Water vapour adsorption by L-amino acids at different water activities
| Main Authors: | N. Ghosh, D. K. Chattoraj, K. P. Das |
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| Format: | Article |
| Terbitan: |
, 2008
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/5814948 |
Daftar Isi:
- Department of Food Technology & Biochemical Engineering. Jadavpur University, Kolkata-700 032, India E-mail : dkchattoraj@hotmail.com; dkchattoraj@vsnl.net Department of Chemistry, Bose Institute, Kolkata-700 009, India Manuscript received 11 August 2008, accepted 21 October 2008 Experimental studies on the hydration of all 20 L-amino acids by isopiestic vapour pressure method have been carried out in detail. The water vapour adsorption curves of these amino acids resemble type II or type III BET isotherms. The maximum water uptake (Δn01) of the amino acids at relative humidity equal to unity and values of secondary hydration (ns1) of these amino acids at p/p0 equal to 0.92 have been compared critically with each other. Values of Δn01 and ns1 for each amino acid has been found to be different from that of the corresponding amino acid residue obtained from our earlier studies. It appears that many amino acids having hydrophobic side chain may form crystals with strong ionic bonds so that they resist hydration at 0.92 relative humidity. The standard free energies of hydration of all amino acids at p/p0 equal to unity have been evaluated using the Bull equation. The activity coefficients of several amino acids having low solubilities at p/p0 close to unity has been evaluated when hydrated mixtures remain in gel state.