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Surface pasteurisation with infrared heating

Identification

Key words surface pasteurisation, infrared heating, in-package pasteurisation, meat product, hot dog, nut, egg, fruit, vegetable, baked product, bakery goods
Latest version 2011/11/17
Completed by SP

How does it work?

Primary objective Fast and energy efficient surface pasteurisation of solid foods.
Working principle When using Infrared (IR) radiation, with a short penetration depth, almost all energy is converted to heat at the surface of the food. IR radiation does not destroy microorganisms directly, but by increasing the surface temperature microorganisms are destroyed by conventional thermal mechanisms. In most solid foods internal heat conduction is poor and IR can therefore be used to increase the surface temperature enough for desirable microorganism reduction without causing substantial increase in interior temperature. A holding time may be applied to ensure sufficient microbial reduction. IR treated products can be directly fed to a packaging machine. Products may also be surface pasteurised after packaging. The effectiveness of infrared surface pasteurisation is comparable to other methods (4,7).
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Additional effects IR may cause surface browning of the products, for example in meat products (4,5).
Important process parameters IR intensity, IR wavelength (longer wavelength has short penetration depth and most of the energy is converted to heat at the surface. Shorter wavelength give a fast heat transfer and has a longer penetration depth which allows reduction of microorganisms located below the surface), temperature, processing time (9).
Important product parameters Food composition and geometry, food surface characterisitics (emissivity), heat conductivity in the food, IR penetration depth, microbial flora, water activity (aw) – a reduction in aw increase the heat resistance of microorganisms (9).

What can it be used for?

Products Solid foods such as ready-to-eat meat products, nuts, almonds, baked products such as sponge cake and bread, spices, shell eggs, fruits and vegetables.
Operations Surface pasteurisation of solid foods.
Solutions for short comings Contamination of foods by spoilage or pathogen bacteria is a severe problem. For example in the production of ready-to-eat meat products, microorganisms may be completely inactivated during production, but post-processing recontamination often occurs. Recontamination primarily occurs on the surface area and superficial heating is a good way to destroy contaminating microorganisms without unnecessary heating of the whole product (4).

With conventional surface pasteurisation methods a heating medium is needed, such as hot air, hot water or steam. A lot of energy is needed to warm up the heating medium. If heat transfer is slow the pasteurisation time will be long, possibly exposing the product to unnecessary long heating times. Hot water pasteurisation implies risks with contaminated heating water and waste water management (8,10). For fruits and vegetables, detergents and disinfectants are commonly added to the pasteurisation water (11). Steam pasteurisation increases the moisture content in the product, causing quality problems in some products (1). IR, on the other hand, is a fast and energy efficient heating method. Shorter pasteurisation times reduce the risk of over-processing of the product. No heating medium is needed, avoiding risks with contaminated water and eliminates the need for chemicals.

What can it NOT be used for?

Products Products that need bulk pasteurisation, since IR pasteurisation mainly is an advantage for surface pasteurisation.
Operations IR pasteurisation is good when a high temperature at the surface is needed. The penetration depth is low, and if it is desired to heat deeper into the products other methods may be preferable.
Other limitations Depending on the geometry of the food, the IR lamps have to be carefully placed in order to achieve uniform heating, and to avoid burning of the surface.

Due to shadow not all surface is treated. The time to reach the desired pasteurisation temperature can be very short using IR. Holding times may be needed to inactivate microorganisms.

Risks or hazards Observe safety regulations when using infrared ovens. Exposure to infrared radiation can produce heat damages and may give chronic adverse effects on the eyes and skin.

Implementation

Maturity IR heating is a mature industrial technology and has been widely used in many industrial applications.
Modularity /Implementation IR equipment can be inserted in an existing production line. In-package surface pasteurisation is possible for some products.
Consumer aspects IR heating has been used in the restaurant business for the last 25 years. However, consumers may be sceptic towards IR heating, as it sometimes is assumed to be the same as irradiation of foods, which may be regared as negative due to assumed health effects (2,6).
Legal aspects EU legislation: directive 2004/40/EC exposure to electromagnetic fields (protection of workers).
Environmental aspects IR surface pasteurisation is more energy efficient than conventional methods. IR can be a substitute to chemicals used for example in surface pasteurisation of fruits and vegetables.

Further Information

Institutes SP, KU Leuven MeBioS
Companies Ircon
References 1. Bingol, G., Yang, J., Brandl, M. T., Pan, Z., Wang, H. and McHugh, T. H. (2011). Infrared pasteurisation of raw almonds. Journal of Food Engineering 104(3): 387-393.

2. De Barcellos M.D., Kügler J.O., Grunert K.G., van Wezemael L., Pérez-Cueto F.J.A., Ueland O., Verbeke W. 2010. Innovative Food Science & Emerging Technologies 11 (4), 721-732.

3. FDA, (2011) Irradiation of Food and Packaging.

4. Huang, L. (2004). Infrared surface pasteurization on turkey frankfurters. Innovative Food Science and Emerging Technologies 5: 345-351.

5. Huang, L. and Sites, J. (2008). Elimination of Listeria monocytogenes on hotdogs by infrared surface treatment. Journal of Food Science 73(1): M27-M31.

6. James, C., Lechevalier, V. and L., K. (2002). Surface pasteurisation of shell eggs. Journal of Food Engineering 53: 193-197.

7. Sakai, N. and Hanzawa, T. (1994). Applications and advances in far-infrared heating in Japan. Trends in Food Science and Technology 5(11): 357-362.

8. Sawai, J., Sagara, K., Hashimoto, A., Igarashi, H. and Shimizu, M. (2003). Inactivation characteristics shown by enzymes and bacteria treated with far-infrared radiative heating. International Journal of Food Science and Technology 38: 661-667.

9. Staak, N., Ahrné, L., Borch, E. and Knorr, D. (2008). Effects of temperature, pH, and controlled water activity on inactivation of spores of bacillus cereus in paprika powder by near-IR radiation. Journal of Food Engineering 89: 319-324.

10. Tanaka, F., Verboven, P., Scheerlinck, N., Morita, K., Iwasaki, K. and Nicolaï, B. (2007). Investigation of far infrared radiation heating as an alternative technique for surface decontamination of strawberry. Journal of Food Engineering 79: 445-452.
11. Trivittayasil, V., Tanaka, F. and Uchino, T. (2011). Investigation of deactivation of mold conidia by infrared heating in a model-based approach. Journal of Food Engineering 104: 565-570.

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Created by Evelina.tiback on 7 December 2011, at 13:32