Infrared

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General Information

Overview

The progress in Infrared technologies is related to the development of applications for sensing, imaging and electronic information and communication technology.

Infrared technology is basically low energy intensity electromagnetic radiation. Therefore, advancements in electromagnetic sciences and technologies are relevant for the development of the technology.

(Kaine-Krolak & Novak,1995)


Advantages

  • High heat transfer performance, reducing processing time and energy consumption with improved quality product. Also potentially improved uniformity in the heating process when combined with other technologies.
  • More control in the heating process than conventional thermic processes.
  • Zero waste processing, avoiding the heating medium for transmission.
  • Improved safety: more healthy food due low level and more effective processing.
  • Important synergies with other technologies taking advantage from the radiation heating that this technology implies.


Disadvantages

  • The potential selective heating absorption is limited by the water absorption range that overlaps the one of many organic materials.
  • Expensive technology due to the electricity cost compared with direct thermal heating.
  • Potential loss of color and quality deterioration, proper control is critical.
  • Complex size and shapes of food product may limit the technology application.

(Pan, Atugulo & Li, 2014)


Base

  • Infrared radiation is electromagnetic radiation from 0.7 to 1000 micrometers of length. The base of its behavior can be predicted by the Stefan-Boltzmann law, Plank Law, Wein´s Law relating the heat/energy and temperature.
  • The infrared radiation do not depend on an absorption medium and it is converted to heat directly in the material. IR provides efficient heat transferring the energy without contact between the heat source and the material.
  • Gases in general absorb very little infrared radiation.
  • Main absorption groups are hydroxyl group found in water and carbohydrates; Aliphatic carbon in carbon-hydrogen bond, found in fats and proteins; the carbonyl group found in fats and proteins; nitrogen hydrogen found in proteins, carbon double bound found in unsaturated fats. Absorbing from lower to higher wave length. The strongest absorption bands are close to the absorption peaks of water (overlapping problem of heating).
  • There are several factors that affect the absorption process: Water content (as less water, better heating), thickness (as less thickness, more heating) and physicochemical nature of the product.
  • The wave lengths matching the bands of the water/ food product may allow a tailored and more effective heating process.

(Pan, Atugulo & Li, 2014)


Description of techniques

  • Carbon twin emitters allow both short and long wave emits within the IR range, leading to a flexible intensity of heating. Short wave (1300-1600 K and 300kW/m2, metal industry), medium wave (90 kW/m2, drying and curing products) and long wave emitter (up to 40 kW/m2, stream of hot air due to water vapor). There are also electric and gas fired emitters that produce CO2 and Vapor Water. The design of irradiation chamber is critical and reflective internal surfaces are required for an efficient process.

(Pan, Atugulo & Li, 2014)


Changes in process (Operation Unit Applications)

Cooking

  • IR technology enables rapid cooking processing times with an enhanced product quality and a reduction in energy consumption.
  • Important synergies with microwaves and hot air technologies.
  • Relevant roosting applications tasted for coffee already.
  • Lower initial investment cost compared with electrical cooking.
  • Three periods can be identified in the process: the first one is about Increasing surface temperature up to 100°C with minimal weight loss; then an evaporation zone forms as the transfer of moisture goes from the central parts of the foods to the exterior; the duration of the final stages may be about 20% of the total time, the central temperature of the product increases reaching about 98°C.


(Pan, Atugulo & Li, 2014)


Pasteurization

  • Effective method for decontaminating food while conserving high product quality.
  • Reduced energy consumption. It has a higher heating capacity and a shorter response time compared with conventional thermal methods.
  • Processing factors: IR intensity, temperature of the food, peak wave length and bandwidth of the IR heating source, type of microorganism, physiological phase of microorganism and the size and type of food materials.
  • Tested on Milk sterilization (E. Coli inactivation), fruit surface decontamination, almond pasteurization (Salmonella, heating to 100°C and holding at 90° C for 10 min. achieving 5.5 log reductions) and rice disinfection (replacing chemical method of using Methyl Bromide; de-infest freshly harvested (60°C) and stored raise (including Beatles 60°C, 1-20 min.) ; moisture removal preserving quality.
  • Similar to UV technology with potential to damage DNA, RNA, ribosomes, cell envelopes in microbial cells.

(Pan, Atugulo & Li, 2014)


Cases:

Infrared surface pasteurization of Turkey frankfurters

Innovative Food Science & Emerging Technologies, Volume 5, Issue 3, September 2004, Pages 345-351

Lihan Huang


Blanching

  • The blanching process can be accelerated with IR technology. It is possible a continuous blanching operation using infrared technologies with constant heat radiation enabling simultaneous enzyme deactivation and moisture removal. Intermittent heating (constant product temperature during the process). The specific parameters for the application are the residual enzyme activity, the moisture removal and the degradation limit of the product. The internal texture, vitamins and minerals of food with minimal damage.

(Pan, Atugulo & Li, 2014)


Drying

  • Infrared drying enables a rapid processing, especially in food with high content of moisture. Matching the infrared wave lengths with the band of the water enables a high efficient process. A heating medium for transmission is not requiring, saving on material use and producing less waste.
  • Typical combined application with hot air drying, sequential with freeze drying and with vacuum drying.
  • The infrared technology has the following standard components: Drying chambers, IR heaters, vacuum pump and a control system.
  • Using infrared technology in combination with freezing drying leads to high quality, crisper dried products of lower dehydration ratio in shorter time with improved energy efficacy.
  • The technology work best in thin-flat materials

(Pan, Atugulo & Li, 2014)


Cases:

Effect of carbonic maceration on infrared drying kinetics and raisin qualities of Red Globe (Vitis vinifera L.): A new pre-treatment technology before drying Innovative Food Science & Emerging Technologies, Volume 26, December 2014, Pages 462-468

Yuxin Wang, Hongyan Tao, Junsi Yang, Kejing An, Shenghua Ding, Dandan Zhao, Zhengfu Wang

Infrared drying of apple slices

Innovative Food Science & Emerging Technologies, Volume 5, Issue 3, September 2004, Pages 353-360

Dorota Nowak, Piotr P. Lewicki


Peeling

The technology enables fast heating and low penetration, heating only a shallow layer while leaving intact the edible inner part with minimum change in texture. IR dry peeling produce high quality peeling products without using water or chemicals. There are also lower peeling loss, thinner peel thickness while achieving the same degree of peelability and ease of peeling. Rapid and uniform surface heating is critical. Consideration of the size and shape of the product are required. Better color and texture in the product can be achieved.

  • Enables to have peel as a value added by product.
  • Used in Peaches and tomatoes.

(Pan, Atugulo & Li, 2014)


Cases:

Peeling of tomatoes using novel infrared radiation heating technology

Innovative Food Science & Emerging Technologies, Volume 21, January 2014, Pages 123-130

Xuan Li, Zhongli Pan, Griffiths G. Atungulu, Xia Zheng, Delilah Wood, Michael Delwiche, Tara H. McHugh


Energy Savings

  • Compared with conventional thermal processing, IF enables a more efficient use of energy due to the better control potential and the capacity for tailoring the heating depending on the food.
  • Savings due to avoid material use (the conventional heating medium for example).


Change in Energy Distribution

This system use electricity instead of the conventional direct thermal energy. Increasing the electricity demand of the site and lowering the quantity and quality of thermal energy required.


References

  • Kaine-Krolak, M., Novak, M (1995) 'An Introduction to Infrared Technology: Applications in the Home, Classroom, Workplace, and Beyond ...', Closing the Gap, Presentation Manuscript, (University of Wisconsin, Madison), pp. 1 [Online]. Available at: http://trace.wisc.edu/docs/ir_intro/ir_intro.htm (Accessed: 27th March 2015).
  • Pan, Z., Atugulo, G., Li, X. (2014) 'Part IV: Alternative thermal processing: Chapter 25 infrared heating', in Sun, D. (ed.)Emerging Tehcnologies for Food Processing. UK: Academic Press, pp. 361-377.



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