Thesis
Salmonella resistance against cinnamon oil, desiccation and heat in paper disc with or without almond surface components
Washington State University
Master of Science (MS), Washington State University
2017
Handle:
https://hdl.handle.net/2376/103295
Abstract
Cinnamonum cassia oil was tested for its antimicrobial effect against outbreak strains Salmonella Enteritidis PT30 and Salmonella Tennessee K4643. Death curves showed that including 0.1% and 0.15% (v/v) C. cassia oil resulted in ∼7 Log reduction of bacteria within 2 h. However, the antimicrobial efficacy of cinnamon oil was reduced when S. Enteritidis PT30 was established on almonds/paper discs, 0.4% C. cassia oil only resulted in ∼1.7 Log10 CFU/almond or 3.2 Log10 CFU/disc reduction within 2 h, respectively. S. Enteritidis PT30 established on both almonds and paper discs were stable, and only had 0.80 Log10 CFU/almond and 1.20 Log10 CFU/disc reduction during 9-week and 7-week storage at room temperature, respectively. Cinnamon oil intervention increased S. Enteritidis PT30 reduction in both almonds and paper discs during storage. 0.4% cinnamon oil treatment reduced S. Enteritidis PT30 on paper disc to undetectable level within 4 weeks, but only led to 2 Log10 CFU reduction on almonds, indicating a protection effect from the almond matrix or almond surface components. Almond washed solution (AWS) enhanced thermal resistance of S. Enteritidis PT30. Dvalues of S. Enteritidis PT30 on paper disc with AWS were 23.5±0.9, 18.7±2.7, and 6.7±1.1 min at 80°C, 85°C, and 90°C, respectively, which is higher than those in paper discs (14.5±1.3, 8.7±0.9, and 4.1±0.8 min). Expressions of sigma factors as well as genes related to desiccation and thermal resistance were evaluated. mRNA expression of rpoE, H and S were significantly increased under desiccation, however, no change at protein levels. Interestingly, protein levels of RpoE & RpoH, but not RpoS, were decreased when desiccated with AWS while the mRNA expressions of all 3 sigma factors remain at similar levels compared to unstressed control Salmonella. In addition, mRNA expression of 5 membrane related genes and 2 sRNA for OMPs regulation, as well as selected heat chaperones, were all enhanced under desiccation but not desiccated with AWS. In conclusion, C. cassia oil is effective against Salmonella, but its antimicrobial efficacy against Salmonella was compromised by desiccation and food matrix. In addition, AWS exerting a protect role in desiccant and heat with an unidentified mechanism(s).
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Details
- Title
- Salmonella resistance against cinnamon oil, desiccation and heat in paper disc with or without almond surface components
- Creators
- Hseih-Chin Tsai
- Contributors
- Meijun Zhu (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, Washington] :
- Identifiers
- 99900525162601842
- Language
- English
- Resource Type
- Thesis