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Development of a Chlorine Dioxide Gas Concentration Monitoring Unit and Kinetic Analysis of the Effect of Chlorine Dioxide Treatment on Color and Microbial Content Change of Spinach

Gehringer, Ryan Anthony

Abstract Details

2013, Master of Science, Ohio State University, Food, Agricultural and Biological Engineering.
Analytical methods for measuring chlorine dioxide concentration in solution have been extensively researched and documented in literature. Much less common, are the techniques for measuring ClO2 in a gaseous medium, particularly when the measurement is needed to be made continuously in real time. While acceptable spectroscopic methods are known, complications arise due to the variability of the molecular absorption cross section which must be known to determine the concentration present. Depending on the wavelength being used and the temperature of the medium, the molecular absorption cross section changes. The purpose of this study was to develop an inexpensive and robust measurement device that would accurately measure ClO2 in real time. Without the ability to obtain highly specified light output and detection devices, extensive calibration was needed to assure the raw measurement was properly converted into a true concentration. The resolution of the device also needed to be adjusted so that the ClO2 concentration could be determined with a high level of accuracy throughout the concentration range of interest between 1-5 mg/l. With the aid of a spectrophotometer as a means of calibration, a measurement device was developed using only a light emitting diode (LED) and a photodiode as the major components. Through several iterations the device was adjusted to obtain a measurement precision of ¿¿ 0.19 mg/l and a minimum resolution of 0.05 mg/l over the desired measurement range. The device was also shown to be capable of withstanding repeated exposure to environments containing ClO2 concentrations between 1-12 mg/l for exposure times of over an hour without deteriorating the measurement capabilities of the instrument. The development of a ClO2 measurement device for accurate concentration determination is essential for the application of ClO2 gas for sanitation of fresh produce on an industrial scale. Fresh produce safety, especially for leafy green vegetables, has become a focal point of interest in recent years. In an effort to reduce microbial loads present on fresh produce, gaseous sanitizers are being explored because of their higher diffusivities. In this study, spinach was exposed to chlorine dioxide (ClO2) gas, in an effort to determine concentration and exposure time combinations which yield maximum microbial reduction while causing minimal color change to the leaf. An extensive study was first performed to determine the color change, quantified as the change in hue angle, by varying ClO2 concentrations (2.0-6.0 mg/L) and exposure times (0.5-24 min). The resulting data were organized in form of a state diagram to determine the acceptable and unacceptable product in terms of color as a result of ClO2 treatment. On the acceptable regions of the state diagram, ClO2 concentration-exposure time combinations were chosen for microbial inoculation studies. Log reductions as high as 2.27 units were observed while only having a minor effect on the color of the spinach leaves (2.05¿¿0.06 mg/l for 20 min). Kinetic data were collected to determine the rate of microbial reduction and rate of color change of spinach leaves at selected ClO2 concentrations. These results suggested that, in order to completely eliminate color damage, high concentration short-time exposure may be the only practical way to better sanitize fragile food material like spinach. Lengthy exposure times may not provide an additional microbial reduction that is capable of outweighing the additional property damage that long-time exposures cause.
Gonul Kaletunc (Advisor)
George Plum (Committee Member)
Sudhir Sastry (Committee Member)
Ahmed Yousef (Committee Member)
165 p.

Recommended Citations

Citations

  • Gehringer, R. A. (2013). Development of a Chlorine Dioxide Gas Concentration Monitoring Unit and Kinetic Analysis of the Effect of Chlorine Dioxide Treatment on Color and Microbial Content Change of Spinach [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1357333222

    APA Style (7th edition)

  • Gehringer, Ryan. Development of a Chlorine Dioxide Gas Concentration Monitoring Unit and Kinetic Analysis of the Effect of Chlorine Dioxide Treatment on Color and Microbial Content Change of Spinach. 2013. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1357333222.

    MLA Style (8th edition)

  • Gehringer, Ryan. "Development of a Chlorine Dioxide Gas Concentration Monitoring Unit and Kinetic Analysis of the Effect of Chlorine Dioxide Treatment on Color and Microbial Content Change of Spinach." Master's thesis, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1357333222

    Chicago Manual of Style (17th edition)