UVM Theses and Dissertations
Format:
Print
Author:
D'Amico, Dennis John
Dept./Program:
Nutritional and Food Sciences
Year:
2004
Degree:
M.S.
Abstract:
Fresh, unpasteurized milk and fruit juices are appealing to many consumers due to their distinct flavor characteristics and nutritional benefits. Outbreaks of foodborne illness associated with apple cider and dairy products have prompted research on the survival of Escherichia coli 0157:H7 and Listeria monocytogenes in these food systems, respectively. Current processing methods utilize heat for bacterial inactivation; and although effective, these applications may cause undesirable changes in the nutritional and sensorial properties of foods. Non-thermal processing technologies are emerging as promising alternatives.
Ultrasound induced cavitation is lethal to many bacteria, especially when combined with other microbial reduction strategies such as heat. A 400W ultrasound generator was used to evaluate the effects of batch and continuous flow ultrasonic treatment with and without mild heat on the natural flora and Listeria monocytogenes in milk, and E. coli 0157:H7 in apple cider. Continuous flow ultrasound treatment, when combined with mild heat (57°C) for 18 minutes, resulted in a 99.999% reduction of 1. monocytogenes inoculated in UHT milk, 99.999% reduction in total aerobic bacteria in raw milk, and 99.999% reduction in E. coli 0157:H7 inoculated in pasteurized apple cider. Microstructural analysis revealed ultrasound processing results in the reduction of fat globule size as well as protein lipid interactions that may be favorable.
Ultrasound induced cavitation is lethal to many bacteria, especially when combined with other microbial reduction strategies such as heat. A 400W ultrasound generator was used to evaluate the effects of batch and continuous flow ultrasonic treatment with and without mild heat on the natural flora and Listeria monocytogenes in milk, and E. coli 0157:H7 in apple cider. Continuous flow ultrasound treatment, when combined with mild heat (57°C) for 18 minutes, resulted in a 99.999% reduction of 1. monocytogenes inoculated in UHT milk, 99.999% reduction in total aerobic bacteria in raw milk, and 99.999% reduction in E. coli 0157:H7 inoculated in pasteurized apple cider. Microstructural analysis revealed ultrasound processing results in the reduction of fat globule size as well as protein lipid interactions that may be favorable.