Dissertation
SORPTION ISOTHERMS OF HIGH SUGAR CONTENT PRODUCTS AND THEIR INFLUENCE ON THERMAL RESISTANCE OF SALMONELLA
Doctor of Philosophy (PhD), Washington State University
01/2020
Handle:
https://hdl.handle.net/2376/117380
Abstract
Recent foodborne outbreaks in low-moisture foods were caused mostly by Salmonella and its thermal resistance is influenced by changing water activity. Still, there is a lack of the information in how water activity change when temperatures change in low-moisture high-sugar products. The objectives of this study were to: 1) determine the effect of temperature on water activity in low-moisture high-sugar products, 2) determine the survivable of Salmonella Enteritidis PT30 and Enterococcus faecium in high fructose corn syrup and honey using different inoculation methods, and 3) identify the thermal resistance of Salmonella Enteritidis PT30 in sugar products at 80 °C at low aw levels. Firstly, in honey the equilibrium moisture content for aw<0.50 decreased as temperature increased. In honey powder, fructose, and glucose, there was a sharp increase in the equilibrium moisture content with increasing temperature, except, at 20 °C for glucose, for which no water was adsorbed in the whole water activity range. The water activity-dependent breakage points of sugars’ crystalline structure decreased with increasing temperature. Secondly, the results showed that both inoculation methods, S. Enteritidis and E. faecium were unable to survive in honey, and greater than 6-log reductions of bacterial population during the a 4-week storage at room temperature (~22 °C). There was no significant difference (p>0.05) in the inactivation rate between the organisms based on inoculation method. Thirdly, two pure sugars (glucose and fructose) and honey powder were selected for this research. Results showed that the D80 °C -values of S. Enteritidis PT30 decreased with increasing aw of all samples. At aw80 °C 0.18, Salmonella Enteritidis PT30 in glucose powder has higher D-value than those in fructose and honey powder whereas, at aw80 °C 0.30, 0.40, and 0.50, Salmonella Enteritidis PT30 in fructose powder has higher D-values than glucose and honey powder at 80 °C. The Zaw values of S. Enteritidis PT30 in fructose and honey powder are comparable while different in glucose because of the phase change. The results of this study provide insights on understanding the thermal resistance of Salmonella in sugar and guidance on thermal process design to improve the safety of low-moisture high-sugar products.
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Details
- Title
- SORPTION ISOTHERMS OF HIGH SUGAR CONTENT PRODUCTS AND THEIR INFLUENCE ON THERMAL RESISTANCE OF SALMONELLA
- Creators
- Jaza Maqbl Alshammari
- Contributors
- Juming Tang (Advisor)Shyam Sablani (Committee Member)Meijun Zhu (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Systems Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 131
- Identifiers
- 99900581703901842
- Language
- English
- Resource Type
- Dissertation