Degumming is a core process in silk powder products production. It removes sericin, the outer coating protein of silk fibers, and is essential for enhancing product performance, stability, and suitability for various end-use applications. The main reasons for degumming include:
Enhancing Core Performance for Intended Applications
Sericin accounts for 20 to 30 percent of silk's total weight and is naturally hard, brittle, rough to touch, and poorly water-absorbent.
For silk powder products, sericin reduces purity and solubility. Degummed silk protein powder products, primarily composed of fibroin protein, dissolve more easily and are readily absorbed by the skin for cosmetic applications or digested by animals for feed applications. This ensures consistent performance across different applications.
Improving Stability and Shelf Life
Sericin contains many hydrophilic groups, making undegummed silk powder prone to moisture absorption, mold growth, bacterial contamination, and clumping during storage. Degumming removes most of the hydrophilic sericin, reducing moisture sensitivity and significantly enhancing storage stability. This is particularly important for long-term warehousing and international shipping.
Reducing Allergenicity and Meeting Safety Standards
Sericin is a foreign protein that may cause skin allergies in sensitive individuals. For cosmetic-grade or medical-grade silk powder products, degumming is mandatory. Removing sericin improves biocompatibility, lowers allergen risk, and helps meet international safety standards such as EU EC 1223/2009 and US FDA requirements.
Increasing Purity and Ensuring Consistency
Clients in cosmetics, nutraceuticals, and feed industries require high protein purity and a stable amino acid composition. Sericin differs from fibroin and may interfere with formulation stability and efficacy. Degumming rate, typically 90 percent or higher, is a key quality indicator, ensuring batch-to-batch consistency in silk powder products for all intended applications.
Common Degumming Methods
Physical degumming: High-temperature boiling or ultrasonic treatment, suitable for feed-grade silk powder products with lower purity requirements.
Enzymatic degumming: Uses proteases to specifically hydrolyze sericin. This method is highly efficient and causes minimal damage to fibroin protein, making it ideal for cosmetic-grade and medical-grade silk powder products.
Chemical degumming: Weak alkali solutions such as sodium carbonate hydrolyze sericin. While cost-effective, this method can damage fibroin structure and is gradually being phased out.