Automated Sweet Potato Starch Processing Technology Principle

Fully Automated Sweet Potato Starch Processing Production Line: Production Process: Conveying – Cleaning – Crushing – Screening – Sand Removal – Sedimentation (or Concentration) – Dehydration – Drying – Air Cooling and Packaging.

Automated Sweet Potato Starch Processing Technology Principle:

I. Basic Principle of Cleaning

The purpose of cleaning is mainly to remove the mud and sand adhering to the outer skin of the sweet potatoes and to wash away the outer skin of the sweet potato tubers. Cleaning the raw materials for starch production—fresh sweet potatoes or dried sweet potato slices—is the foundation of starch quality; the cleaner the cleaning, the better the starch quality.

II. Basic Principle of Crushing

The purpose of crushing: Sweet potato starch is mainly stored in the fleshy part of the tuber, with only a small amount stored in the inner skin. The purpose of crushing is to break down the tissue structure of the sweet potato, allowing the tiny starch granules to be easily separated from the tuber. Starch released from the cells is called free starch; starch remaining in the cells inside the residue is called bound starch.

Crushing is a crucial step in fresh sweet potato processing, directly impacting the starch yield and quality. The requirements for crushing are:

1. To break down the cells of the fresh sweet potato as much as possible, releasing more free starch granules;

2. To facilitate separation. Excessively fine pulp is undesirable, as it hinders the separation of starch from other components and increases the difficulty of separating fine residue.

III. Basic Principles of Screening

Sweet potato residue consists of long, thin fibers, larger in volume and with a higher expansion coefficient than starch granules, yet lighter in specific gravity. Using water as a medium, the crushed pulp is further filtered to remove the starch slurry.

IV. Basic Principles of Purification and Sedimentation

Mud and sand have a higher specific gravity than water and starch granules. Based on the principle of gravity separation, cyclone desanding or sedimentation in a flow channel can achieve satisfactory results. The specific gravity of starch slurry is close to that of water, but lighter than that of starch granules. Its shape is palmate, and the longer the processing cycle, the greater its adhesive properties, causing it to stick to the screen and starch granules, making separation difficult. Therefore, fresh raw materials, a short process flow, and timely separation are required.

V. Basic Principles of Dehydration

The concentrated starch slurry still contains a significant amount of water, requiring further dehydration before drying.

VI. Basic Principles of Drying

Currently, starch factories generally use airflow drying (also called rapid drying). The entire process is completed in an instant, so the internal moisture of the starch granules is dried before it can gelatinize, thus preventing gelatinization or degradation.

Airflow drying is a co-current drying process, that is, a co-current process of wet powder material and hot airflow, consisting of heat transfer and mass transfer processes. When wet starch comes into contact with hot air, the hot air transfers heat to the surface of the wet starch, and then from the surface to the interior—this is the heat transfer process. Simultaneously, moisture in the wet starch diffuses from the interior of the material in liquid or gaseous form to the starch surface, and then diffuses from the starch surface through an air film into the hot air—this is the mass transfer process. The process involves a high-temperature airflow evenly exchanging heat with the wet starch within the drying tube, causing the dried starch to become powdery. After cooling, it can be packaged and stored.