(1) Selection of raw materials: Due to different sweet potato varieties, their quality and starch content are also different, even if the same variety is in different producing areas, its quality is also very different. In order to choose a good variety of processed starch, it is required that sweet potatoes with high starch content and diseases are not only unsuitable for starch processing raw materials, but also spread to other potato pieces during storage, which are easy to rot and cause losses, so it is necessary to remove the diseased potato pieces.
⑵ Water washing: pour fresh potatoes into a vat, add clear water, turn them over manually, take them out after washing, and drain the remaining water.
⑶ Crushing: The drained fresh potatoes are crushed into pieces with a crusher, and the size of the pieces is less than 2 cm to facilitate crushing.
⑷ Grinding and filtration: This is the main link in the production of sweet potato starch, which affects the product quality and starch yield. Sending fresh potato pieces into a stone mill or emery mill, adding water and grinding into mashed potatoes, wherein the ratio of fresh potato weight to water is 1: 3-3.5. Then pour the mashed potatoes into a sieve with a pore size of 60 meshes and filter.
5. Slurry mixing: put the filtered starch milk into a vat, and then add acid pulp and water in proportion to adjust the acidity and concentration of the starch milk. The acidity and concentration of starch milk are closely related to the precipitation of starch and protein. If the content of lactic acid in starch is too large, starch and protein will precipitate at the same time, resulting in unclear separation of starch. If the acid is too small, both protein and starch do not precipitate well, and they are emulsified and cannot be separated. According to the production experience, the optimum ph value of acidic pulp is 3.6-4.0. The concentration of starch milk in the tank is 3.5-4.0 Baume, and the amount of acid slurry is 2% of starch milk. After adding acid pulp, the ph value of starch milk is 5.6. If the temperature is high and the fermentation is fast, the amount of acid slurry can be reduced appropriately.
[6] Skimming and sitting in the cylinder: after mixing the slurry, let it stand for about 20-30 minutes, and then skim the cylinder. Take out the mixed solution of clear swill, protein, fiber and a small amount of starch on the upper layer, leaving the starch on the bottom layer. After skimming, the bottom starch was added with water to make starch milk, which made the starch precipitate again. In the process of precipitation, it plays the role of acid slurry fermentation, which is called sitting in the tank. Control the temperature and time when sitting in the cylinder. The sitting temperature is about 20 degrees Celsius. It must be kept warm in cold weather or hot water can be used when adding water to stir. Tank fermentation must be fully developed and properly stirred in the fermentation process to promote the completion of fermentation. Generally, the sitting time is 24 hours, which can be shortened in hot weather. After fermentation, starch precipitates.
(7) Skimming filtration: The acid pulp produced by sitting in the tank is called bidirectional pulp, which is mainly used in the acid pulp method. The normal fermented sour pulp has a clear aroma and the color of the pulp is as white as milk. If the acid pulp is under-fermented or over-fermented, the color and fragrance are poor, and the effect is not good when it is used for pulp mixing. Skimming is skimming off the acid pulp above for pulping. After skimming the starch, sieve with a 120 mesh fine sieve. The screened material is fine slag, which can be used as feed. The undersize is starch, which is transferred to a small bucket. After the starch is transferred to a small bucket, it is washed with water and left for about 24 hours to prevent fermentation.
Be pulverized: