Superheated Steam Drying

Drying food is one of the oldest methods of preserving food. However, this method of preservation is still very relevant in today’s world. With more and more dried food products coming onto the market, the need for new innovative drying technologies is increasing. The principle of dehydrating foods to inhibit the growth of micro-organisms is the platform on which new methods such as drying using superheated steam are evolving. Superheated steam drying (SSD) is an innovative method of processing food. Its various applications mean that this drying technique has a wide range of possible opportunities and disadvantages. In this report, I will be looking at how this technique is used in the food industry to process food. In particular, I will be

One area that has garnered a lot of interest in relation to SSD is its capacity to decontaminate certain foods such as wheat grains. This review will also strive to investigate the effect of SS drying on the nutritional quality of foodstuffs. SSD as an alternative to hot air drying overcomes some of the problems faced by HAD while also favouring the environment.

The principle of superheated steam drying:

The basis of superheated steam (SS) is that the steam must first be saturated. Saturated steam is formed when the temperature of the water is raised to its boiling point. In order for the saturated steam to become superheated steam it must be heated beyond its boiling point at a correlative pressure. When the steam reaches a temperature above its boiling point, it is then referred to as unsaturated or superheated steam. Condensation occurs in saturated steam when the temperature falls. Unlike saturated steam, condensation does not occur in SS so long as the temperature is kept above saturation temperature. This allows for the temperature of SS to fall a little at times without condensation occurring. One of the main attractions

1 Diagram of superheated steam dryer.

Advantages of superheated steam drying

When compared with drying methods like hot air drying (HAD) SSD has a number of clear advantages. SSD allows for energy savings because evaporated air becomes part of the drying medium, in HAD moisture laden air has to be eliminated and new air must be heated to replace it. The rate of evaporation of water in SSD is higher than in HAD as stated by Ezhil (2004). Later Sehrawat et al., (2016) agreed with this, stating that because air wasn’t present in SSD there is no resistance to the evaporated material diffusing in its own vapour.

The benefits of SSD as drying process are very interesting. Even without comparing it to other methods of drying this drying medium has a lot of potential both for consumers and in industry.

↑ The oxygen free nature of SS processing reduces the risk of explosions and fires. Thus, making manufacturing environments safer. Without oxygen oxidation cannot occur, this is important for foodstuffs like fruit which can lose valuable vitamins due to oxidation.

↑ Using SSD processing technology allows for subsequent processing of the product such as blanching, sterilisation, deodorising and pasteurising (Karimi,