Thesis
Process validation and hyperspectral imaging of common foodborne pathogens
Washington State University
Master of Science (MS), Washington State University
05/2021
DOI:
https://doi.org/10.7273/000004267
Handle:
https://hdl.handle.net/2376/125068
Abstract
Validation of preventative control processing steps against pathogens in specific food matrices, and development of affordable methods for rapid pathogen identification are vital aspects of food safety research. Therefore, the first objective of this study was to validate the brownie baking step for controlling Salmonella and Listeria monocytogenes, and to determine the thermal inactivation parameters. For baking validation, brownie batters were prepared from inoculated flour, and baked in the oven set at 350°F (176.7°C) for 40 min followed by 15 min of ambient air cooling. At the end of baking, Salmonella and L. monocytogenes populations in brownies decreased by 6.3 and 5.9 log CFU/g, respectively. For calculating D-values, brownie batter was transferred into thermal-death-time disks, sealed and placed in hot-water baths set at specific temperatures for predetermine time intervals. D-values of Salmonella and L. monocytogenes cocktails in brownie batter were 53.4 and 37.5 min at 64°C, 27.2 and 16.9 min at 68°C, 10.7 and 9.1 min at 72°C, and 4.6 and 7.3 min at 76°C, respectively. The z-values of Salmonella and L. monocytogenes cocktails in brownie batter were 11.1 and 16.4°C, respectively. This study can be used as a supporting document for the validation of similar brownie baking processes to control Salmonella and L. monocytogenes. The second objective of this research was to develop an affordable hyperspectral imaging system and evaluate the efficacy to identify single and mixed strains of E. coli O157:H7 and L. monocytogenes in growth media, and dairy products (whole milk, cottage and cheddar cheeses). Images were captured at 2,000 × magnification on a custom-designed HSI system at wavelengths of 400 nm to 1100 nm with 5 nm band intervals. For each image, 3-cells were selected as regions of interest (ROIs) to obtain hyperspectral signatures of respective bacteria. With the implementation of k-nearest neighbor (kNN) (k = 3), cells were classified by their hyperspectral signatures as E. coli O157:H7 or L. monocytogenes with accuracies of 58.97% and 61.53%, respectively. This preliminary work on the affordable custom-designed HSI system shows great promise for the rapid identification of foodborne pathogens in a variety of dairy food matrices.
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Details
- Title
- Process validation and hyperspectral imaging of common foodborne pathogens
- Creators
- Phoebe Unger
- Contributors
- Minto Michael (Advisor) - Washington State University, Food Science, School of
- 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
- Identifiers
- 99900896414601842
- Language
- English
- Resource Type
- Thesis