Application of spray drying technology in solid beverages

Spray drying technology has the characteristics of large evaporation area, fast drying speed, low material temperature and easy continuous production. It shows strong superiority in food drying. The spray drying technology and its main process parameters, and the application of spray drying technology in solid beverages are reviewed, which provides some references for further research on solid beverages. Research Status of Spray Drying Technology in Solid Beverage

The study of spray drying technology began in the early 19th century and has a history of more than 100 years in the world. As early as 1865, La Mo nt proposed the use of spray drying to treat eggs. This process of direct atomization and drying into a solid powder in a very short time has made great progress in the 20th century. The spray drying technology started late in China. In the 1950s, a spray dryer was introduced from the former Soviet Union for spray drying of dyes [1??2]. At present, spray drying technology has become more and more mature, and it is widely used in the food industry, such as milk powder [3], whey powder [4], soy milk powder [5], egg powder, juice powder, instant coffee. [6] Production such as. Spray drying technology has the characteristics of large evaporation area, fast drying speed, low material temperature and easy continuous production. It shows strong superiority in food drying. It allows many valuable but difficult to preserve materials to greatly extend the shelf life, making some materials easy to package, store and transport. At the same time, it also simplifies the processing of some materials [7]. In recent years, spray drying technology has been increasingly used in solid beverages, such as strawberry powder, milk powder, pumpkin powder, tomato powder and various plant powder processing.

This paper describes the characteristics of spray drying technology and its application in solid beverages. The determination of technical parameters of spray drying processing is discussed, which provides some references for further research on solid beverages.

1 Spray drying technology and main process parameters

1. 1 spray drying technology

Spray drying is a drying method for processing a solution, an emulsion, a suspension and a slurry into a powder, granule, hollow sphere or agglomerated dry product in a single process [8], mainly using a nebulizer The process of dispersing the liquid into fine droplets and rapidly evaporating the solvent in a hot drying medium to form a dry powder product. Generally, the spray drying stage is liquid atomization! The mist group is mixed with the hot drying medium! The evaporation of the droplets is dry! The dried product is separated from the drying medium. The liquid can be in the form of a liquid which can be transported by a pump such as a solution, a suspension or an emulsion, and the dried product can be powdered, granulated or agglomerated [9]. Compared with the traditional drying method, the spray drying technology has many advantages. It has a fast drying speed and a short time (3~10 s), which is especially suitable for the drying of heat sensitive materials. The drying process is completed instantaneously, and the dried product can be directly obtained from the liquid, avoiding The dust is flying during the drying process; no evaporation, crystallization, solid-liquid mechanical separation, etc.; the product has good dispersibility and solubility, and can greatly retain the color, fragrance, taste and nutrients of the raw material itself; the production process is simple, Easy to operate and control. However, the spray drying method also has some shortcomings that are difficult to overcome, such as high power consumption and low heat transfer coefficient, resulting in low thermal efficiency; the dryer has a large volume, small operation flexibility, and easy sticking phenomenon [10??11].

1. 2 Main process parameters of spray drying technology

In spray drying, the main influencing factors are the homogeneity of the material before spray drying, the inlet and outlet temperature during drying, and the pressure of the feed pump. There are other influencing factors, such as the ratio of sugar to acid of the material, temperature of the feed liquid and feed flow rate, which will have certain influence on the yield and solubility of the product. The ratio of sugar to acid of the material has a great influence on the taste and flavor of the product, and if the softening point of sugar, acid, pectin, etc. is lower than the drying temperature, it will cause serious sticking phenomenon, and some embedding agent needs to be added for embedding. Such as maltodextrin, cyclodextrin, soluble starch, ethyl maltol or carrageenan.

1. 2. 1 The homogeneous parameter homogenization before spray drying is to make the material refinement under the triple action of extrusion, strong impact and pressure loss expansion, so that the materials can be more evenly mixed with each other [ 12 ]. Prior to spray drying, the material is homogenized and has a large effect on the instant drying of the spray to form a uniform fine powder. Then, proper homogenization temperature, homogenization time and pressure are quite important. The general material is 50~60 均 homogeneous for 20min. If the temperature is too high and the time is too long, it may cause damage to the homogeneous equipment. If the temperature is too low and the time is too short, the homogenization effect is not good. For homogeneous equipment, under a certain homogenization temperature and homogenization pressure, the diameter of the fat globules will not decrease significantly after a certain degree of homogenization, and the emulsification effect will not increase much. At the same time, the homogenization time is too long and is not conducive to Increase productivity. When the homogenization pressure is within a certain range, the stability of the homogeneous liquid increases remarkably with the increase of the homogenization pressure. However, when the homogenization pressure reaches a certain value, the stability of the homogenization fluid does not change with the increase of the homogenization pressure [13]. Jiang Changxing et al. [14] In the study of the process parameters of pumpkin powder prepared by spray drying method, the effect is better when the homogenization pressure selected after optimization is 25 MPa. Zhang Yan et al [15] used a homogenization pressure of 40 MPa in the development of health-care bitter gourd solid beverages. Therefore, according to different materials, choose the appropriate homogenization pressure, the general pressure is controlled at 25~50MPa.

