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PEF fluid handling system inactivates microbes in apple cider.

Current regulations require fresh apple cider to be heat-pasteurized. Previous research has shown that processing fresh apple cider using pulsed electric fields (PEFs) not only can extend the shelf life of the product, but it can also maintain its fresh flavor.

A new pilot-scale fluid handling system with an energy recovery heat exchanger for PEF processing has been built at The Ohio State University. The system has a greater energy efficiency and is easier to operate than the previous unit. It would be suitable for processing apple cider or other juices if the FDA requirements for microbial reduction are met.

The goal of Ohio State scientists was to evaluate how efficiently this system could inactivate the natural flora and surrogate to pathogens in apple ciders. Fresh apple cider was made by a commercial juice processing system. The cider was incubated at 22 C for three days, or inoculated with L. planetarium before undergoing PEF treatment. A pilot-scale pulse generator provided high-voltage pulses.

In their tests, the researchers applied a PEF field strength of from 32 kV per cm to 20 kV per cm. Treatment time was 44 [micro]s. The holding temperature depended on the PEF field strength. Holding time was 15 seconds. The flow rate was 125 L per hour, and the backpressure used was 40 psi.

The PEF-treated ciders were analyzed for microbial counts by investigators. They found that the extent of microbial reductions for both the incubated and inoculated ciders depended on the PEF field strength and holding temperature. The fluid handling system was able to efficiently inactivate bacteria in apple cider. The treatment of 32 kV per cm at 70 C yielded a 5-log reduction of aerobic bacteria and a 5-log reduction of mold and yeast in the incubated cider. In addition, 5 logs of L. planetarium were inactivated in the inoculated cider. No recovery was found during one week's storage at 4 C.

Further information. Howard Zhang, Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Rd., 233 Parker Food Science Building, Columbus, OH 43210; phone: 614-688-3644; email:
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Publication:Microbial Update International
Date:Apr 1, 2006
Previous Article:Chlorine, chlorine dioxide kill spores on apples.
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