I. Decreased starch purity: Increased protein and impurity content
The core function of a hydrocyclone is to separate starch from light impurities such as protein and fine fibers using centrifugal force. When the hydrocyclone tube or underflow outlet is clogged, the internal flow field becomes turbulent, leading to:
Incomplete protein separation: Soluble proteins that should drain from the overflow outlet cannot be effectively separated and mix into the underflow starch slurry, causing the protein content of the finished starch to exceed the standard.
Increased fine fiber residue: Clogging causes insufficient washing, and fine fibers deposit along with the starch, affecting the taste and industrial processing performance.
Experimental data shows that severe clogging can increase the protein content in starch from the ideal 0.35% to over 0.6%, exceeding the food-grade starch standard (≤0.5%).
II. Reduced Starch Whiteness: Grayish or Yellowish Color
Clogging prevents a stable backflow of washing water, making it difficult to remove residual pigments (such as polyphenol oxides from potatoes) and microbial metabolites from the starch granule surface.
Starch milk remains in stagnant areas for extended periods, easily leading to localized fermentation or oxidation, producing colored compounds.
Impurities coat starch granules, reducing light reflection and causing a decrease in whiteness.
This not only affects appearance quality but also limits its application in high-end foods (such as baby food and transparent capsules).
III. Starch Yield Loss: Exacerbated Overflow "Powder Loss"
When a stage hydrocyclone becomes clogged, system pressure imbalance occurs, forcing some starch, which should have drained from the underflow, into the overflow.
Turbid overflow with visible particles: This indicates a significant loss of starch with the waste liquid, directly reducing the extraction rate.
Decreased overall system recovery rate: Under normal operating conditions, starch extraction rates can reach over 95%, but severe clogging can reduce this to below 88%, resulting in significant economic losses.
IV. Obstacles to Subsequent Processes: Increased Difficulty in Dehydration and Drying
Blocking leads to fluctuations in underflow concentration and uneven output starch slurry:
When the concentration is too low, it increases the load on centrifugal dehydration, increasing energy consumption;
When the concentration is too high or contains solids, it easily clogs subsequent screens and pipes, and may even damage the drying equipment.
Furthermore, starch with high impurity content is more prone to gelatinization or caramelization during high-temperature drying, further affecting the quality of the finished product.
V. Increased Risk of Microbial Contamination
Blocked areas easily form "dead zones," where residual slurry rapidly breeds bacteria and mold at room temperature:
Microorganisms decompose starch to produce sugars and acidic substances, altering the pH value and causing spoilage.
The total bacterial count in the finished product exceeds the standard, failing to meet food safety standards and posing a recall risk.
