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Baking with impingement heating

Identification

Key words impingement, baking, heating, air jet, bread, pizza, cake, cookie, oven
Latest version 2011/12/07
Completed by SP

How does it work?

Primary objective Reduction of baking time and energy consumption
Working principle Baking involves simultaneous heat and mass transport. Heat is transported from the surface into the product and moisture is transported internally towards the product surface and evaporates.

Impingement is a rapid convective heat transfer method. Hot air jets of high velocity are directed towards the product, orthogonally or with an inclination. Different nozzles can be used for adjustment of air jet direction and velocity. The jet disrupts the stagnant boundary gas layer between the product surface and the bulk flow. High air velocity results in a thinner boundary layer and a higher degree of turbulence inside the boundary layer, which improves the heat transfer as well as the removal of moisture from the surface. The heat is further distributed inside the product by conduction and convection (3,4).

The rapid heat transfer achieved with impingement heating gives a faster colour and crust development, as compared to conventional baking, and the baking time can be reduced by as much as 50 %. Also, a lower oven temperature can be used. Colour is developed faster in an impingement oven than in a conventional oven because of the more rapid surface temperature increase. The water loss rate is about the same as for conventional baking, but shorter baking times provides for reduced moisture loss. High moisture retention gives softer crumb and increased shelf life (1,3,4,7).

To achieve even lower energy consumption levels, impingement can be combined with energy efficient baking methods such as infrared or microwave heating.

Images
Additional effects Impingement heating offers space savings, since the ovens are smaller than conventional ovens.
Important process parameters Baking time, oven temperature, impingement air temperature and velocities, impingement nozzle geometry, nozzle-to-product distance, jet orientation.
Important product parameters Product structure and geometry, product composition, moisture content.

What can it be used for?

Products Bread, pizza, cakes, cookies and other baked products.
Operations Baking
Solutions for short comings Conventional baking is a time and energy consuming process. Impingement heating can speed up the process and is more energy efficient.

What can it NOT be used for?

Products Products that require long baking times to allow for desired chemical and physical conversion to take place, for example flavour and texture components, may be difficult to adapt to fast impingement methods.

Products that are sensitive for the distortion from the air jet.

Operations Impingement can be used in all baking operations.
Other limitations In impingement heating the crust cannot reach a higher temperature than the air temperature, as is possible with other baking techniques (3).
Risks or hazards Observe normal safety regulations when working with hot ovens.

Implementation

Maturity Impingement ovens are available at the market. The first impingement oven was patented in 1975. Impingement ovens are common for pizza making.
Modularity /Implementation Impingement ovens can be inserted in an existing production line. Impingement nozzles can be added as a complement in for example IR and microwave ovens.
Consumer aspects Impingement heating is a form of conventional convective heating, which has been used for long time and is well accepted.
Legal aspects Please check local legislation.
Environmental aspects Impingement baking uses less energy than conventional baking.

Further Information

Institutes SP, DIL, TTZ
Companies Buhler Aeroglide
References 1. Li A. and Walker E. (1996). Cake baking in conventional, impingement and hybrid ovens. Journal of Food Science 61(1): 188-191, 197.

2. Olsson E.E.M., Trägårdh A.C., Ahrné L.M. 2005. Effect of near-infrared radiation and jet impingement heat transfer on crust formation of bread. Journal of Food Science 70 (8), E484-E491.

3. Olsson E. 2005. Jet impingement and infrared heating of cylindrical foods. PhD thesis. Department of Food Technology, Engineering and Nutrition, Lund Institute of Technology, Lund University, Sweden.

4. Ovadia D.Z., Walker C.E. 1998. Impingement in food processing. Food Technology 52(4), 46-50.

5. Sumnu G., Datta A.K., Sahin S., Keskin S.O., Rakesh V. 2007. Transport and related properties of breads baked using various heating modes. Journal of Food Engineering 78, 1382-1387.

6. Zhang J., Datta A.K. 2006. Mathematical modeling of bread baking process. Journal of Food Engineering 75, 78-89.

7. Wählby U., Skjöldebrand C., Junker E. 2000 Impact of impingement on cooking time and food quality. Journal of Food Engineering 43, 179-187.



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Created by WikiSysop on 28 February 2012, at 13:09