Solid Drinks Processing Methods

Freeze drying, fluidized bed granulation and spray drying are the three main processing methods in the production of solid beverages. Freeze drying is an advanced drying process, can better retain the nutritional and flavor components of the material, but the investment is high, the application is limited; fluidized bed granulation is suitable for drying low juice or juice-free materials; spray drying technology is suitable for drying liquid materials with high juice content, due to the low temperature of the material heated, the time is short, and the material can be better retained nutrients and flavor components. Other processing methods for solid beverages include spray freeze drying and vacuum drying.

1、Freeze-drying method
Freeze-drying method is to freeze the water in the material into solid ice, under vacuum conditions, so that the water directly sublimation into water vapor escapes, so that the water is removed from the material. Characterized by nutrients and volatile components are well preserved, but the processing cost is very high, so the production of solid beverages with freeze-drying method is still very little, only a small number of higher value-added products such as instant tea powder, coffee powder application.

2、Fluidized bed granulation
Granulation technology has a wet granulation, dry granulation, rapid mixing granulation technology and fluidized bed granulation and other four kinds. Fluidized bed granulation, also known as boiling granulation, is the conventional wet granulation of mixing, granulation, drying and other three steps in the closed container at a time to complete the new granulation technology, can greatly reduce the amount of auxiliary materials, made of particles of uniform size, good results.

The growth of particles in fluidized bed granulation generally has three mechanisms – attachment, coating and cumulative granulation. Fluidized bed granulation process is often these 3 roles together to make particles grow.

The purpose of granulation in the food industry, the main solution to the instant solubility, and make excellent appearance, improve mobility, easy to package, thereby increasing the value of goods.

At present, the domestic production of instant fruit and vegetable solid drinks, generally using the method of blending, granulation, drying, the use of swing granulator for granulation, but the main disadvantage of the direct use of swing granulators to process solid beverages is the high content of its auxiliary materials.

3、Spray drying
Spray drying is the use of atomizers will be dispersed into fine droplets, and in the hot drying medium quickly evaporate the solvent to form a dry powder process, the form of material can be a solution, suspension, emulsion and other pumps can be transported in the form of liquids, drying products can be powdered, granular or agglomerated particles.
Spray drying of solid beverages in a wide range of production, in addition to widely used in the production of milk powder, instant soybean powder and tomato powder, there are lychee powder, lotus root powder, banana powder, strawberry powder and so on have also been reported.

The powder processed by spray drying has a small loss of nutrients, good color, in addition to direct brewing, can also be used as ingredients. However, the spray-dried powder, generally smaller particle size, poor mixing, need to be granulated before you can directly mix. Instant milk powder is the most typical kind of solid beverage that is rapidly dissolved in hot and cold water through spray drying and then agglomerated and granulated, and its research is also the most popular.

Research progress of instant solubility of solid beverages

1. Definition of instant solubility of solid beverages
Solid beverages are required to have good color, flavor and stability during the brewing process, in addition, the speed of its dissolution process also directly determines its quality.

Broadly speaking, instant solubility includes two meanings, the first is a solid beverage that can be quickly and completely dissolved in water, such as instant tea, orange crystals, fruit treasures, etc., which can be completely dissolved in water; the other refers to the formation of uniformly dispersed suspension after rapid dispersal, such as soymilk powder, milk powder and so on.

2, solid beverage brewing process
Powder brewing process is divided into four steps: wetting, sinking, dispersion, and finally dissolution of fast-soluble powder in the capillary force under the penetration of water, a few seconds to complete the process of dissolution, but if the material surface has a hydrophobic group, the powder is difficult to wet, the general use of binders, such as maltodextrin, and surfactants, such as lecithin granulation (eg, powdered milk) to improve the fast-soluble.

3、Theoretical study of solid beverage brewability
Solid beverage dissolution process is essentially a mass transfer process, water from the main body of the aqueous phase to the particle surface, and then diffuse into the interior of the particles, from the internal and external surfaces of the particles at the dissolution of particles, dissolved particles into the aqueous phase and diffuse from the interior of the particles to the outside surface of the particles, and then from the outside surface of the particles by diffusion or convection to the main body of the aqueous phase, until the particles are completely dissolved.

According to the molecular mass transfer theory, the factors affecting the mass transfer rate include the internal and external surface area of the particles, the diameter of the particles, the thickness of the liquid film and the concentration difference from the inside of the particles to the surface of the particles, the difference in the concentration of the dissolved particles contained in the main body of the aqueous phase outside the surface of the particles to the liquid film, the diffusion coefficient and so on.

Increase the internal and external surface area of particles, reduce the diameter of small particles and liquid film thickness, improve diffusion or convective mass transfer coefficient are conducive to the dissolution of particles. Generally speaking, the smaller the particle size, the larger the specific surface area of the particles, the faster the dissolution rate; but the particle size is small, the gap between the particles is also small, the surface of the particles are dissolved when they stick together to prevent the water from stretching to the interior of the powder, and the particle size is small, the bulk density is light, floating in the liquid, relatively reducing the wetting area, the dissolution rate is not fast.

Solid beverage powder properties research progress

Powder properties include powder particle fluidity and cohesion, particle size and size distribution, particle shape, apparent density, surface properties, electrostatic charge, moisture content, etc., which directly affects the powder storage, packaging and processing, in which the flow characteristics of the powder in the processing, packaging, such as from the storage tanks and silos between the flow, transportation, mixing, as well as compression and packaging play a large role, so the determination of powder fluidity on the Powder engineering is of great significance.

The industrial processing of powders requires a reliable and consistent flowability so that storage and feed silos neither overflow nor generate dust.

Powder particles exist between the flow of friction, static friction, adhesion and cohesion, etc., of which the adhesion of intermolecular gravity caused by inter-particle gravitational force, also known as van der Waals force; particles with anisotropic electrostatic charge caused by the gravitational force; attached to the capillary force of moisture; particles caused by the surface of the uneven mechanical occlusion, and sometimes these kinds of force exists at the same time.

Representation and measurement of these mechanical properties of flow or static between powders is expressed in terms of the friction angle.Jenike pioneered the use of the shear chamber method to measure the flow properties of powders in 1964, and later on there was the annular shear chamber method, which can measure the internal friction of the powder itself.

Particle shape, surface components, particle size, and water content also have a great influence on the flowability and agglomeration of the powder, the higher the water content, the liquid bridge between the powders increases, the stronger the adhesion, and the worse the flowability, among which the particle size has the greatest influence on the flowability of the powder.

Research progress of fruit and vegetable composite solid beverage

At present, the research on fruit and vegetable composite powder is relatively small, still dominated by single-powder research, production in order to make up for the defects of a certain kind of fruit and vegetable in nutrition, color or flavor, often several kinds of fruits and vegetables are mixed together in the processing of fruit and vegetable solid beverages are no exception. At present, fruit and vegetable composite powder processing research to process-oriented, theoretical research is weak.