1. Pretreatment of raw coffee beans are selected, that is, the coffee beans should have fresh bean flavor, bright color, complete and uniform particles, few broken beans and impurities, and no mold spots. At the same time, raw beans should be screened cleaning. In order to ensure the quality, vibrating screen and wind pressure can be used. Separation or cleaning by conveying or vacuum conveying.
2. Roasting is the decisive process for the formation of flavor and quality of instant coffee. Rotary drum roasters are generally used. Roasting temperature and roasting time are the key control factors. When the coffee beans reach the required degree of roasting, turn off the heat, stop heating, and spray a certain amount into the oven at the same time. It is good for extraction. The average particle diameter of the ground coffee is about 1.5 mm.
3. Extraction is the complex central part of the process of producing instant coffee. Temperature and pressure are the two direct parameters of the extraction process, and the temperature is the determining factor. If the product is found to have a sour, bitter, astringent taste, etc. The amount of extraction can be reduced from time to time. In turn, the amount of extraction can be appropriately increased to achieve the purpose of ensuring product quality and increasing output.
4. Liquid-solid separation, there will be a lot of solids in the extracted coffee liquid. This requires liquid-solid separation of the coffee liquid before the next step. Generally, a butterfly separator can be used to achieve the required separation effect.
Concentration is generally divided into vacuum concentration, centrifugal concentration, and freezing concentration, vacuum concentration is used here. It reduces the boiling point of water by vacuum, the degree of vacuum reaches -0.08Mpa or more, at this time the boiling point of water is only about 60 degrees. Because the temperature of the concentrated liquid from the evaporation tower is higher than the normal temperature, it must be cooled and then sent to the storage tank to reduce the loss.
5. Spray dryer is the process of forming a coffee powder. The concentrated liquid and aroma liquid are formulated into a coffee liquid mixed liquid, and the coffee liquid is directly sent to the nozzle on the top of the tower through a pressure pump. In the drying tower, the inlet temperature must be controlled between 250-270℃, and the outlet temperature needs to control between 110-130℃. The nozzle and spray pressure are adjusted to make the coffee powder into thick-walled hollow spherical particles, the moisture content is about 3%.
Pay attention to the concentration of coffee liquid in the spray dryer, because the higher the concentration of the solution, the higher the viscosity, and the higher the surface tension, which is conducive to the formation of thick-walled hollow particles, and it can reduce the adjustment range of various operating parameters and temperature and pressure.