Radiofrequency: New Technology Applications and Validation of Pathogen Reduction

Transcription

1 Radiofrequency: New Technology Applications and Validation of Pathogen Reduction Soon Kiat Lau, Doctoral Student Jeyam Subbiah, Ph.D., P.E. Kenneth E. Morrison Distinguished Professor of Food Engineering Biological Systems Engineering and Food Science & Technology (402)

2 Radiofrequency Heating Radiofrequency (RF) heating utilizes radio waves (13.56, 27.12, MHz) to generate heat through: Orientation polarization Ionic conductivity 2

3 Comparison with traditional thermal processing Hot Traditional Heating RF heating Cold 3

4 Comparison with microwave processing Microwave Heating RF Heating 915 MHz 2450 MHz MHz MHz MHz 4

5 Comparison with microwave processing Jiao S. et al Radio-Frequency Heating in Food Processing. G.B. Awuah, H.S. Ramaswamy, and J. Tang (eds.), Boca Raton, FL: CRC Press, Taylor & Francis Group, pp. 6. 5

6 Advantages of RF Heating Suitable for foods with poor thermal conductivity Low-moisture foods e.g. egg white powder (EWP) Oven temperature Center of EWP Center of EWP Hot air oven RF heating 6

7 Advantages of RF Heating Shorter come-up time High temperature, short time processing Beney L. et al Food preservation techniques. P. Zeuthen and L. Bøgh-Sørensen (eds.), Boca Raton, FL: CRC Press, pp

8 Advantages of RF Heating Can be turned on or off instantly Product can be pasteurized after being packaged More energy efficient 8

9 RF assisted thermal processing RF heating Hot air oven 9

10 Mechanisms of inactivation Thermal effect is the essential contributor to the destruction of microorganisms (Goldblith and Wang 1967; Rosén 1972; Fujikawa and others 1992). The general consensus (Heddleson and Doores 1994) is that the reported non-thermal effects are likely to be due to the lack of precise measurements of the time-temperature history and its spatial variations. 10

11 General RF process development D and Z- values Mini quality Validation In-depth quality Determine lethal time and temperature (t & T) combination Identify surrogate Narrow down the choices of t & T combinations e.g. Color Optimize equipment and product design to ensure heating uniformity Microbial challenge Quantify similarity between model and experiments e.g. Fatty acid profile, volatile content 11

12 D and Z- values Mini quality Validation In-depth quality Isothermal Studies Inactivation mechanism is purely thermal. No RF-resistance, only typical thermal resistance. Microbiological methods and surrogates are similar to those used for conventional heating methods. 12

13 D and Z- values Mini quality Validation In-depth quality Mini Quality Studies Narrow down lethal time-temperature combinations Burnt food edible food! E.g. color, peroxide value 13

14 D and Z- values Mini quality Validation In-depth quality Cold spots RF heating is inherently a thermal process Determination of cold spots is essential for process control Cold spots can vary depending on various factors Composition of food Shape of food Frequency of RF applicator Design of RF applicator Time 14

15 D and Z- values Mini quality Validation can pinpoint/reduce the cold spots In-depth quality Shape of food/package affects location of cold spots 15

16 D and Z- values Mini quality Validation can pinpoint/reduce the cold spots In-depth quality W m -3 RF electrode design affects location of cold spots 16

17 D and Z- values Mini quality Validation can pinpoint/reduce the cold spots In-depth quality Visualization of cold spots in continuous RF heating 17

18 D and Z- values Mini quality Material properties collection Validation In-depth quality 18

19 D and Z- values Mini quality Validation (Thermal) Fiber optic sensors Validation In-depth quality 19

20 D and Z- values Mini quality Validation In-depth quality Validation (Microbial) Inoculation and enumeration methods similar to typical thermal treatments. 20

21 D and Z- values Mini quality Validation In-depth quality Validation Challenges Cold-spot may not be always at the geometric center use modeling to identify cold spot location Variations in food composition/properties Affects location of cold spots Collect variability in properties and perform Monte Carlo simulation for sensitivity analysis Identify the properties for the worst-case scenario Monitor and control these properties 21

22 RF process monitoring Voltage or power level Forward and reflected power Electrode gap Product geometry (depth) Residence time (belt speed) Product characteristics (moisture content) 22

23 D and Z- values Mini quality In-depth quality Validation In-depth quality 23

24 Case study: Wheat Flour D values 140 A 120 A D-values (min) B B C C B B D C E E C C EF FG GH H 0 E. faecium Salmonella E. faecium Salmonella E. faecium Salmonella E. faecium Salmonella E. faecium Salmonella E. faecium Salmonella E. faecium Salmonella E. faecium Salmonella E. faecium Salmonella Temperature ( C) Water activity

25 Case study: Wheat Flour and validation 25

26 Shorter come-up time Hot air oven RF heating RF heating Hot air oven 26

27 Case study: Wheat Flour Quality analysis 27

28 Conclusions RF is a thermal process RF is used to reduce come-up time (minimal log reduction); thermal process used is for holding time (most log reduction) RF-assisted thermal processing can be used as a hightemperature, short-time method to retain quality EWP: 56 C for 14 days RF-assisted: 80 C for 16 hours Same validation procedures for thermal processing hold true for RF-assisted thermal processing 28

29 Questions? Jeyam Subbiah, Ph.D., P.E. Morrison Distinguished Professor of Food Engineering University of Nebraska Lincoln Ph: (402) Web: Microwave.unl.edu 29