VIIIth Symposium organized by AVH Association - Water/sucrose interactionsand the consequences on drying, curing and storage of crystalline sugar -29 March 2001, Maison des Agriculteurs, Reims, France - Abstracts

摘要

Determination of water content of a foodstuff is not sufficient to account for its storability. It is necessary to know on its own the equilibrium relative humidity (ERH) and temperature of storage. Likewise, water/substrate interactions, namely the hydrogen bonding between solvent water and the solute, and in the solvent water itself, are important to know if it is desired to understand the evolution of the system at the molecular level. Considering the stability of crystalline sugar during silo storage and the effect of such parameters as water content, water activity (or ERH) and water structure in the vicinity of the crystals, analysis of these parameters was undertaken with the aim of controlling the caking in bulk crystalline sugar during silo storage. The water content was analyzed using the Karl Fischer titration method. Three fractions of water were determined: surface water, internal water and total water. Water vapor sorption isotherms were established at different temperatures and different crystal sizes. Water structure in the film surrounding the crystals was derived from previous work on water/su- crose interactions using vibrational spectroscopy techniques. Results show that internal water which originates from the inclusion of mother liquor droplets during crystallization does not vary during storage when conditions (temperature, ERH) are varied. Adsorption of water vapor by sugar increases as crystal size decreases the ERH-caking threshold to values as low as 50 percent. Stability of crystalline sugar during storage is interpreted with regard to the molecular interactions occurring in the film of syrup surrounding the crystals.