Effect of water activity and temperature on the stability of creatine during storage.
Level 5 - mechanism / opinion, no new human data
In vitro bench chemistry study with no human data
PubMed 19635041 · doi:10.1080/03639040902755197
What was done
The authors evaluated the degradation kinetics of creatine into creatinine in mixtures of glycerol and pH 4.0 buffer solutions across water activity (a_w) values ranging from 0.31 to 0.983 at three storage temperatures (4 °C, 23 °C, and 35 °C). The stability of creatine in crystalline solid form was also assessed.
What was found
Creatine degradation followed first-order kinetics up to approximately the first half-life, after which degradation leveled off. Unlike typical semisolid systems, degradation did not display a dilution effect around an a_w of 0.7. The reaction obeyed Arrhenius temperature dependence, with an activation energy of approximately 20 kcal/mol at a_w ≥ 0.68, increasing to 23 kcal/mol at lower water activities. A semilog plot of degradation half-life versus water activity yielded a linear relationship across temperatures. In crystalline form, creatine showed high stability as long as deliquescence was avoided.
Why it matters
It quantifies how moisture levels and temperature drive creatine degradation to inactive creatinine, establishing physical-chemical boundaries for formulating and storing creatine products.
Limits
The abstract provides no exact numerical half-life values or sample replication numbers. Findings are limited to a pH 4.0 glycerol-buffer model system and cannot be directly generalized to other pH levels, complex matrices, or in vivo conditions. No human or biological testing was performed.
Cited by
- contradicts Creatine does not degrade into creatinine in warm liquid unless superheated for a prolonged period.