U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 close



Research
                Research Home
                            National Programs
                            Research Projects
                            Scientific Manuscripts
                            International Engagement
                            Scientific Software/Models
                            Databases and Datasets
                            Office of Scientific Quality Review
            Media
                News & Features
                            Multimedia
                            Briefing Room
                            Down on the Farm
                            Press Room
                            Science in Your Shopping Cart
                            Scientific Discoveries
                            Tellus
                            Under the Microscope
            About ARS
                About ARS Home
                            Staff Directory
                            Labs and Research Centers (Map)
                            Headquarter Offices
                            Organizational Chart
                            Employee Services (REE Employees Only)
                            Office of Outreach, Diversity, and Equal Opportunity
            Work With Us
                Work With Us Home
                            ARS Vacancies at USAJOBS
                            Careers at ARS Information
                            Scientific Collaborations
                            Extramural Agreements
                            1890 Faculty Research Sabbatical ProgramSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Northeast Area Wyndmoor, Pennsylvania Eastern Regional Research Center Food Safety and Intervention Technologies Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            Geveke, Daviditem
                                            Gurtler, Joshuaitem
                                            Zhang, Howard
  Submitted to: Journal of Food Protection
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 10/31/2008
                                    Publication  Date: 1/3/2009
                                    Citation: Geveke, D.J., Gurtler, J., Zhang, H.Q. 2009. Inactivation of Lactobacillus plantarum in apple cider using radio frequency electric fields. Journal of Food Protection. 72(3):656-661.Interpretive Summary: Apple cider has been pasteurized at low temperatures using a novel technology employing radio frequency electric fields (RFEF). However, most of the previous studies on RFEF pasteurization used gram negative bacteria and none used gram positive bacteria. The present study is the first to RFEF process Lactobacillus plantarum, a gram positive bacterium. The population of L. plantarum in apple cider was reduced by 90% following RFEF processing at 50 C. Raising the RFEF temperature to 55 C killed more than 99% of the L. plantarum and injured 94% of the survivors. Refrigerating the cider for 5 weeks killed nearly all of the remaining bacteria.  This provides the first evidence that nonthermal RFEF processing is capable of killing a gram positive bacterium and that the surviving cells die off during refrigerated storage. The results of this study and previous studies point to the possibility of using RFEF processing to pasteurize apple cider containing gram negative and gram positive bacteria.
                                Technical Abstract: Radio frequency electric fields (RFEF) processing is effective at inactivating Gram negative bacteria in fruit juices at moderately low temperatures, but has yet to be shown to be effective at reducing Gram positive bacteria. Lactobacillus plantarum ATCC 49445, a Gram positive bacterium, was inoculated into apple cider and the cider was RFEF processed at the following conditions: field strength 0.15 to 15 kV/cm; temperature 45 to 55 C, frequency 5 to 65 kHz, treatment time 170 microseconds, and holding time 5 to 50 s. In addition, the effect of refrigerating the inoculated cider prior to RFEF processing, the extent of sublethal injury, and the effect of storing the treated cider for 35 d was investigated. The population of L. plantarum in apple cider was reduced by 1.0 log following RFEF processing at 15 kV/cm, 20 kHz, and 50 C with a hold time of 5 s. There is a synergistic effect between RFEF and heat above 50 C. Inactivation significantly (P < 0.05) increased as the frequency was decreased from 65 kHz to 5 kHz. There was little inactivation at field strengths below 8 kV/cm. Above this “critical” level, inactivation increased linearly with increasing field strength. Holding the cider at 55 C following RFEF treatment for 5 and 50 s resulted in reductions of 2.5 and 3.1 log, respectively. The sublethal injury of L. plantarum was 1.4 log. The population of processed L. plantarum cells stored at 4 C steadily and significantly (P < 0.05) declined over a 35 d period from 4.5 log to 0.9 log cfu/ml. The electrical energy density for the RFEF process was 51 J/ml of cider. This provides the first evidence that nonthermal RFEF processing is capable of inactivating a Gram positive bacterium and that the surviving cells die off during refrigerated storage.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov