Inactivation of Escherichia coli with power ultrasound in apple cider

Edgar Ugarte-Romero, Hao Feng, Scott E. Martin, Keith R. Cadwallader, Scott J. Robinson

Research output: Contribution to journalArticlepeer-review


The use of acoustic energy to secure apple cider safety was explored. Inactivation tests were performed with Escherichia coli K12 at 40°C, 45°C, 50°C, 55°C, and 60°C with and without ultrasound, followed by a validation test with E. coli O157:H7 at 60°C. The cell morphology was observed with environmental scanning electron microscopy for samples treated at 40°C and 60°C. Physical quality attributes of the apple cider (pH, titratable acidity, °Brix, turbidity, and color) were compared for treated samples. The inactivation tests showed that sonication increased E. coli K12 cell destruction by 5.3-log, 5.0-log, and 0.1-log cycles at 40°C, 50°C, and 60°C, respectively. The additional destruction due to sonication was more pronounced at sublethal temperatures. At the lethal temperature of 60°C, the rate of death by ultrasound was not significantly different compared with the thermal-alone treatment. The inactivation of E. coli K12 with heat was described by 1st-order kinetics, especially at 50°C and 60°C. For ultrasound treatments, concave upward survival curves were observed, which had a shape factor in the range of 0.547 to 0.720 for a Weibull distribution model. Extensive damage for ultrasound treated E. coli K12 cells, including cell perforation, was observed. Perforation is a unique phenomenon found on ultrasound-treated cells that could be caused by liquid jets generated by cavitation. Titratable acidity, pH, and °Brix of the cider were not affected by ultrasound treatment. Minor changes in color and turbidity for ultrasound treated samples, especially for sonication at 40°C for 17.7 min, were observed.

Original languageEnglish (US)
Pages (from-to)E102-E108
JournalJournal of food science
Issue number2
StatePublished - Mar 2006


  • Apple cider
  • Cell morphology
  • Escherichia coli
  • Power ultrasound
  • Quality

ASJC Scopus subject areas

  • Food Science


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