Залежність стану води від температури в зернах кефіру при різній гідратації

• Datum: 2016
• Hauptverfasser: Gun'ko, V. M., Turov, V. V., Krupska, T. V., Golovan, A. P., Pakhlov, E. M., Tsapko, M. D., Skubiszewska-Zięba, J., Charmas, B.
• Format: Artikel
• Sprache: Englisch
• Veröffentlicht: Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2016
• Schlagworte: кефірні гранули; слабоасоційована та сильноасоційована вода
• Online Zugang: https://www.cpts.com.ua/index.php/cpts/article/view/369
• Назва журналу: Chemistry, Physics and Technology of Surface

Kefir grains (KG) were studied using low-temperature 1H NMR spectroscopy, DSC, and thermogravimetry to analyse the influence of the hydration degree on the properties of water bound in KG, as well as effects of dispersion media (air, weakly polar CDCl3, CDCl3 + F3CCOOD) and temperature. An increase in water content added to dried KG results in changes in water structure and supramolecular organisation in bacteria, low- and high-molecular components of KG. Five types of water are observed in KG: (i) weakly associated water characterised by a low value of the chemical shift of proton resonance dH = 1–2 ppm; (ii) strongly associated water at dH  = 4–5.5 ppm (similar to that of bulk water), (iii) weakly bound water frozen at 265 K < T < 273 K; (iv) strongly bound water frozen at 200 K < T < 265 K; and (v) bulk water, which does not directly interact with bacteria, cells, and macromolecules. NMR cryoporometry and thermoporometry based on both DSC and thermogravimetry give close results and show detailed changes in intracellular and extracellular organisations of water and other low-molecular weight compounds due to hydration/dehydration, addition of weakly polar (CDCl3) or strongly polar (F3CCOOD) compounds, heating or freezing.