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Reading Bakery Systems

How to Bake Crackers by Infrared Radiation?

Infrared radiation is penetrative, up to 4mm in many doughs, depending on the water content and wavelength of the radiation. This radiation bakes the product from the centre, producing the required volume and texture of the biscuit.

When dough pieces for crackers are cut the dough sheet is only 1.3 -2mm thick. Baking to create the structure, texture and volume of the biscuits can only be achieved by infrared radiation. Heating through convection and conduction from the oven band primarily affects the the outside surfaces of the products.

The radiation also reduces the moisture content in the centre of the biscuit, reducing “checking”, hairline cracks in biscuits caused by the moisture gradient between the centre and surface of the product. Infrared radiation is effective in colouring the products, producing good colour contrasts.

Biscuit doughs absorb infrared radiation at wavelengths over 2.5 microns through a change in the vibration of water molecules which causes temperature increase. This radiation is absorbed by the biscuit ingredients.

Food component                     Absorption wavelengths

Water                                         2.7 – 5.0 microns

Sugar                                         3.25 – 3.7 microns

Proteins                                     2.83 – 5.92 microns

Lipids, fats                                 4.4 – 5.76 microns

Snack Crackers

Infrared Heating in Food Processing: An Overview

A model of the baking of biscuits in an indirect fired oven extrapolated to a band oven baking process indicated a heat transfer profile of 45% by radiation, 35% by forced convection and 20% by conduction. Another study of heat and mass transfer in industrial biscuit baking ovens found 69% of heat transfer by radiation, 28% by convection and 3% by conduction. Most studies revealed that radiation was the predominant mode of heat transfer, varying between 50% and 80%.

Cracker structure

Crackers require an open, flaky structure and light crispy texture. This requires a high heat input in the first one third of the oven. The heat input is provided by radiation from the Direct Gas Fired oven zones and conduction from the pre-heated Compound balanced Weave band.

The first zones have minimum extraction and no convection. Humidity is important and the initial temperature rise of the dough pieces is faster with a moist atmosphere.  In a Direct Gas Fired oven about 30% of the humidity is from the products of combustion. Steam may also be applied at the oven feed end.

The surface of the dough pieces must remain flexible to lift and achieve the required volume and thickness of the cracker.
crackers dough sheet

Three layer crackers

Moisture content

Cracker doughs have a high percentage of water, approximately 20 - 25 % of the total dough weight. The moisture is removed in the middle and final zones of the oven.

The moisture content will be reduced to 1.5 – 2.5% of the product weight. This requires the evaporation of approximately 200 g of water for every kg of cracker baked. The evaporation of the water requires a high heat input. The cracker oven will have a high heat rating based on the radiant heat transfer and conduction from the pre-heated oven band

With infrared radiant heat transfer the moisture is removed from the centre of the dough pieces achieving a more even moisture content from the centre to the surface of the product. This is important in reducing “checking”, cracking of the biscuits after packaging.

Heat transfer in the middle and final zones of the oven can be enhanced by the turbulence system.

Colour

Radiant baking in the final oven zones is essential to achieving colour contrast for the crackers to show darker blisters and a pale background.

Colour Creckers

Proces manual for vegetable crackers

Oven specification: Soda crackers

Soda crackers Oven specification

Direct Gas Fired Oven with turbulence and pre-heated Compound Balanced Weave band.

Baking time: 2.5 min
Oven set temperatures: 300/300/280/250

Baker Pacific Direct Gas Fired oven

Baker Pacific Direct Gas Fired oven

Proposed profile for soda crackers DGF

Proposed baking profile for soda cracker oven DGF
Proposed heat ratings for soda cracker oven
Proposed heat ratings for soda cracker oven

Lamination process in fermented crackers

Discussion

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References

1. Almond Noel, 1989, Biscuits, Cookies and Crackers, Volume 2, The Biscuit Making Process, Elsevier Applied Science Publishers Ltd.

2. Broyart B., Trystram G. 2002, Modelling heat and mass transfer during continuous baking of biscuits, Journal of Food Engineering

3. Chavan R.S. and Chavan S.R, 2010. Microwave Baking in Food Industry: A Review. International Journal of Dairy Science, 5: 113-127.

4. Engineering Toolbox, Radiation Heat Transfer, <www.EngineeringToolBox.com>

5. Fahloul, D., et al. 1995. “Measurements and Predictive Modelling Of Heat Fluxes In Continuous Baking Ovens.” Journal of Food Engineering, vol. 26

6. Food Science and Food Safety, Infrared Heating in Food Processing: An Overview, Vol 7, 2008.

7. Hightech Europe, 2011. Baking with Infrared Heating.

8. Institute of Food Technologists. Infrared Heating in Food Processing, Comprehensive Reviews in Food Science and Safety, Vol.7, 2008

9. Journal of  Culinary Science and Technology, 6(2-3) 105-118, 2008. Effect of Far-Infrared Oven on the Qualities of Bakery Products. www.researchgate.net

10. Kerone. Industrial Heating System for Biscuit and Cookies Baking, 2016. www.kerone.com

11. Koral T.  Radio Frequency Heating and Post Baking.

www.strayfield.co.uk

12. Mihalos M. New Food Magazine. Effect of Oven Modes on Baking Unit Operations. Russell Publishing, United Kingdom.

13. Molecules, A comprehensive review on Infrared Heating, 2019, 24, 4125.      

www.mdpi.com

14. Monga A. Radio Frequency Applications in Bakeries.

www.strayfield.co.uk

15. Shiffmann R.F.  Microwave Technology in Baking. 1993, Springer Boston.  www.springer.com

16. Wade P. Biscuit Baking by Near Infrared Radiation, J. Food Eng. 1987, 

6, 165-175

Kathiravan Krishnamurthy Harpreet Kaur Khurana Jun Soojin Joseph Irudayaraj Ali Demirci

Leading image by Nataliya Arzamasova/shutterstock.com

Biscuit,crackers

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