Microwave Assisted Thermal Sterilization - MATS Showcase January 21, 2015 Bill Wilson, P.E. Washington State University Extension Energy Program 1
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Introduction What we are going to discuss: New process technology for post-packaging processing (sterilization) of low-acid/high-moisture food products resulting in long-term, ambient condition, shelf-stable, food products preservation 3
BPA TI Project Funding Acknowledgement http://www.bpa.gov/doing%20business/technologyinnovation/tipprojectbriefs/2014-tip-261.pdf 4
Microwave Assisted Thermal Sterilization (MATS ) Developed by Dr. Juming Tang s Microwave Group at Washington State University, Pullman Campus affiliated with the Department of Biological Systems Engineering Adaptation of 915 MHz frequency microwave energy for internal heating of food products in their hermetically sealed storage containers to sterilization temperatures
What is Post-Packaging Sterilization? Process for deactivation of microorganisms and their spores. Internal temperatures in excess of 212 o F required (generally 250 265 o F), with adequate holding time once temperature is reached We are all very familiar with conventional post packaged sterilization technologies as food processors, domestic food preservationists, or consumers Examples of products created using conventional technologies and target categories for MATS technology follow. 6
Examples of Post-Packaged Sterilized Products
How is Post Packaging Thermal Sterilization Achieved? Imparting thermal energy to heat container and contents to sterilization temperature For flexible or semi-rigid non-metallic containers in particular must be done in pressurized atmosphere environment to avoid product water content vaporization Most frequently, pressurized atmosphere is steam (15 psig sat. steam ~247 o F), or hot water at sterilization temperature maintained at 20 psig or greater pressure
Attributes of MATS vs. Conventional Technologies Benefits Drawbacks Significant reduction in thermal processing time (1/4 to 1/10 of conventional processing time) Greatly improved product visual and sensory appeal - particularly prepared meals containing delicate ingredients Improved nutrient retention Inherently capable of adaptation to continuous-type sequential processing system design Shelf-stable end-products eliminate refrigeration requirements for processing, warehousing, transportation, retail sales storage/presentation Initial indication of a reduction in processing energy intensity (gross combined process energy consumption/unit mass of product) usually stated as Btu s per lb. of product Processing energy cost/production unit increase due to electrical vs. thermal energy utilization (particularly for natural gas)
Conventional Sterilization Methods Conventional Technologies Steam heated retorts (also called autoclaves ) Water immersion retorts Steam water spray retorts All types Batch operation (most typical) Continuous operation (rare)
Batch-Type Retorts Still Steam Disadvantages Warm-up losses Vent & bleeder losses Product thermal mass Long come-up & cook time Long product cooling time
Batch-Type Retorts Water Immersion (with Water Recovery Vessel) Disadvantages Warm-up losses Long come-up & cook time Long product cooling time
Batch-Type Retorts (Steam Water Spray) Advantages No Steam Venting Loss No Continuous Bleeder Loss Minimal Water Volume Heat-up Disadvantages Warm-up losses Electrical & Compressed Air Consumption
WSU MATS 40 kw Pilot Line
WSU MATS Semi-Continuous 40 kw Pilot Line View: Preheating Section (lower) Microwave Section (Upper) 20 KW 915 MHz Microwave Generators
Summary of WSU MATS Major Milestones July 2001 July 2001 Oct. 2006 Aug. 2007 Oct. 2009 Nov. 2010 Nov. 2010 Dec. 2010 Mar. 2012 Formed WSU Microwave Consortium I Developed first 915 MHz single mode pilot system (10 kw) Received US patent for 915 MHz single mode microwave sterilization system design Developed a second generation system semi-continuous system (40 kw) Received FDA acceptance for MW sterilization of mashed potato in 10 oz. trays Formed MW Consortium II, focusing on commercialization Food Chain Safety (Maple, Valley, WA) is granted license for exclusive rights for commercialization of MATS Technology [Now 915 Labs] Received FDA acceptance for MW sterilization of salmon fillets in sauce in 8 oz. pouches Received non-objection letters from USDA FSIS
Retort Processes Energy Consumption Comparisons Like many Energy Consumption Comparisons It Depends Currently batch or continuous operation? Product temperature increase required Equipment capacity utilization and density of product pack Initial projection of Microwave compared with batch processing indicates favorable energy intensity and overall energy efficiency metrics Energy Intensity??
Commercial Assessment Outcome Summary Energy Intensity, Btu/lb Product 1,400 1,200 1,000 800 600 400 200 0 864 Energy Intensity (As Measured/Estimated) 1,293 Still Steam Immersion w/ Water Recovery 300 260 Steam Water Spray Continuous Rotary Retort (cans) Lb. Product/Ft 3 Usable Retort Volume (As Measured/Estimated) Energy Intensity Product/Volume Ratio 35 32.5 30 Lb/Ft 3 25 20 15 10 7.1 10.4 5 0 Still Steam Immersion w/ Water Recovery Steam Water Spray
Commercial Assessment Outcome Summary Energy Intensity, Btu/lb Product 1,400 1,200 1,000 800 600 400 200 0 Energy Intensity Normalized for Pack Density & Temp. Rise 651 1293 Still Steam Immersion w/ Water Recovery 658 Steam Water Spray 260 Continuous Rotary Retort (cans) Energy Intensity
Input Energy Distribution Input Energy Distribution (As Measured/Estimated) 100% 90% 80% 70% 60% 50% 40% 29.0% 18% 56.2% 79.2% Electrical Product & Container Sensible Heat: Surface Losses Preheating Bleeder Losses 30% 20% Vent Losses 10% 0% Still Steam Horizontal Water Immersion Steam Water Spray Continuous Rotary Retort (cans)
For Additional Information: WSU Microwave Group: www.microwaveheating.wsu.edu Food Chain Safety/915 Labs: www.fcsmats.com Bill Wilson: wilsonb@energy.wsu.edu (360) 956-2041 21
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