Microwave (and RF) Heating in Food Processing Applications

Transcription

1 Microwave (and RF) Heating in Food Processing Applications Juming Tang, Ph.D. Professor of Food Engineering Department of Biological Systems Engineering Washington State University, Pullman WA

2 OUTLINE 1. Microwave and Radio Frequency (RF) Heating Principles 2. Established Applications in Food Processing 3. Development of Microwave Sterilization Technology for Pre-packaged Foods

3 SPECTRUM Electromagnetic Spectrum The wavelength l = c/f with c = m/s RF MW l MHz(+/- 0.05%) MHz (+/- 0.6%) MHz (+/- 0.05%) f 915 MHz 2450 MHz Domestic Ovens GHz (plasma) Very restricted bands Can be used for ISM applications

4 Magnetron Generation of microwave

5 Waveguide Magnetron Microwave cavity (applicator) Domestic Microwave Oven (2450 MHz)

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7 Microwave Cooking of Meat Patties (APV system)

8 RF Heating Systems Food

9 Plate Electrodes in RF Heater

10 Industrial Applications of RF Technology - typical up to 85 kw per module Food Dryer Source: Strayfield, UK

11 Dielectric heating of foods - Product temperature in electromagnetic field: C p T = t - Dielectric property: 11 2 '' f E Dielectric constant Loss factor - Contributions of dipole rotation and ionic conduction:

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

13 Single - mode Systems TM010 cavity resonator, 915 MHz (adopted from Regier and Schubert)

14 How Does RF or Microwaves Heat Foods? Alternating Electric field Space charge polarization Orientation polarization

15 Mechanism of Dielectric Heating RF MW Ref: Tang et al., 2002, Scientific Press, New York

16 Penetration Depth (mm) RF Microwaves Ref: Wang et al.,2003. J. Food Eng. 57:

17 2. Industrial Microwave (MW) and Radio Frequency (RF) Technologies -- Better quality -- Reduced process times -- New products?

18 MW COOKING DESSERTS Cooking of desserts in pots Microwave Tunnel Pots / hour Power : 144 KW.

19 MW COOKING/PASTEURIZATION OF VEGS Nutripack (a French Company) solution with valve Valvo-Pack TM The valve allows a thermal treatment and the cooling of the product in the packing without counter-pressure. The valve is adhesive and is installed on the upper part (heat sealing film, cover ) of a packing (plastic, metal, paper, cardboard) that has been previously pierced. Opening limit : 10 mbar 3 mbar Closing limit : 5 mbar 2 bars

20 A similar concept developed by MicVac, Sweden From their website: MicVac develops, markets and sells two methods for processing and packaging convenience food. Both solutions (for pasteurised and unpasteurised foods respectively) use a valve that offers several benefits for both the producer and the consumer. The MicVac method is based on the principle of cooking and pasteurising food using microwaves directly in the sealed consumer package. The film cover on the package has a valve that opens during cooking, releasing the overpressure in the form of steam and oxygen. After cooking, the valve closes and a natural vacuum is created in the package another of the product s many advantages.

21 MW COOKING/PASTEURIZATION EXAMPLES OF PRODUCTS

22 Wokingham, UK RF Finish Drying of Bakery Products 50kW RF Post Baking Unit - Courtesy of Fox s Biscuits, UK

23 Moisture % BDW Moisture profile at exit of an industrial bakery oven, and after RF drying for 5 mins 2.05 Before RF After RF At Packing Working Side Middle Non-working Side

24 RF Post-Baking Virtually Eliminates Checking!

25 Sponge Products Reduces Mold Spores Increases Shelf Life Increases Production

26 Appetisers snack Meringue Puff pastry Breakfast cereal Bread crouton Sponge product Pretzel Short bread Profiterole RF DRYING OF BAKERY PRODUCTS

27 Manufacturers using RF Heating and Drying Kraft (Nabisco) (USA) United Biscuits (UK) Kelloggs (Keebler) (USA) Fox s Biscuits (UK) Weetabix (UK, Canada) Arnotts (Australia/ New Zealand/ Indonesia National Biscuits (S.Africa) Safeway (USA) Ferrero (Italy) Dancake (Portugal) Ulker (Turkey) Pepperidge Farms (USA) M&M Mars (USA) Parle (India) Britannia (India) Crown (Korea) Horizon Biscuits (UK) United Biscuits/Danone (Lu France, Bagley Argentina) Tong Yang (Korea) Morinaga (Japan) Dare Foods (Canada/USA) Barilla (Italy) ETI (Turkey) Ralston Purina (Bremner) (USA) Griffin (New Zealand) Approximately 500 RF food processing systems sold over 37 years

