Lyophilized

A lyophilized product has been freeze-dried: a frozen peptide solution loses its water by sublimation under vacuum rather than by heating, and a dry solid remains in the vial. Nearly all research peptides in injectable-style vials are supplied like this, since hydrolysis of peptide bonds and oxidation of side chains run far faster in water than in a dried state.

Reading the cake

The look of the cake is informative. A solid, even, white cake occupying the expected volume suggests the process was kept under the product’s collapse point. A puck that looks shrunken, glassy or melted points to collapse — typically due to a shelf that was too warm or a vacuum failure — and a lot delivered in that state deserves a closer look at its COA data. Loose fragments, or a cake that has shifted in transit, are normal and only cosmetic.

Why dry material is the benchmark

All storage advice starts from the dry state. Unopened vials cope with long periods in the fridge or freezer and with brief spells at ambient temperature during shipping; after reconstitution, degradation proceeds much faster. Bulking agents like mannitol are sometimes added as excipients to create a visible cake when peptide mass is low, so a 2 mg vial can look surprisingly full.

Related terms

See also cold chain, stability and reconstitution. Our explainer on lyophilization and the storage guide go further; freeze-dried vials are in the shop.