Stable silk protein fragment compositions

A composition comprising silk fibroin protein fragments having an average weight average molecular weight selected from 40 kDa to 45 kDa, from 45 kDa to 50 kDa, or from 50 kDa to 55 kDa, and a polydispersity from about 1.5 to about 3.0, wherein:

• the silk fibroin protein fragments are substantially devoid of sericin;
• the composition is substantially homogeneous;
• the composition includes between 0 ppm to about 500 ppm of inorganic residuals and between 0 ppm to about 500 ppm of organic residuals;
• and the composition does not spontaneously or gradually gelate and does not visibly change in color or turbidity when in a solution for at least 10 days.