Effect of salts on the properties of aqueous sugar systems, in relation to biomaterial stabilization. 1. Sorption behavior and ice crystallization/melting

M.F. MAZZOBRE; M.P. LONGINOTTI; H.R. CORTI; M.P. BUERA

CRYOBIOLOGY

Elsevier

Lugar: Amsterdam; Año: 2001 vol. 43 p. 199 - 210

0011-2240

Trehalose and sucrose, two sugars that are involved in the protection of living organisms against extreme conditions, and their mixtures with salts, were employed to prepare supercooled or freeze-dried glassy systems. The objective of the present work was to explore the effects of different salts on water sorption, glass transition temperature (Tg) and formation and melting of ice in aqueous sugar systems. In the sugar-salt mixtures, water adsorption was higher than expected on the basis of the water uptake by each pure component. In systems with a reduced mass fraction of water (w £ 0.4), salts delayed water crystallization, probably due to ion-water interactions. In systems where w > 0.6, water crystallization could be explained by the known colligative properties of the solutes. The glass transition temperature of the maximally concentrated matrix (Tg´) was decreased by the presence of salts. However, the actual Tg values of the systems were not modified. Thus, the effect of salts on sorption behaviour and formation of ice may reflect dynamic water-salt-sugar interactions which take place at a molecular level and are related to the charge/mass ratio of the cation present without affecting supramolecular or macroscopic properties.