28 3. Development of Microwave Sterilization Technology for Pre-packaged foods (~50 years) All past MW sterilization systems used 2450 MHz

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

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

31 Microwave pasteurization equipment with module open to show alternating placement of magnetrons (Berstoff, 1992)

32 Microwave pasteurization line for prepared meals (Berstoff, 1992)

33 Microwave sterilization unit with external covering removed (overpressure of 2.5 bar,omac, 1992)

34 Continuous microwave sterilization system (OMAC, 1992)

35 Otsuka plant in Japan (2008)

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39 TOP S FOODS Olen, Belgium (2000)

40 The 2nd generation Microwave Sterilization System2000

41 The 3d Generation of Microwave Technology at Tops Foods, 2004

42 Sterilized products produced by TOPS Foods

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

44 4. Research on Microwave Sterilization Technologies at Washington State University

45 4. Engineering and Scientific Challenges in Developing MW Sterilization Processes 1. Technology/systems to provide stable electromagnetic field patterns with high energy efficiency Single mode, high coupling efficiency 2. FDA Approval Stability of system and processes Scientific base/means for process development Food Safety 3. High quality foods 4. Scaling-up and economic viability

46 MW STERILIZATION CONSOTIUM (2001-) Washington State University Microwave Company: Ferrite Component, NH Food Packaging Companies: Rexam Container, MO Graphic Packaging, CO Food Processing Companies: Kraft Foods, ILL Hormel, MN Technical Consultant: NPA Masterfoods (MARS USA), CA Ocean Beauty Seafood Inc., WA Supported by DoD DUST Program and US Army Natick Soldier Center

47 Development of Microwave Sterilization Technology Computer simulation System development Microbial studies Process development FDA Approval Scaling-up Industrial implementation

48 0 phase shift cavity waveguide

49 WSU 915 MHz Single-Mode 10 kw Pilot Scale Sterilization System ( )

50 Steps involved in identification of cold and hot spots with mashed potato sample M-2 Kinetics Fo vs M-2 yield relationship Computer vision to measure M-2 color of processed trays. Checking repeatability of hot and cold spots with different tray sizes and level of salt Identification of cold/ hot location For different tray size. Verification of location Using fiber optics probes

51 77 min heating time (steam at 247 F) parameters MW sterilization of salmon April 15, 2003 (Run-1) 140 circulating water tempture temperature of salmon MW heating: 2.4 min; Total processing time: 10 min. F0= time [min]

52 Shear force (N) Change of Shear Force in Pink Salmon Fillet Heated at 121 C Cooking time (min)

53 Eggs

54 Mashed Potato

55 Microwave sterilized salmon and fried rice

56 Maximum and minimum C values for food in a 10 oz tray after a F0=6 process, water temp=121 C Ideal Retort Process time (min) Max cook value Microwave Min Cook value C values for food in a 10 oz tray after a F0=6 process, water temp =125 C Process time (min) Max cook value Min Cook value Ideal Retort Microwave

57 Sensory and self-life studies at US Army Natick Soldier Center 50 trays chicken were produced for Natick in January 2004 Chicken product: Natick evaluation, shelve study and taste panels

58 Hedonic score (1-9 scale) Chicken Breast, OVERALL Acceptability Averages over 6 months storage at 100 o F Months in 100 o F Storage y = x R 2 = (Microw ave) y = x R 2 = (Retort) Microwave Retort Linear (Microwave) Linear (Retort)

59 WSU 2 nd generation system developed for FDA approval - four single mode cavities, 40 kw max MW power

60 Potential applications for microwave sterilization/pasteurization technologies - new processes - new products - new markets For more information

61 MW and RF Technologies are much more complicated than conventional methods. Successful development of new applications requires extensive R&D efforts based on good understanding of MW and RF heating principles and the systems. Pilot-scale studies are necessary for scaling up to industrial processes

62 Thank You