July 17, 2025
Two Weeks in the Fridge: How Kefir and Yogurt Change During Storage
A preprint tracks changes in bioactive compounds in kefir, fermented baked milk, and yogurt over two weeks at 4 °C.
A preprint from a Russian research group describes how the composition of fermented dairy products changes during refrigerated storage.
Study design
The researchers examined 15 cow’s-milk products: yogurt, fermented baked milk, kefir made with commercial cultures, and kefir made with kefir grains. Milk served as the control. Samples were analyzed on days 7 and 14 of storage at 4 °C. Peptides were assessed using UPLC-MS/MS and other fractions using GC-MS.
What the analysis showed
The products contained 348 peptides, 37 amino acids, 25 fatty acids, and 23 mono- and disaccharides. During storage, fermented products accumulated functional peptides, branched-chain amino acids (BCAAs), orotic acid, D-phenyllactate, 5-phenylvaleric acid, and myo-inositol.
Authors’ conclusion
A product’s profile depends on its processing method, raw material, and starter culture. Storage time may also change its functional composition.
Source: Kovalenko E., Sheludchenko M., Shoshina O., Odintsova V., Koshechkin S., Volokh O. bioRxiv preprint, 2025.
