The most important factor to increase the shelf life of food products in modern technics of food protection is by preventing food spoilage agents including microbial, chemical, biochemical, and physical spoilage. Drying is one method, and various types of dryers have been used in food industries to reduce or eliminate the moisture and increase the shelf life of products including cabinet dryer, tunnel dryer, explosion puffing dryer, foam-mat dryer, fluidized bed dryer, spray dryer, deep bed dryer, kiln dryer, freeze-drying and microwave methods, infrared, electromagnetic waves, electrical resistance, radio waves (high frequency), high pressure, electric pulse, radiation, and ultrasound. Dryer is used in the Food lord brand to prepare the dried vegetables and dried fruits. Moreover, irradiation technic is used by Food lord to reduce the microbial load.
Introducing various types of industrial dryers in the food industry:
Technics to protect food products by dryers are explained as follows:
Cabinet dryer
Cabinet dryer is one of popular dryers to produce dried vegetables and dried fruits. The hot air is circulated on the trays and fruits and vegetables are dehydrated and get dried.
Tunnel dryer
Wagons containing food pass through the tunnel and indirect hot air enters the product without contact with smoke or dust. A tunnel dryer is used for drying all kinds of fruits, vegetables, and medicinal plants.
Explosion puffing dryer
The product is exposed to high temperature and pressure in a short period of time in this dryer, the water in it evaporates quickly, and the product is puffed up and removed by creating an explosion by sublimation. This method has been used successfully for fruits and vegetables. The materials dried by this method have a lot of porosity and it is possible to absorb large amounts of water into these pores.
Foam mat dryer
Foam mat drying is a technic in the food industry to dry fruit juices and vegetable juices. The liquid changes to foam after adding the edible foaming substances that are sustainable by producing the permanent foam. Then, the sustainable foam is distributed on the surface and is dried in atmospheric pressure using hot air (40-90 °C). Methylcellulose, albumen, maltodextrin, and Arabic gum additives are commonly used. Foods can be dried at lower temperatures and shorter time due to the foam porous structure. The porous structure of the dried foam, low drying time, and temperature improve the properties of powder such as color, water absorption rate, and dissolution. Foam mat drying is one of the developing technics in liquid, concentrated, and pureed foods. The advantages of this technic are the high speed of drying, easy reconstruction, and desired properties of the target product.
Fluidized and spray dryers
Fluidized-bed dryer is used for granules. The hot air is blown from the bottom of the bed. The granule is dried after moisture evaporation and exit from another side of bed and the hot air exist from the top of bed.
The spray dryer is proper to produce the powder foodstuffs. For example, it is used to change liquid milk to milk powder. In this way, the spraying liquid foodstuff enters the nozzle from the top of the container. Simultaneously the hot air enters from the side valve. The circulation of the hot air and contact with the liquid removes the moisture of the food. The separated moisture drops to the bottom of the container and the powders are collected. Furthermore, the hot output air, cooled by contacting the cold liquid, exits from the exiting valve at the bottom of the dryer. This dryer has a continuous process.
Deep bed dryer
This technic is used for foods with high resistance against fragility. In this method, the surface layer is dried in contact with the hot source and then heat is transferred to the substrate.
Kiln dryer
This dryer is used for such products whose moisture was taken away by another dryer up to the final moisture of 3%.
Freeze-dyer
The freeze dryer has a container at low pressure and surfaces that transfer the heat inside it. The frozen foodstuffs previously are put on these surfaces. The existed moisture in the food directly changes from solid to vapor, instead of liquefaction (sublimation). The high-quality is preserved because the temperature is low. The freeze-drying process is bath and semi-batch.
Ref: