Sericin Powder — Frequently Asked Questions

Fundamentally, and the two should not be treated as interchangeable silk proteins. Fibroin is the structural filament, dominated by glycine and alanine in a highly ordered crystalline arrangement that makes it strong and insoluble. Sericin is the amorphous gum that binds those filaments together, rich in serine, aspartic acid and threonine, and it is hydrophilic and water-soluble.

Because it was traditionally discharged as waste. Sericin must be removed to produce usable silk yarn, and the degumming effluent carried it into the wastewater, representing both a lost material and a substantial organic load on treatment. Recovering it turns that waste stream into a saleable cosmetic protein and reduces the effluent burden at the same time.

It binds moisture and forms a film. Its polar serine, aspartic acid and threonine side groups give it strong affinity for water, so it acts as a humectant, and it has recognised affinity for skin and hair keratin, so it deposits and remains rather than rinsing straight off. It is used in moisturisers, hair conditioning and masks.

It should be approached with care. Sericin has historically been identified as the more allergenic fraction of silk, and sensitisation reports in textile contexts are generally attributed to it rather than to fibroin. Purified grades are available, and patch testing is appropriate where a product is aimed at sensitive skin.