Making starch from sweet potatoes is a simple and practical technology that is easy to learn and promote. It offers numerous benefits, including convenient raw material sourcing, on-site processing, broad application possibilities, and significant economic returns. This method not only helps in utilizing agricultural by-products effectively but also contributes to sustainable development.
The process of extracting starch from sweet potatoes relies on the physical properties of the components. Sweet potatoes contain water, starch, protein, fat, fiber, and ash. Starch, which is insoluble in cold water and has a higher specific gravity than water, can be separated through mechanical and gravitational methods.
The key steps in the process are as follows:
First, select clean and healthy sweet potato pieces free from pests and impurities. Remove fibrous roots and wash the pieces thoroughly with clean water. Next, chop the sweet potatoes into small 2 cm pieces and grind them into a smooth paste. The finer the grinding, the better the starch extraction.
After grinding, the mixture is filtered using a 60-mesh sieve, followed by a second filtration through a 120-mesh screen. This ensures that only the starch-rich liquid passes through, while the fibrous residue can be used as animal feed.
Once filtered, the starch suspension is transferred to a sedimentation tank, where it is left to settle for 8–10 hours at a temperature between 15°C and 20°C. Higher temperatures may reduce settling time. After settling, the supernatant (a brown liquid) is carefully removed, and the starch is washed two or three times to remove impurities.
Next, fermentation is initiated. A certain amount of water is added to the remaining brown liquid, and the mixture is kept at 15–20°C for about 24 hours. Fermentation is complete when a sour smell develops, the surface turns blue-green, and some foam forms.
After fermentation, the upper layer (referred to as acid slurry) can be reused for the next batch, improving efficiency. The starch is then carefully removed, ensuring that any settled sediment at the bottom is also cleaned.
Finally, the extracted starch is drained and dried to a moisture content of around 14%. Once dried, it is sieved and crushed to ensure a fine, uniform texture. The finished product is ready for use in various applications, such as food, industrial, or pharmaceutical purposes.
This method not only maximizes the value of sweet potatoes but also provides an eco-friendly and cost-effective way to produce high-quality starch.
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