Drying or dehydration is one of the oldest ways of preserving agricultural products. It is a process of separating a certain amount of water from fresh fruits, in order to enable its long-term storage in natural conditions without spoilage. With dehydration (reduction of moisture), the activities of microorganisms in the fruit are reduced. Self-produced dry food is just another form of fresh food, without chemical preservatives. One of the advantages of drying vegetables over other canning methods is that dehydrated products can be rehydrated and reused fresh without compromising quality. Dried products are easier to store, pack and transport.
 

Application of renewable energy sources and energy efficiency
Our company aims at greater application of renewable energy sources in agriculture. Several experts in this field were involved in the calculations and design of the dryer. The basic drying parameters are: Temperature, Relative humidity, drying time and air circulation speed for drying.

Digitization
Our company additionally installs in larger dryers Wi-Fi devices for monitoring energy consumption and Wi-Fi data loggers for monitoring relative humidity and temperature. The client from home, through the Android platform can follow the drying process.

Rules for drying vegetables and fruits
The technological process of drying vegetables includes two basic stages: preparation of the drying product and the drying procedure and quality control of the dry product (percentage of moisture in it).
Preparation before drying: Do not crush the fruits. After harvesting, transport should be done as soon as possible to prevent spoilage. Primary fruit processing involves washing, controlling, cutting and sorting. Each culture has a special way of preparation. Dried fruits must:

• To be healthy, fresh and in the stage of technological maturity;

• No foreign smell and taste;

• To be free from impurities from plant protection products above the maximum allowed quantities.

• Handles and seeds must be removed from some fruits before drying

• Fruits intended for drying should never be stacked on top of each other, but next to each other  
  
  Recommended technology for drying certain types of fruit.
  Note: Each manufacturer determines the drying technology depending on the fruit and the requirements of the market or the end buyer. Consult a technologist about this! A very important detail is the way of packaging the dried product.
   

• Plum: The initial drying temperature of 75ºC, and the final from 60 to 65ºC. Drying lasts from 16-18 hours. Dried plums should contain 22 to 26% moisture, which will depend on the method of further processing. Cool the plums before storing.

• Apples Drying temperature should be between 30 and 70º C. Too long drying at low temperature can create mold. Apples should not be dried too fast at high temperatures, because dried fruit will be less tasty. Drying time depends on air temperature and the amount of water apples. Most often, the drying time at a temperature of 50-60ºC is 6 ÷ 8 hours

• Apricot. Preparation: Sulfurization takes place by burning pure sulfur. This should prevent the fruit from darkening. It lasts from 2-3 hours. The required amount is 2.3 kg of sulfur per 1000 kg of fruit. Immersion in sucrose solution can vary from 70-85% Drying temperature of 45-55ºC. Duration 18-24 hours.

• Grapes. White seedless varieties are mostly used for drying grapes, but colored varieties can also be successfully dried. The seedless varieties are Sultanija, Sultanina and the new Belgrade seedless variety. Drying is from 50 to 70 ºC, duration 15 - 17 hours. The grapes are dried to a water content of 10-15%

• Fig. Drying temperature is 45-50ºC, duration 30-40 hours, or 65-75 ºC with drying time about 5 hours (depending on the type of dryer). The water content in the dried fig is 12-22%. Dried figs should be stored at 10ºC in well-ventilated conditions

• Aronia. Drying lasts 66 hours, takes place at a temperature of 45˚C to a moisture content of 10%. The basic aspect of the drying process is related to the amount of water in the fruit.
  
  
  The technology is obtained from the University Goce Delchev Stip. Only a shortened and general version of fruit drying is given above.

Recommended technology for drying certain types of vegetables.
Note: Each manufacturer determines the drying technology depending on the fruit and the requirements of the market or the end buyer. Consult a technologist about this! A very important detail is the way of packaging the dried product.
 

• Tomato: The drying temperature at the beginning is 65-70 ºC, and at the end of the process it should not be above 45 .C. The drying process takes 6-7 hours. The moisture content in the dry product should not exceed 4-5%. After drying, the product is checked, it is done manually in order to remove the pieces that do not match in color, dark or damaged. Due to the hygroscopicity, it should be packed in an airtight container immediately.

• Onion: Drying is carried out with an initial temperature of about 70ºC. The temperature should gradually decrease (drop), so in the final stage it should be around 55ºC. Drying takes 3.5-5.5 hours, and the moisture content of the dry product should be 8%

• Leek. The length of the leek is 30-40 cm, and the diameter 3-5 cm, depending on the variety. The white part of the stem is cut into pieces 5-7 mm thick, the green and white part 6-8 mm, and the leaves into pieces 8-10 mm thick. Drying is at a temperature of 70ºC at the beginning and at the end at about 50ºC.

• Carrots. Preparation: Cut the carrots into circles (thickness 3mm) or cubes (10x10x10mm). The drying air temperature at the beginning of the process is 71ºC for 7 hours and then decreases to 60ºC for the next seven hours. It is dried with initial 95% and final 3.5-4.5% humidity.

• Mushrooms: The temperature in the first four hours should be 43 ºC, and then increase to 75 ºC for 1 hour. During this time the humidity decreases from 87% to 3%. The final product to have good taste and color, dried mushrooms should not be blanched, but immediately after drying are packed in a hermetically sealed package

• Pepper: The initial temperature should not be above 75ºC, and in the later phase 55ºC to 60ºC. The moisture content in the dry product should not be more than 9%, Dried peppers should have a uniform red color and appearance.

Properties that affect the quality of the final dry product are the following:
 

1. Structural properties: Density, porosity, pore size, specific volume

2. Optical properties: Color, appearance

3. Mechanical properties: Resistance to pressure and tension

4. Thermal properties: Glass, crystalline or rubber state of the product

5. Curly properties: Smell, taste and aroma; Nutritional properties: Vitamins, proteins

6. Rehydration properties: Rehydration, rehydration capacity

7. Quality characteristics are related to drying temperature and air flow
   
   The technology is obtained from the University Goce Delchev Stip. Only a shortened and general version of fruit drying is given above.
   
   
   
   .
    

Note: The manufacturer reserves the right to change, without prior notice.

Last revision 14-Mar-22