylic acid on Cronobacter spp.",
keywords = "Caprylic acid, Confocal laser scanning microscopy, Cronobacter spp., Flow cytometry, Infant formula, Mild heat",
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T1 - Inhibitory effect of caprylic acid and mild heat on Cronobacter spp. (Enterobacter sakazakii) in reconstituted infant formula and determination of injury by flow cytometry

AU - Jang, Hye In

AU - Rhee, Min-Suk

PY - 2009/7/31

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N2 - The combined effects of caprylic acid and mild heat were investigated to ascertain their impact on Cronobacter spp. (E. sakazakii) in reconstituted infant formula. Samples containing a mixture of 3 strains of Cronobacter spp. (10 7 to 10 8 CFU/ml) were prepared with various concentrations of caprylic acid (5, 10, 20, and 30 mM) and were then heated to 45, 50, and 55 °C. The inhibitory effect of the combined treatment resulted in a synergistic effect, in which Cronobacter spp. numbers were reduced much more rapidly with increased temperatures and concentrations of caprylic acid. When samples were treated with 30 mM caprylic acid, the time required to reduce Cronobacter spp. cell numbers to an approximate reduction of 7.8 log CFU/ml was 60 min at 45 °C, 20 min at 50 °C, and 10 min at 55 °C. In the validation assay using a low population of Cronobacter spp. (approximately 10 3 log CFU/ml), no recovery of injured cells was observed after samples were treated with 10 mM caprylic acid for 20 min at 55 °C, 20 mM caprylic acid for 10 min at 50 °C and 55 °C, and 30 mM caprylic acid for 10 min at 45 °C to 55 °C. To determine the bactericidal mechanism of caprylic acid, membrane integrity was examined by fluorescent staining followed by flow cytometry and confocal microscopy. Increased cellular inactivation was associated with increased propidium iodide staining, indicating damage to the cell membrane of Cronobacter spp.. Overall, these data indicate that the addition of this natural antimicrobial agent to infant formula may have potential use for controlling microbes prior to consumption at lower heating temperatures. The study also provides a complementary understanding of the mode of action of caprylic acid on Cronobacter spp.

AB - The combined effects of caprylic acid and mild heat were investigated to ascertain their impact on Cronobacter spp. (E. sakazakii) in reconstituted infant formula. Samples containing a mixture of 3 strains of Cronobacter spp. (10 7 to 10 8 CFU/ml) were prepared with various concentrations of caprylic acid (5, 10, 20, and 30 mM) and were then heated to 45, 50, and 55 °C. The inhibitory effect of the combined treatment resulted in a synergistic effect, in which Cronobacter spp. numbers were reduced much more rapidly with increased temperatures and concentrations of caprylic acid. When samples were treated with 30 mM caprylic acid, the time required to reduce Cronobacter spp. cell numbers to an approximate reduction of 7.8 log CFU/ml was 60 min at 45 °C, 20 min at 50 °C, and 10 min at 55 °C. In the validation assay using a low population of Cronobacter spp. (approximately 10 3 log CFU/ml), no recovery of injured cells was observed after samples were treated with 10 mM caprylic acid for 20 min at 55 °C, 20 mM caprylic acid for 10 min at 50 °C and 55 °C, and 30 mM caprylic acid for 10 min at 45 °C to 55 °C. To determine the bactericidal mechanism of caprylic acid, membrane integrity was examined by fluorescent staining followed by flow cytometry and confocal microscopy. Increased cellular inactivation was associated with increased propidium iodide staining, indicating damage to the cell membrane of Cronobacter spp.. Overall, these data indicate that the addition of this natural antimicrobial agent to infant formula may have potential use for controlling microbes prior to consumption at lower heating temperatures. The study also provides a complementary understanding of the mode of action of caprylic acid on Cronobacter spp.

KW - Caprylic acid

KW - Confocal laser scanning microscopy

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KW - Flow cytometry

KW - Infant formula

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