Thesis
Using Fourier transform infrared (FT-IR) spectroscopy in the detection of sublethal injured Listeria innocua by acetic acid
Washington State University
Master of Science (MS), Washington State University
2011
Handle:
https://hdl.handle.net/2376/103114
Abstract
A single strain of Listeria innocua, ATCC 33090, was treated in saline (0.9% NaCl) with 1% (pH=2.58) or 0.5% (pH=2.77) acetic acid or in tryptic soy broth with 0.6% w/v yeast extract (TSBYE) with 1% (pH=4.13) acetic acid for selected times. For the three acid treatments, no significant differences were found in bacterial counts on either PALCAM or tryptic soy agar with 0.6% yeast extract (TSAYE) agar, which indicated that no sublethally injured cells were present. Survival curves for all three treatments showed a biphasic shape which indicated that populations of L. innocua are composed of cells with different levels of sensitivity to acetic acid. Fourier Transform Infrared (FT-IR) spectroscopy was applied to analyze L. innocua cells treated in TSBYE with 1% acetic acid to determine what effect treatment with acetic acid had on intracellular macromolecular constituents. FT-IR spectra (1800-900 cm-1 ) showed changes in bands for proteins, lipids, DNA/RNA and carbohydrates occurred between the control (no acid added, at 0 h) and 51 h treatment, indicative of structural damage to cell walls, cell membranes, DNA/RNA, flagella, teichoic acids and to cytoplasmic proteins. Five multivariate statistical methods (principal component analysis (PCA), soft independent modeling of class analogy (SIMCA), k-nearest neighbors algorithm (kNN), partial least squares discriminant regression (PLSR) and hierarchical classification analysis (HCA) were applied and successfully classified spectra of bacteria treated for selected time intervals (control, 3 h, 9 h, 21 h and 51 h) indicating the potential FT-IR spectroscopy has for analyzing organic acid-stressed Listeria spp.
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Details
- Title
- Using Fourier transform infrared (FT-IR) spectroscopy in the detection of sublethal injured Listeria innocua by acetic acid
- Creators
- Di Wu
- Contributors
- Barbara Rasco (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Food Science, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525161001842
- Language
- English
- Resource Type
- Thesis