**7. References**

228 Distillation – Advances from Modeling to Applications

Fig. 11. (a) 30 kW belt system for the treatment of tubers or whole fruits, (b) PEF system with

(a) (b)

3 kWh/ton for a complete tissue disintegration. Compared to other cell disruption methods (mechanical: 20-40 kJ/kg; enzymatic: 60-100 kJ/kg; heating, freezing/thawing: >100 kJ/kg) the energy consumption is very low (Toepfl 2006). For tissue softening, where a lower extent of cell disintegration is required, the typical specific energy input for a PEF treatment is in a range of 1 kJ/kg. The same effect can be observed during the sugar extraction process. More than 50 % of the thermal energy can be saved using a PEF treatment (temperature: 40 °C) instead of a thermal treatment (70 °C) in 60 min extraction process with a yield of 80 %

In conclusion the application of PEF offers the possibility to decrease the energy

Food processing is a wide field containing many different process steps and techniques based on the principles of process engineering. The industry is searching for new and innovative techniques to improve the quality of the food and to introduce new products with a simultaneous cost reduction. One of the most promising new novel food processing techniques is the application of pulsed electric fields (PEF). This non-thermal treatment is based on the application of pulses with a certain voltage and short duration times (µs) to the product located between two electrodes. The product is located between the electrodes and is exposed to the electric field. The cells and the microorganisms in the product are affected

For some food processing steps, especially extraction, dehydration and distillation, a rupture of the tissue is required. Many different cell rupturing techniques are available based on mechanical, chemical or thermal treatments, but they often induce a quality loss of the product or the rupture is not sufficient resulting in a low product yield. Using PEF a more efficient rupture of the cells can be achieved. PEF leads to a poration of the cell membrane resulting in a facilitated diffusion out of the cell. The application field has a very wide range such as the extraction yield of juices, oils, sugar and the reduction of drying time

a pipe diameter of 50 mm

(López et al., 2009).

**6. Conclusion** 

consumption and a continuous scale up is possible.

by PEF. Membranes of the cells are destroyed.


Mass Transport Improvement by PEF –

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**11** 

*Turkey* 

**Membrane Distillation:** 

Pelin Onsekizoglu

**Principle, Advances, Limitations** 

*Trakya University Department of Food Engineering, Edirne* 

**and Future Prospects in Food Industry** 

Membrane separation processes have become one of the emerging technologies in the last few decades especially in the separation technology field. They offer a number of advantages over conventional separation methods in a wide variety of applications such as distillation and evaporation. Membrane processes can be easily scaled up due to their compact and modular design; they are able to transfer specific components selectively; they are energy efficient systems operating under moderate temperature conditions ensuring gentle product treatment. Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), pervaporation and electrodialysis are conventional membrane processes that have already gained wide acceptance in food processing (Bazinet et al., 2009; Couto et al., 2011; Gomes et al., 2011; Mello et al., 2010; Quoc et al., 2011; Santana et al., 2011). Membrane distillation (MD) is an emerging thermally driven membrane process in which a hydrophobic microporous membrane separates a heated feed solution and a cooled receiving phase. The temperature difference across the membrane results a water vapour pressure gradient, causing water vapour transfer through the pores from high vapour pressure side to the low one. Some of the key advantages of membrane distillation processes over conventional separation technologies are: relatively lower energy costs as compared to distillation, reverse osmosis, and pervaporation; a considerable rejection of dissolved, non-volatile species; much lower membrane fouling as compared with microfiltration, ultrafiltration, and reverse osmosis; reduced vapour space as compared to conventional distillation; lower operating pressure than pressure-driven membrane processes and lower operating temperature as compared with conventional evaporation (Bazinet et al., 2009; Couto et al., 2011; Gomes et al., 2011; Lawson & Lloyd, 1996b; Mello et al., 2010; Quoc et al., 2011;

Dewatering aqueous solutions is one of the key unit operations encountered in food processing, particularly in the processing of beverages, fruit juice, milk, whey, vegetable extracts, etc. The initial soluble solid contents are increased by concentration process, reducing the volume with consequent reduction of transport, storage and packaging costs. In addition, the concentrates are more resistant to microbial and chemical deterioration as a

**1. Introduction** 

Santana et al., 2011).

result of water activity reduction.

