Lyophilization

Lyophilization, commonly called freeze-drying, is the process of freezing a peptide solution and then removing the water under vacuum via sublimation. The result is a dry, porous ‘cake’ of peptide that is far more shelf-stable than its solution form — peptides in lyophilized form can typically be stored for years at refrigeration, while reconstituted peptides last weeks.

Almost every research peptide arrives in lyophilized form for this reason. Reconstitution with bacteriostatic water rehydrates the lyophilized cake into an injectable solution; the post-reconstitution stability window depends on the specific peptide but is typically 14–30 days refrigerated.

Visual inspection of the lyophilized cake is one cheap quality signal: a properly lyophilized peptide presents as a uniform white or off-white cake or fluffy powder. Browning, melting, or visible contamination is reason to reject the vial.