A Novel Method for the Quantitative Detection of Sericin Content in Silk Fiber Based on the Ratio of Aspartate to Alanine

The development of a method for the quantitative determination of the sericin content ratio (SCR) is urgently needed for silk refining and the purification of silk fibroin for biomedical applications. In this work, a series of sericin/fibroin mixed samples with known SCRs were prepared by mixing initial samples of extracted sericin and fibroin from Bombyx mori silk. Significant differences were found in the contents of characteristic hydrophilic amino acids abundant in sericin and hydrophobic amino acids abundant in fibroin, and several linear relationships of SCR associated with the content ratios of Ser/Ala, Asp/Ala, Lys/Ala, Asp/Gly and Ser/Gly were established by amino acid analysis. Subsequently, the linear equation expressing SCR (%) as a function of the Asp to Ala content ratio X (%) was established as SCR = 2.5634X − 12.5587 (R2= 0.9972). The results indicated that the SCR of degummed silks calculated by the equation is more objective and effective than the results obtained by the traditional weight loss method. Our study provides a novel approach for the sensitive and quantitative detection of the sericin content within the detection limit in unknown silks, which can contribute to quality control in the silk production process.