Production of pregelatinized starch by screw extrusionRaw material formula: potato starch.
Production process: starch → starch milk → gelatinization → drying → crushing → packaging
Key points for operation: There are three methods for the production of this starch:
Drum method: there are two kinds of double drum and single drum. The two rollers of the double drum dryer move in opposite directions. The starch lotion is fed between the two rollers heated to about 150 ℃. The lotion is immediately gelatinized, dried to a film shape on its surface, scraped off with a scraper, and crushed to produce the product. Its quality depends on the degree of gelatinization. The product's ability to withstand shear force, aging and viscosity during drying can be adjusted by adjusting the concentration of starch emulsion, roller temperature and speed. The single roller method is to directly deliver the starch emulsion to the roller surface at about 150 ℃ for gelatinization. The single drum type has low thermal efficiency and small production capacity.
Spray method: In a continuous jet cooker, high-pressure steam is mixed with starch milk to make it gelatinize, and then spray is dried quickly to make pre gelatinized starch. The spray drying method is not suitable for high viscosity paste liquid, and the cost of this method is high, which is seldom used.
Extrusion method: This is a method of producing pre gelatinized starch by using a screw extruding and expanding machine according to the principle of extrusion and expansion. Add the wet starch with the water content of 15-20% adjusted in advance into the extruder. The starch is rubbed and extruded by the spiral shaft to produce hot gelatinization. Then, it is extruded by high pressure through small holes with the aperture of 1-10 mm. As soon as the material enters the atmosphere, it will expand and dry instantaneously. After crushing and screening, the pre gelatinized starch is obtained. Due to the high strength of the shear force, the viscosity of the product decreases, and the solubility of the product is greater than that of the product produced by the drum method. Since there is basically no need to add water during the manufacturing process, it can maintain a temperature of 120-160 ℃ with internal friction heat, and no heat source is required for drying, so it is the most economic method recognized for planting