Zhu Wenxue: Advanced Drying Technology Promotes the Development of Food Industry
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He was the object of cultivating cross-century academic and technological leaders in Henan Province. He won the first National Outstanding Doctoral Dissertation Award in 1999 and served as Dean of School of Food and Biological Engineering of Henan University of Science and Technology for more than ten years. He has presided over the construction of specialty specialty food in Henan Province. "Science and Engineering" built a state-level "Food Processing and Safety" experimental teaching demonstration center.
In this issue of the Food Institute Weekly, Professor Zhu Wenxue, Director of Science and Technology Department of Henan University of Science and Technology, was invited to talk about the person on the cover of the dialogue. He talked about his practice and thinking about using drying technology to upgrade the level of agricultural products and food processing in China and promote industrial development.
General drying technology has its own advantages and optimization combination is the direction of development Professor Zhu Wen introduced in an interview that most agricultural products such as food, fruits and vegetables, etc. due to its high moisture content, perishable deterioration, the need for circulation in the form of dry products. An important role of the drying technology is to reduce the moisture of the material through drying, create a low moisture environment that is not conducive to the growth of the fungus, increase the stability of the material storage, and extend its service life. In addition, it is easier to pack, transport, process and utilize dried agricultural products and foods. By rationally organizing the drying conditions, the process can be simplified, the quality of agricultural products can be improved, food losses can be reduced, and farmers' income can be increased.
Zhu Wenxue said that the current drying technologies for agricultural products and foods mainly include hot air drying, heat pump drying, solar drying, microwave drying, vacuum drying, microwave vacuum drying, vacuum freeze drying and new combined drying technologies. Different drying technologies have different Director. For example, traditional hot air drying is currently the most widely used drying method for grain, fruits and vegetables. Although the hot air drying has a short time and low energy consumption, the dried products are easy to surface harden and the dry product quality is poor. In addition, a large number of heat-sensitive functional components in the material have a lot of losses in hot air drying.
Heat pump drying is the use of a refrigeration system that allows the drying medium to cool and dehumidify, and at the same time recovers the latent heat of moisture condensation to heat the air and perform closed circuit circulation to achieve the effect of drying the material. The dry products produced by heat pump drying technology are of good quality and low energy consumption, but in the middle and late stages of drying, the drying rate is slowed down and the energy consumption is higher, so that the drying time is increased and the product quality is reduced.
The principle of microwave drying is to rely on high-frequency electromagnetic waves to initiate the movement of polar molecules such as water in dry materials, and to rotate and oscillate synchronously according to the microwave frequency. The microwave has the advantages of fast heating speed, short drying time, good selectivity, high energy utilization rate and easy control. Microwave heating can be combined with convection or vacuum drying technology to make full use of the advantages of microwave drying technology, such as rapid and efficient, to reduce energy consumption. Vacuum drying, also known as vacuum drying, is an environmentally friendly green drying technique due to the low oxygen content under low pressure drying conditions, which prevents oxidation and deterioration of the material, avoids oxidation of fat, and produces browning.
Zhu Wen believes that there are different bottlenecks in the application of conventional single-mode drying technology and equipment. The trend in the field of agricultural products and food drying is to study low-carbon energy-saving technologies and optimize combined drying technologies and equipment to reduce energy consumption and improve Drying efficiency and quality of agricultural products and foods. Such as vacuum microwave combined drying technology, combines the advantages of both microwave heating and vacuum drying, is a very promising drying technology.
The anaerobic heat pump drying effectively improves the quality of Chinese herbal medicines Drying theory and technology research Leading Zhu Wenxue said that in the existing agricultural products and food drying methods, in addition to freeze drying and vacuum drying, other drying methods will cause poor oxidation of the material composition in the heating process Change the problem. However, the vacuum drying and freeze-drying equipment are complicated, the drying cost is high, and the use limitation is large. Heat pump drying is a drying method that utilizes a heat pump for dehumidification and heating in a drying medium. The drying temperature is moderate, and it is suitable for the drying of ingredients such as agricultural products and food. Heat pump drying has a relatively low energy consumption and is the preferred method for mass drying.
