Important Objectives Of Food Drying

1.2 NEED OF DRYING:
Dehydration is an important preservation process which reduces water activity through the decrease of water content, avoiding potential deterioration and contamination during long storage periods. Other important objectives of food dehydration are weight and volume reduction, intended to decrease transportation and storage costs (Celma et al., 2009; Sarimeseli, 2011; Figiel, 2010; Vega et al., 2007; Wang et al., 2007).
Drying is regarded not only as a preservation process, but also as a method of increasing added value of foods. Among food stuffs, particular attention has been given to drying of fruits and vegetables so that diversified products can be obtained to include in breakfast cereals, bakery, confectionery and dairy products, soups, purees and others (Ramos et al., 2003). Drying is a very important industrial operation accounting for 10–25% of the total energy used in the manufacturing process worldwide (Mujumdar and Passos, 2000).
Drying is a process in which water is removed to halt or slow down the growth of spoilage microorganisms and the occurrence of chemical reactions. Dehydration plays an important role in extending the shelf life of fleshy agricultural products. In addition to preservation, drying is used to reduce the cost or difficulty of packaging, handling, storage, and transport by converting raw food into a dry solid. This action reduces the weight and sometimes the volume of a food (Barbosa-Cánovas and Vega-Mercado, 1996).

1.2.1 DRYING OR DEHYDRATION:
Drying is one of the oldest methods of food preservation, and it represents a very important aspect of food processing. The main aim of drying products is to allow longer periods of storage, minimise packaging requirements and reduce shipp...

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...rocess. Therefore, the sensory and nutritive qualities of foodstuffs are effectively maintained as a result of the comparatively short drying time and low drying temperature (Wu et al., 2007).

MICROWAVE DRYING:

Microwave drying is more rapid, more uniform and more highly energy efficient compared to conventional hot air drying and infrared drying (Sarimeseli, 2011; Soysal et al., 2006; Duan et al., 2003; Al-Harahsheh et al., 2009). In a microwave drying system, the microwave energy has an internal heat generative capacity and can easily penetrate the interior layers to directly absorb the moisture in the sample. The quick energy absorption causes rapid evaporation of water, creating an outward flux of rapidly escaping vapour, thus, both thermal gradient and moisture gradient are in the same direction (Dadali et al., 2007; Soysal et al., 2006; Wang et al., 2007).