Drying in emerging technologies process intensification

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General information

Drying is defined as the application of heat under controlled conditions, to remove the water present in foods by evaporation to yield solid products. It differs from evaporation, which yields concentrated liquid products. The main purpose of drying is to extend the shelf-life of foods by reducing their in-water activity. Micro-organisms which cause food spoilage and decay and many of the enzymes which promote undesired changes in the chemical composition of the food are unable to grow, multiply or function in the absence of sufficient water. Typical applications for drying techniques include dairy products (milk, whey and creamers), coffee, coffee surrogates, tea, flavors, powdered drinks, processed cereal-based foods, potatoes, starch derivatives, sugar beet pulp, fruits, vegetables and spices.

(European Commission 2006)

Further Information: Drying in food industry


Description of technology, techniques and methods

The following technologies are emerging for improving or replacing the conventional drying processes:

Ultrasound

The technology enables lower process temperature and less time. Increase from 30% to 60% on heat transfer between a solid surface and a liquid medium. Freezing drying with ultrasound enables the control the size of the crystals.

(Muredzi, 2012)

Further Information: ultrasound


Pulse Electric Field (PEF)

The technology enhances yield in fruits of about 30 % when exposed to low electric fields. Enhanced mass and heat transfer in one of the most energy intensive unit operations.There are also successful results for Meat and fish (about 30% improvement in mass transfer), reducing the residence time, i.e. red peppers from 360 to 220 minutes. Use about 10 KJ/kg

(Toepfl, Siemer, Heinz, 2014)

Further Information: PEF


Ohmic heating

The technology enables from 24 % to 60% less time with same conventional quality results.The perme abilization of the structure and the redistribution of water are the main reasons for time reductions. Decrease of 20° C in potatoes processing temperature. With Vacuum impregnation synergy it is possible to increase up to 2 times the shelf life.

(Goullieaux & Pain, 2014)

Further Information: Ohmic


High Pressure Processing

The technology enables a high level of quality, especially regarding phenolic levels, antioxidant and vitamin content. There is an innovative process combined with osmotic dehydratation.

(Nuñez-Mancillaa, Pérez-Wona, Uribea, Vega-Gálveza, Di Scalac, 2013)

Further Information: HPP


Microwaves

The technology enables reduce drying time and product degradation. It is suitable for high moisture content products as carrots or mushroom. Microwave hot air in agricultural crops is a promising application. Vacuum impregnation and osmotic dehydration prior to hot air microwave in fruit preservation become widespread for reducing energy consumption, improving the quality and extending the shelf life.

The technology combined with fluidized bed solve the problem of heating homogeneity with even better color quality plus up to 90% drying time reduction. Spouted Bed combination shows good performance at 3.5 W/g and air temperature of 50°C. High initial capital investment is needed, textural damage due to rapid mass transport is possible. Changes in dialect properties with temperature hinder the extensive commercial application.

(Ozkoc, Sumnu & Sahin 2014)

Further Information: microwaves


Infrared

Infrared drying enable a rapid processing, especially 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. The application is typically 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)

Further Information: infrared


Radio frequency

The use of the technology has its major advantage on the generation of heat within the product. Potential targeting the remaining moisture in post baking products as cookies, crakers and pasta.

(Orsat & Raghavan; 2014)

Further Information: radio frequency


Changes in the process

Energy saving potentials

The new technologies enabling energy savings due to a rapid processing. This is possibly by taking advantage of new ways of heat generation allowing a more homogenous heating process. The major potential for energy savings seems to be between conventional thermal drying and electromagnetic technology in any of its applications way.


Changes in the energy distribution system

Drying processes are one of the most energy intense processes. A relevant change in the energy use of this process may be significant for the whole industrial system. The emergent technologies have in common the use of electricity instead of thermal energy. A combination of different technologies may enable a combination of the demand of thermal and electrical energy more suitable for renewable sources of energy.


References

  • Goullieaux A., Pain J.P. (2014) 'Part IV: Alternative thermal processing: Chapter 22 Recent Development in Microwave Heating', in Sun, D. (ed.)Emerging Tehcnologies for Food Processing. UK: Academic Press, pp. 361-377.
  • Muredzi, P. (2012) 'Chapter 5: Ultrasound Processing Technology', in Aleman, M. (ed.) Emerging Non-thermal Food Processing Technologies. USA: CBH books, pp. 167-194.
  • Nuñez-Mancillaa, Y., Pérez-Wona, M., Uribea, E., Vega-Gálveza, A., Di Scalac, K. (2013) 'Osmotic dehydration under high hydrostatic pressure: Effects on antioxidant activity, total phenolics compounds, vitamin C and colour of strawberry 'LWT - Food Science and Technology, 52(July), pp. 151-156.
  • 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.
  • Orsat, V., Raghavan V. (2014) 'Part IV: Alternative thermal processing: Radio Frequency Processing', in Sun, D. (ed.)Emerging Tehcnologies for Food Processing. UK: Academic Press, pp. 385-398.
  • Ozkoc S., Sumnu G., Sahin S. (2014) 'Part IV: Alternative thermal processing: Chapter 20 Recent Development in Microwave Heating', in Sun, D. (ed.)Emerging Tehcnologies for Food Processing. UK: Academic Press, pp. 361-377.
  • Toepfl S., Siemer, C., Heinz V. (2014) ' Part II: Chapeter 8 Pulse Electric Field processing, in Sun, D. (ed.)Emerging Tehcnologies for Food Processing. UK: Academic Press, pp. 147-152.


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