During heat pump drying, Zhu Wenxue and his research team proposed the use of nitrogen, carbon dioxide, and other inert gases as the drying medium for the heat pump, eliminating contact between the dried material and oxygen, and avoiding deterioration of oxidation and quality during the drying process. Low-temperature, low-oxygen, high-quality drying is achieved.
The research team has done a lot of experiments and explorations on anaerobic heat pump drying, and on this basis developed a dual-evaporator and dual-condenser internal circulation low oxygen heat pump drying equipment. The device retains the low energy consumption characteristics of heat pump drying, while using nitrogen or carbon dioxide instead of air media to achieve a low oxygen drying environment, thereby significantly inhibiting the oxidation reaction during the drying process and effectively improving product quality. Research on the air-dried drying of apples, carrots, kiwifruit and other fruits and vegetables, as well as Chinese herbal medicines such as honeysuckle, rehmannia, salvia miltiorrhiza, lily, etc., showed that when the oxygen concentration was reduced to 1% - 5%, the oxidative degradation of the active ingredient in the material was effectively suppressed. A study has provided important support for the development of the deep processing industry of agricultural products.
Henan Province is an important source of Chinese herbal medicines and has obvious advantages in resources. Over the past 20 years, Zhu Wenxue and his research team have carried out research on modern drying theory and technology of Chinese herbal medicines. The process of changing the functional components of Chinese herbs such as Chinese yam, Eucommia ulmoides, honeysuckle, Salvia miltiorrhiza, Rhizoma dioscoreae, and Hawthorn in the process of drying was studied. The mechanism of degradation of drying quality was discussed, a model of quality degradation was established, and volatile components were proposed. The recovery theory, carried out the study of the discoloration mechanism in the drying process. In the aspect of vacuum drying of Chinese medicinal materials, the relationship between heat and mass transfer of Chinese herbal medicines under vacuum and the relationship between drying rate and content of active ingredients and process parameters were comprehensively grasped. A vacuum drying model for Chinese herbs was established; The continuous vacuum drying equipment has optimized the system and structure of the drying equipment, and is in the leading position in the field of drying Chinese herbal medicine at home and abroad.
Give full play to the characteristics and advantages of disciplines to serve local economic and social development Zhu Wenxue introduced that after more than 30 years of development, the College of Food and Biological Engineering of Henan University of Science and Technology has a theory and technology for drying specialty agricultural products, natural product components and functional foods, food analysis and intelligent detection. , food biotechnology and other directions, the formation of a distinctive characteristic of the subject professional, and applied in the production practice.
For example, in the research on drying theory and technology of agricultural products, a large-scale continuous grain drying equipment was developed and successfully applied to grain drying in the main grain-producing areas. For the first time, finite element analysis was used to simulate the electric field distribution of the microwave freeze-dried resonator, and the development of the heat pump dehumidification and anaerobic hot air drying technology; the theory and structural design of atmospheric freeze-drying based on vortex tube refrigeration filled the domestic gap.
In the research of natural product components and functional foods, the research focused on the separation, purification, functional evaluation and industrialization of functional components such as peony and licorice, and the identification of peony pigment structure and physicochemical properties of Henan Province The second prize for the Progress Award; the development of green industrialization and separation preparation technologies for active ingredients such as glycyrrhizic acid, leading the international level of technology, and the market share of the main products exceeding 70%; the annual output value of the company reached 400 million yuan. In addition, in the field of food analysis and intelligent detection research, the jointly developed lean meat high-sensitivity immunochromatography and digital immunochromatographic test strips have the highest market share in the industry. In the field of excavation and utilization of food microbes, high-vigor yeasts and acetic acid bacteria were targeted and screened, which solved the key technologies for the fermentation of new fruit wines and fruit vinegars such as Chinese yam, wild kiwifruit and hawthorn.
As a leader in food science and engineering science at Henan University of Science and Technology, Zhu Wenxue said that the College of Food and Biological Engineering will continue to combine the advantages of Henan Province's geographical resources and the characteristics of this discipline, carry out scientific research and technological innovation services, and become a regional technological innovation center and technology promotion. center. Strengthen the combination of production, study and research, continuously innovate and develop new technologies and equipment for food processing, help enterprises develop new products, improve traditional processing technologies, conduct scientific research for the main battlefield of social and economic construction, and promote the rapid development of agricultural products processing and food industry.
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