what is dry

Drying usually refers to the process of heating heat on wet materials and removing volatile moisture to obtain solid products with a certain humidity content . During thermal drying, the following two processes occur successively, and the drying rate is controlled successively.

Process 1 : Energy is transferred from the surrounding environment to the surface of the material, causing the moisture on the surface of the material to evaporate, and the liquid is discharged from the surface of the material in the form of steam. The process rate depends on conditions such as temperature, air humidity, air velocity, heat transfer area and pressure of the material . Also known as constant rate drying process •

Process 2: The internal moisture is transferred to the surface of the material, and then surface evaporation occurs. The migration of moisture inside the material . This process is also called the deceleration drying process •

state of moisture

Under certain temperature and moisture content conditions, the surface of the material has a certain water vapor pressure P1 , and its size varies with temperature and moisture content.

The moisture content of the material is high, and the water vapor pressure on its surface is relatively high . If the surface vapor pressure P1 of the material is greater than the water vapor pressure P2 in the air (P1>P2) , the material will be dehydrated and dried . This process is called analytical drying ; such as MPKP2 , then the material will absorb water vapor from the surrounding air and absorb moisture, which is called adsorption . When the water vapor pressure on the surface of the material is equal to the water vapor pressure of the surrounding air, that is, P1 = P2 , the moisture content in the material will no longer change, and there will be Dynamic equilibrium state, this moisture content is called equilibrium moisture . The material moisture exceeding the equilibrium moisture is called free moisture, which can be removed .

 

Based on the above drying principles, the design and production of RIM high-temperature heat pump drying systems generally follow the following principles:

1. The stability and reliability of the drying system must be ensured. To ensure that the quality of the drying material is not damaged during the drying process ;

2. According to the actual needs of customers, tailor-made product systems ;

3. Ensure the green, environmental protection and energy saving of the drying process;

4. Use different drying equipment and methods in a limited combination in order to achieve the best drying quality and drying efficiency ;

5. Ensure the versatility of the equipment as much as possible, one machine with multiple functions, improve the efficiency of equipment use, and reduce investment costs .

Main Nutrients of Fruits /Vegetables

Moisture - the main substance, to be dried to less than 12% Carbohydrate - the drying process must ensure the retention of carbohydrates Organic acid - an important substance that determines the flavor and maturity Nitrogenous substances - will make the material in the drying process Browning occurs Tannin substances—astringent feeling; drying process causes material to change color Sugar first substances—important substances that determine flavor Pigment substances—important substances that determine color— Aromatic substances—Sterilization. It is beneficial to store and dry volatile vitamins - generally very stable. Part of the drying process is easy to oxidize oils and fats - the content is small. Volatile minerals in part of the drying process-low /stable content

Plant antibiotics are contained in some varieties. Important substances for flavor and quality changes

Pretreatment of fruits /vegetables before drying

1. Selection and washing of raw materials to remove mildew , serious pests and diseases. Wash with clean water at room temperature. It can also be soaked in clean water and accompanied by manual turning. Ensure that the sorting and cleaning process does not damage or damage the raw materials

  2. Peeling , core removal and cutting of raw materials

3. The blanching treatment of the raw materials (finishing) --Put the fruit and vegetable raw materials in hot water or steam for short-term heating treatment, and then cool them down immediately. Blanching can destroy the oxidase system of fruits and vegetables , prevent browning caused by enzyme oxidation and further oxidation of vitamins. Hot blanching can also solidify the protoplasm in the cell, lose water and separate from the cell wall, increase the permeability of the cell membrane, facilitate the evaporation of water in the tissue, and speed up the drying speed.

4. Hot water or steam is generally used for blanching, and the time is generally short . Control it within 2-8 minutes.

Important Issues During Fruit /Vegetable Drying

1. Loss of vitamin A and vitamin C —vitamin A ( carotene ) is easily oxidized . Vitamin C is easily oxidized when heated.

2. Changes in color—color is one of the important signs of quality acceptance of drying materials . It is important to maintain the natural color of the material during drying. If not handled properly, it is prone to undesirable color changes such as yellow, brown, or black. When necessary, it is necessary to increase the greening process in the front stage of drying.

3. Loss of aromatic substances—aromatic substances are easily volatile and lost . The loss of aromatic substances is related to temperature, humidity and oxidation. Generally speaking, drying is easy to retain aromatic substances. The retention of aromatic substances largely determines the flavor of the material.

4. Tissue change—hot air convection drying has the most damage to the tissue of the material. Especially in the drying process of high temperature drying and rapid dehydration, the dehydration of the material is uneven and the tissue damage is large.

The function of the dryer is more than that, there are also paper tubes, fireworks, wood, tea, seafood, nuts,,,,, and so on. If you want to know more about the dryer, please go to the homepage Product Center >Heat Pump High Temperature Dryer< Learn more Thank you