Corn starch production
The process is as shown in the figure below: ①Cleaning. The corn kernels are removed from soil, stones, grass stalks, metal parts and other inclusions through processes such as air selection, screening, magnetic separation, and water washing. A combination screen combined with an air screen is commonly used, with a row of permanent magnets installed at the outlet. The cleaned materials are directly sent to the water tank for cleaning, and then enter the soaking process. ②Soak. It softens the corn kernels and relaxes the combination of starch granules and protein, making it easier to separate. In addition, the lactic acid bacteria in the soaking solution can play a preservative role. Use 0.1-0.3% sulfurous acid solution as the soaking liquid. The general soaking temperature is 48-52°C and the time is 36-56 hours. In general factory-scale production, 8 to 12 soaking barrels with a volume of 7 to 10 tons or more are used to form a soaking system, so that the corn and the soaking liquid are in counter-current contact. The moisture absorbed by the corn finally reaches 45%, and the dry matter is dissolved 6.0~6.5%, the concentration of the soaking solution is about 2%, and the latter is concentrated by vacuum evaporation. ③ Degermination. The soaked corn kernels are first coarsely crushed with a grinder until the germ is separated from the endosperm without being broken. Then the coarsely crushed starch is prepared into a starch milk with a concentration of 7 Be’ in a separation tank, and the germ with a smaller specific gravity is floated out from the starch milk. For example, a hydrocyclone can separate the corn embryos directly. Then wash off the attached starch with water, then use a centrifuge to remove the surface water, and finally dry it with an ebullating bed dryer to obtain relatively pure dry corn embryos. ④Crush. Degerminated corn kernels contain a lot of fiber and need to be further crushed with 1 to 2 impact mills or 3 to 4 grinding wheels to maximize the release of starch and form a more uniform starch milk. ⑤Screening. Crush the obtained starch milk and separate the fibers through 4 to 5 centrifugal sieves of 80 to 130 mesh or 5 to 6 curved sieves with sieve strip gaps of 50 to 75 microns. Then it is sent to the roughing process. The separated fibers are dehydrated by centrifugation and finally dried. ⑥Refined. The screened starch milk contains more protein.