1. 2. 2 Inlet and outlet air temperature during spray drying The inlet temperature of dry air undoubtedly affects the energy utilization rate of production, and this factor also affects the quality of the product. Although spray drying is a drying method suitable for heat sensitive materials, temperature is still a factor that must be taken into account for many heat sensitive materials [16]. Moreover, the temperature of the incoming and outgoing air required for different materials to be spray dried is different. Chen Qingxiang et al [16] in the spray drying process research of papaya, the preferred inlet air temperature is 160 ∀; Zhang Yan et al [15] used in the development of health-care bitter gourd solid beverages, the inlet air temperature is 190 ~ 200 ∀ , Exhaust air temperature is 95~ 98 ∀; Wang Jing et al [17] used the inlet air temperature of 135 ∀ and the outlet air temperature of 80 在 in the research of jujube spray drying process. If the inlet air temperature is too high, the material may be coked. If the inlet air temperature is too low, the drying effect may not be achieved. Therefore, you must choose the appropriate inlet air temperature to achieve a better spray effect. According to different materials, the general inlet air temperature is controlled at 140~200 ∀ [9], while the outlet air temperature does not need to be set, but the general outlet temperature should be controlled at 60~90 ∀. 1. 2. 3 Feed pump pressure parameters The pump pressure has a great influence on the spray drying effect. When the pressure of the gas source increases, the discharge speed of the material increases, the amount of compressed air increases, the particle size of the materialized droplets decreases, and the specific surface area increases. After the particles contact with the hot air, the water rapidly evaporates, resulting in serious powder running. The yield is reduced, and the appearance quality such as particle size and fluidity of the product is greatly affected. However, when the gas flow pressure is reduced, the atomized droplet size increases, the specific surface area decreases, the drying speed slows down, and the phenomenon of moisture powder or sticking wall is easily caused, which also affects product quality. Therefore, the appropriate feed pump pressure must be selected. The general pressure should be controlled at 0. 12~ 0. 21MPa [ 13].

2 Spray drying technology in solid beverages. Solid beverages refer to sugar (or no sugar), juice (or no fruit).

Juice, plant extracts and other ingredients are used as raw materials, processed into powdered, granulated or lumped, post-drinked products. A solid beverage is also a granular, scaly or powdered beverage that has a moisture content of less than 3% and has a certain shape and is ready to be consumed after being washed [19]. The production of solid beverages can be carried out by spray drying, vacuum drying, microwave drying and oven drying. However, spray drying plays an important role in the processing of solid beverages due to its unique advantages, especially in powdery solids. The production of beverages.

2. 1 Application of spray drying technology in instant tea beverages

。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。 Zhou Tianshan et al [21] used spray drying parameters in the processing of bitter and cold-soluble instant green tea: inlet temperature 135 ∀, outlet temperature 75 ∀, injection speed 10 mL / min. Tan Hongbin et al [22] pointed out that in the production of instant tea powder, the inlet air temperature is 250 ∀, using a pressure nozzle, the operating pressure is 2. 5~ 3. 0MPa, the bead-like particles can be obtained. Zhou Jianhua [23] The spray conditions used in the development of mulberry instant tea are: feed liquid temperature 45~50 ∀, inlet air temperature 200~220 ∀, exhaust air temperature 80~ 90 ∀, drying chamber temperature maintained at 85 ~ 95 ∀ , the speed is 800~ 1 500 r / min.

2. 2 Application of spray drying technology in the production of fruit and vegetable powder

Li Gongguo [24] used Shantou as raw material to produce steamed bread by blanching, beating, homogenizing and spray drying processes. The spray drying process has an inlet air temperature of 140~180 ∀ and an outlet temperature of 80~100 ∀. The speed is 15 000~ 30 000 r/min. Liu, et al. [25] using pumpkin as raw material, softening, beating, blending, homogenizing and spray drying process to produce pumpkin powder, the spray drying process conditions are inlet temperature 135 ∀, outlet temperature 75 ∀, inlet air volume 0. 9m3 / Min, feed temperature 60 ∀. Huang Hui et al [26] using lychee juice as raw material, maltodextrin, sucrose, sodium carboxymethyl cellulose (CMC), and cyclodextrin as auxiliary materials, using a combination of homogenization and spray drying The lychee solid beverage was homogenized for 15 min at 20 MP, and then sprayed at a wind speed of 125 ∀, an outlet temperature of 80 ∀, a pressure of 80 MPa, and a wind speed of 0.85 m3 / min. Chen Yucai [ 27] using spray

Drying technology produces wild papaya instant solid beverages, which gives a good spray parameter of 173 进 for inlet air and 73 出 for outlet air. Wang Zenan et al [28] in the study of strawberry powder spray drying process parameters and dry-drying agent ingredients, it is concluded that the effect of spray drying is better when the inlet air temperature is 200 ∀, the feed flow rate is 60 mL/min, and the nozzle speed is 25 000 r/min. .

3 Outlook

Spray drying technology is more and more widely used in the production and processing of solid beverages. Because of its own advantages, it not only overcomes the shortcomings of difficult storage of materials, but also preserves the nutritional value of materials, providing better health for people. Guarantee. Moreover, with the improvement of people's living standards and the accelerated pace of life, people are increasingly demanding the color, aroma and taste of food, and the demand for convenient and nutritious food is increasing [29]. High-quality solid beverages are easy to store, easy to eat, adjustable, and nutritious, meeting people's needs. When the spray is dried, the surface temperature of the mist is not high, so the flavor of the food and the vitamins contained therein can be continuously preserved, and it is particularly suitable for heat-sensitive foods. After drying into a powdered product, it is easy to store and transport, and is easy to use [30??31]. Therefore, spray drying is a good method of producing solid beverages. At the same time, spray-freezing technology, food foam spray technology, spray-dried micro-encapsulation, etc., which have been developed on the basis of this, will also take a new step. Spray drying technology will not only be limited to the preparation of solid beverages, but will also gradually expand to the encapsulation of some enzymes, the preparation of special food additives, the production of microencapsulated foods, etc., which has broad development prospects in the food field.