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Microwave sterilization, a potential technology for MREs

Microwave sterilization, a potential technology for MREs. Juming Tang, Ph.D. Professor of Food Engineering Oct. 26, 2010 Department of Biological Systems Engineering Washington State University, Pullman WA Microwaveheating.wsu.edu. Target: C. botulinum spores.

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Microwave sterilization, a potential technology for MREs

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  1. Microwave sterilization, a potential technology for MREs Juming Tang, Ph.D. Professor of Food Engineering Oct. 26, 2010 Department of Biological Systems Engineering Washington State University, Pullman WA Microwaveheating.wsu.edu

  2. Target: C. botulinum spores Conventional Retorting Relies on Heat Convection and Conduction in Foods Retort Convection

  3. 2450 MHz microwave heating system for food in plastic pouches at US Army Natick Soldier Center in 1970 A Multi-mode 2450 MHz Microwave Cavity

  4. Sept. 2010, WSU MW Lab.

  5. OUTLINE • Instruction – microwaves • Industrial 2450 MHz multi-mode microwave sterilization systems • Development of 915 MHz single-mode microwave sterilization technology • Examples of MW processed products • A case study for FDA approval – salmon fillet in sauce

  6. 1. Microwave Heating The wavelength l = c/fwith c = 3.108m/s Electromagnetic Spectrum l MW RF l • 915 MHz Industrial (wavelength in free space=0.33 m) • 2450 MHz Domestic Ovens & Industrial Uses (0.12 m) Allocated by FCC for Industrial, Scientific Medical (ISM) applications f

  7. Waveguide • Magnetron • Microwave cavity (applicator) • Domestic Microwave Oven (2450 MHz)

  8. Possible modes for an empty non-cubical microwave oven (Chan and Reader, 2000) • Electric field pattern for (a) TM350 and (b) TE204 • Frequency Spectrum of 2.45 GHz magnetron

  9. Multi-mode Systems Electric field pattern for a loaded microwave cavity at 2.4295 GHz. (Chan and Reader, 2000)

  10. 2. Development of Microwave Sterilization Technology for Pre-packaged foods (>40 years) All past MW sterilization systems used 2450 MHz (~12 cm wavelength in free space)

  11. 2450 MHz microwave heating system for food in plastic pouches at US Army Natick Soldier Center in 1970 A Multi-mode 2450 MHz Microwave Cavity

  12. Tops Foods (Olen Belgium) 3rd Generation 2450 MHz Microwave Sterilization/Pasteurization System (2004)

  13. Sterilized products produced by TOPS Foods

  14. MW pasteurized, processed to 80C shelf-life 35 days at 7C MW sterilized, shelf-life 1 year at room temperature

  15. Major limitations of 2450 MHz systems • Shallow penetration depth (<1cm) – longer heating time • Multi-mode systems, leading to unpredictable and non-uniform heating patterns in foods

  16. 3. Development of 915 MHz Single-Mode Microwave Sterilization/Pasteurization Technology at WSU A. System design to provide stable and predictable electromagnetic field patterns with high energy efficiency Single –mode, high coupling efficiency B. FDA approval for low acids shelf-stable foods Stability of system and processes Scientific base/means for process development Food Safety • Scaling-up and economic viability • Suitable Packaging Materials 14 year activities supported by DoD Dual Use Program (2001-), US Army Natick Solider Center, WSU, USDA NRI Programs, MW Consortium Members, and Print-Pack

  17. WSU Single Mode Design for 915 MHz Microwave Sterilization Systems, patented in 2006 0 phase shift cavity waveguide

  18. WSU 2nd generation system - four single mode cavities, 40 kW max MW power, assembled in 2008

  19. 77 min heating time (steam at 247 F)

  20. Change of Shear Force in Pink Salmon Fillet Heated at 121˚C

  21. Example: 10 oz trays (Rexam containers) containing chicken breast in sauce, processed by the WSU 915 MHz sterilization system for accelerated shelf-life/sensory studies at US Army Natick Soldier Center

  22. Results from sensory evaluations at US Army Natick Soldier Center

  23. Example: Chicken and dumplings in 8 oz pouches (Print-pack) processed with WSU Microwave Sterilization System, produced for sensory studies at US Army Natick Soldier Center • Chicken and dumplings in 8 oz foil pouches by retort (control) for the sensory studies

  24. Promises of Microwave Sterilization Technology: Examples of MW processed products • After MW processing

  25. Microwave sterilized salmon and fried rice

  26. On Oct. 7, 2009, WSU technology received FDA approval for pre-packaged food sterilization using microwave energy, first ever in USA history

  27. On July 18, 2010, the Institute of Food Technologists presented the 2010 R&D Award to WSU Consortium for “contributions to food technology that results in foods of improved quality and nutrition”. Juming Tang (WSU), C. Patrick Dunne (Natick Soldier Center); Douglas Hahn (Hormel), Kenny Lum (Seafood Products Association); and Evan Turek (Kraft ) received the award on behalf of the team

  28. 4. Case Studies- ctivities related to FDA filing of salmon fillets in sauceSept. 2009 - Sept. 2010

  29. Salmon filet, skinless and boneless

  30. 8-oz Printpack pouch

  31. Placement of pouches on mesh belt conveyor and orientation of pouches in MW processing • Moving direction of food pouches:

  32. Cold spot validation with real foods Processing real food in MW system • Data retrieval from Ellab temperature sensor • Positioning Ellab sensor tip at the location determined by heating pattern • Temperature profile overlay with MW system data

  33. Heat penetration data collection

  34. Microbial validation of food safetyTargeted microorganism – C. botulinum spores NFPA strain 3679 (P.A. 3679) as the surrogate. It needs to be 100 times more heat resistant than C. botulinum spores, so that we use smaller number of surrogate to validate at least 12 log reduction in C. botulinum spore populations

  35. Inoculating PA 3679 spores to the cold spot in salmon fillets

  36. Observations Incubation results (after 90 days’ incubation) Control: all 30 unprocessed inoculated control pouches were positive after 1 day incubation; All the 10 un-inoculated pouches processed at each level were negative. • Level-1: 47 out of 50 pouches (94%) were positive (expected:100% positive). • Level-2: 12 out of 50 pouches (24%) were positive (expected 65% positive). • Level-3: No positive (expected 0.041%). • Level-4: No positive (expected 0.0065%). • Level-5: No positive (expected 0.0000041%). Conclusion: The MW process delivered expected lethalities.

  37. Incubation in Walk-in Incubator (~ 36°C) • Positive pouches

  38. Recovery tests after 90 days incubation at 36C 25% of pouches of Level 3 (target) and 25% of negative pouches of Level 2 (under processed) taken for enrichment tests

  39. Recovery tests

  40. Submitted filing for salmon fillets in sauce in 8 oz pouches

  41. FUTURE DIRECTIONS WSU licensed exclusive rights for commercialization of this technology to Food Safety Chain (FSC) corporation (Maple Valley, WA). We are forming a second consortium (Nov. 2, 2010, consortium meeting in Seattle). WSU is expanding the technology to address a broad food safety issues for various entrees and convenient meals, frozen, chilled or shelf stable.

  42. Thank You

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