The first step in producing starch with dried potato is to clean it, use screening, air separation, magnetic separation equipment to remove impurities, then soak it. There are two soaking methods: one is to crush the dried potatoes before soaking them, the other is to soak the whole piece of dried potatoes in a container.

0.02mol/L saturated Limewater shall be added into the potato drying soaking water to make the soaking solution ph about 10, soaking time 12 hours, temperature 35-40 ° C. After soaking, the sweet potato contains about 60% water, then rinsed with water, dried potatoes are processed to remove pigments dust. The processing process of soaked potato chips is the same as that of fresh potatoes.

The purpose of soaking potato dry in Limewater is to make the fiber in potato chips expand, which is easy to separate starch after crushing; Make the pigment in potato chips easy to seep out, improve the whiteness of starch; Calcium can reduce the viscosity of pectin substances, making potato paste easy to sieve; Keep alkaline inhibit microbial activity; Starch is easy to precipitate, easy to separate protein, improves recovery rate.

Sweet potato starch often requires acid alkali treatment during refining. Alkali treatment method for processing dried potatoes: Slowly add a 1 ° Be dilute alkali solution to the starch milk to a pH of 12. Stir with a stirrer at a speed of 60r/min for 30 minutes, then let it settle discharge the upper waste liquid. Inject clean water twice to make the starch slurry close to neutral.

The purpose of alkaline treatment is to remove alkaline protein pectin impurities starch. In the process of alkali treatment, 35 ° Be Sodium hypochlorite can be added, the amount shall exceed 0.4% of the weight of dry starch, which can play the role of whitening anti-corrosion.