(1) Choose potatoes. Choose sweet potatoes with smooth surface, no pests and diseases, no green heads and moderate size, and leave the small ones.

(2) clean. Put the selected sweet potatoes into the laundry list and put them into the water. Wash away dirt and impurities. Cut off both ends and surface roots.

(3) crushing. The selected sweet potato should be chopped with a pulverizer in time and then ground into pulp. When beating, water should be added while grinding, and the finer the grinding, the better, so that starch particles in cells can be ground out as much as possible and the flour yield can be improved.

(4) filtering. The purpose is to realize the separation of peel residue and starch. Generally, 2-5 feet of hanging cloth is used as the filter bag for filtration, and it is filtered twice. The slurry is thinner for the first time and thicker for the second time. Then the filtrate is sent to the sedimentation tank (skin residue can be used as feed). After staying in Chi Jing for two days, the supernatant in the pool was released. Add clean water with the original water amount of 1/3, stir and filter again. This time, the filtrate enters a small pool and stands for precipitation.

(5) drying the starch. When the water in the pool has no turbidity, that is, after it is completely clarified, the supernatant is drained. Remove the oil powder on the surface of the starch precipitation layer, take out the lower starch, hang it into a powder pile (that is, powder dough), and move it to the threshing floor for exposure. When half of the water in the powder pile evaporates, the powder pile is cut into several parts and exposed to the sun. The threshing floor is located in the leeward and sunny place to prevent dust pollution.

(6) paste. This process is the key to determine the quality of fans. Add 25 grams of alum to every 500 grams of starch, stir 2.5-3 kilograms of cold water, then put it in a large pot and boil it, stirring constantly until the maturity reaches 80-90% (forming gelatinized starch). The batter can be mixed with other starches to form a moderately soft dough.

(7) Conductor leakage and cooling. Prepare two pots (model 8), two cold water tanks and a medium-sized 48-hole colander before silk leakage. Because sweet potato vermicelli is thicker, the hole of colander is slightly larger than other vermicelli. When leaking silk, the paste should be fully stirred evenly, and warm water should be added while stirring. The water temperature is about 50℃, and a mass of powder paste should be grasped by hand to let it spread naturally. If it is not broken, it means that the thickness is moderate and it can start to leak. Prepare a pot of boiling water and keep pouring it into the leaking pot. When the water in the leaky pot is close to boiling (97-98℃), the silk leaks, so that the powder dough will flow down from the hole of the leaky spoon and gradually extend into fine powder strips (if possible, it is best to use a powder machine). After the vermicelli sinks into the bottom of the pot and gelatinizes, it is taken out as soon as it comes out, cooled in a cold water tank, arranged into bundles by hand, placed on a wooden frame, cooled in another cold water tank, and constantly oscillated until the vermicelli is loose into strips, then placed indoors, completely cooled and taken out to dry.

(8) baking silk. Hang the fan in the leeward and sunny place to dry. After drying, it can be arranged and packaged into finished products.

3, the finished product quality requirements

The vermicelli is uniform in thickness, uniform in color, dry and transparent, good in toughness and not easy to break.