Dehydrated vegetables are a kind of dried product made by removing most of the water from fresh vegetables after certain processing. Through dehydration, the weight and volume of vegetables are greatly reduced, making them easier to store, transport and sell, and extending the shelf life of vegetables to a certain extent. Although dehydrated vegetables lose a large amount of water during processing, they still retain many of the important nutrients in vegetables. For example, vitamins (such as vitamin C, vitamin B), minerals (such as potassium, calcium, magnesium), dietary fiber and other nutrients in vegetables after dehydration still have a considerable portion of the nutrients to be preserved. Due to the removal of water, the nutrients in dehydrated vegetables are concentrated to some extent. For example, every 100 grams of fresh spinach contains about 30 mg of vitamin C, while the vitamin C content in dehydrated spinach will be relatively higher on a dry weight basis, which makes it possible to obtain more nutrients when consuming small amounts of dehydrated vegetables.
The application fields of dehydrated vegetables will continue to expand, thus driving the market demand for low-temperature belt dryers to grow. Jiangsu Jinwang continuously improves and optimizes the low-temperature belt dryer for dehydrated vegetables. By improving the heating system, ventilation system and material conveying system, the heat is more evenly distributed on the surface of the material, accelerating the speed of evaporation of water and reducing energy consumption at the same time, so as to improve the drying efficiency and the quality of products. The new low-temperature belt dryer uses intelligent control technology to realize real-time monitoring and fine-que control of parameters such as temperature, humidity, wind speed and material thickness in the drying process by equipping advanced sensors, controllers and automation software. This can not only improve production efficiency and product quality stability, but also reduce labor costs and labor intensity, to achieve intelligent production management.
Working Principle of Low Temperature Belt Dryer for Dehydrated Vegetables
(1) Air heating and circulation system
First of all, the air passes through the air filter to filter out the dust and impurities in it to ensure that the air entering the dryer is clean. Then, the air enters into the heater, which can provide heat for the air through steam, electric heating or other heat medium (such as thermal oil). The temperature of the heated air is generally kept in a low range, usually around 40~80° C. This is to avoid high temperatures from damaging the nutrients, color and flavor of the vegetables.
The heated air is transported to the drying chamber by means of a circulating fan, which ensures that the hot air is evenly distributed within the drying chamber and flows at a suitable air velocity. The circulating system enables the hot air to be constantly recycled, which not only improves the energy utilization rate, but also ensures the temperature stability of the drying environment.
(2) Material conveying system
Vegetable materials are evenly spread on the conveying system consisting of conveyor belts. The conveyor belt is usually made of high-temperature and corrosion-resistant materials, such as stainless steel wire mesh or polyester fiber belts, to ensure that no chemical reaction occurs with the vegetables during the long drying process, and to withstand a certain weight and friction.
The conveyor belt moves slowly at a certain speed to transport the vegetables from the inlet to the outlet of the dryer. In this process, the vegetables gradually pass through the various areas of the drying chamber on the conveyor belt, thus ensuring that the vegetables can fully contact with the hot air and realize uniform drying.
(3) Drying process
When the vegetables enter the drying room with the conveyor belt, the hot air exchanges heat and moisture with the surface of the vegetable material by convection. The hot air transfers the heat to the vegetables, so that the moisture inside the vegetables absorbs the heat and turns into water vapor. Due to the low humidity of the hot air, the water vapor will diffuse from the surface of the vegetable material into the hot air.
With the constant movement of the conveyor belt, the vegetables remain in the drying chamber long enough to ensure that most of the water in the vegetables is evaporated. This drying process is a slow and gentle process because low-temperature drying avoids surface hardening, nutrient loss, and color changes due to high temperatures, thus better preserving the original quality of the vegetables.
(4) Humidity control and dehumidification system
During the drying process, the humidity of the air inside the drying room will gradually increase. In order to maintain the efficiency of drying, the dryer is equipped with a humidity control system and a dehumidification system. The humidity sensor will monitor the air humidity in the drying room in real time, and when the humidity reaches a certain threshold, the dehumidification system will be opened automatically.
The dehumidification system discharges part of the air with high humidity out of the drying room, and at the same time, the new heated air will be supplemented to maintain the air humidity inside the drying room in a suitable range to ensure the continuity of the drying process.
(5) Discharge and product collection
After drying, the vegetables arrive at the discharge port of the dryer with the conveyor belt. At this time, the moisture content of the vegetables has been reduced to a level that meets the requirements, and they become finished dehydrated vegetables. The finished products can fall into the collection container directly through the discharge port, or be transported to the next processing stage, such as packaging workshop for packaging treatment through other conveying equipment.
Dehydrated vegetables low temperature belt dryer performance characteristics
(1)High drying quality
Effective retention of nutrients: the use of low-temperature drying, the temperature is usually between 40 ~ 80 ℃, compared with high-temperature drying equipment, can zui greatly reduce the destruction of vitamins (eg, vitamin C, vitamin B), minerals, biologically active ingredients and other nutrients in vegetables. For example, when drying spinach, low temperature can avoid the large loss of vitamin C, so that the spinach after dehydration still retains a high nutritional value.
Maintain good color and flavor: low temperature environment helps to maintain the original color and flavor of vegetables. Because high temperature can easily lead to the browning reaction of vegetables, destroying their color and luster, and at the same time making the volatile flavor substances in vegetables lose. And this dryer can make the dehydrated vegetables keep the natural color and strong vegetable aroma, for example, the dehydrated broccoli can still keep the bright green color, and the taste and flavor are closer to the fresh vegetables.
Good rehydration: Due to the mild drying process, the cell structure of vegetables has not been seriously damaged, so the dehydrated vegetables have good rehydration. When used, they are immersed in water, which can absorb water faster and return to the state close to fresh vegetables, which can play its role better in cooking or processing.
(2)Gentle drying process
Good temperature uniformity: the heated air is evenly distributed in the drying chamber through the circulating fan, which can ensure that the vegetables can receive stable and uniform heat at all positions on the conveyor belt. This uniform temperature field can avoid local overheating or uneven drying, so that the vegetables are in a stable drying environment during the whole drying process, ensuring the consistency of product quality.
Small damage to vegetables: with lower temperature and stable drying conditions, it avoids physical damage caused by high temperature to vegetables such as surface hardening and internal drying cracks. This is especially important for some vegetables with tender texture (such as leafy vegetables), which can ensure that the dehydrated vegetables maintain the complete form and better physical properties.
(3)High efficiency and energy saving
High energy utilization: the air circulation system of the equipment enables the hot air to be recycled, reducing the heat dissipation. When heating the air, only a small amount of heat needs to be supplemented to make up for the heat lost in the process of moisture removal and the heat absorbed by the material, thus effectively improving the utilization rate of energy and reducing the drying cost.
Higher drying efficiency: Although it is low-temperature drying, high drying efficiency can be realized under the premise of ensuring the quality of vegetables through reasonably designed drying chamber structure, conveyor belt speed and air circulation and ventilation parameters. It can reduce the moisture content of vegetables to a suitable level in a relatively short period of time to meet the needs of large-scale production.
(4) Strong operational flexibility
Adjustable parameters: the operator can flexibly adjust the drying temperature, conveyor belt speed, air circulation speed, moisture discharge and other parameters according to the types and characteristics of different vegetables (such as water content, texture, size) and the required zui final water content. For example, for vegetables with high water content, the speed of conveyor belt can be lowered and the amount of moisture discharged can be increased to ensure the drying effect.
Adapt to a variety of vegetable varieties: Whether it is leafy vegetables (such as spinach, lettuce), root vegetables (such as carrots, radishes) or tomato and fruit vegetables (such as tomatoes, chili peppers), etc., all of them can be dried on this equipment. As long as the corresponding parameters are adjusted, good drying effect can be achieved to meet the needs of dehydration of different vegetables.
(4)Strong operation flexibility
Multiple adjustable parameters: the operator can flexibly adjust the drying temperature, conveyor speed, air circulation speed, moisture discharge and many other parameters according to the types, characteristics (such as water content, texture, size) of different vegetables as well as the required zui final water content. For example, for vegetables with high water content, the speed of conveyor belt can be lowered and the amount of moisture discharge can be increased to ensure the drying effect.
Adapt to a variety of vegetable varieties: Whether it is leafy vegetables (such as spinach, lettuce), root vegetables (such as carrots, radishes) or tomato and fruit vegetables (such as tomatoes, chili peppers), etc., all of them can be dried on this equipment. As long as the corresponding parameters are adjusted, good drying effect can be achieved to meet the needs of dehydration of different vegetables.
(5) High degree of automation
Intelligent control system: Equipped with advanced automation control system, it can monitor and control the key parameters in the drying process in real time, such as temperature, humidity, wind speed and so on. Through the data collected by the sensor, the control system can automatically adjust the operation status of the equipment to ensure that the drying process is always in zui state. For example, when the humidity in the drying room exceeds the set value, the system will automatically turn on the dehumidification device.
Reduce manual intervention: automated operation not only improves the production efficiency, but also reduces the error and labor intensity brought by manual operation. The operator only needs to set the parameters on the control panel, and the equipment can run automatically, and it can alarm in time when there is an abnormal situation, which is convenient for the staff to carry out maintenance and processing.
(6) Hygiene and environmental protection
Easy to clean and maintain: the structure of the equipment is reasonably designed, the drying chamber and conveyor belt and other parts are easy to clean, and will not accumulate too much vegetable residue and dirt, in line with the hygienic requirements of food processing. When producing different batches or different kinds of vegetables, it can be easily cleaned and sterilized to prevent cross contamination.
Good environmental performance: due to low temperature drying, the exhaust gas emission generated by high temperature is reduced. And the equipment has low noise during operation, which causes less pollution and disturbance to the environment. Meanwhile, the efficient energy utilization also reduces the environmental pressure caused by energy consumption from the side.
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