Phase transitions of bovine hide gelatin plasticized by water

It is well known that physical-chemical properties of gelatin are strongly dependent of its origin. The aim of this work is to study the thermal phase transitions of a particular gelatin sample plasticized by water, on the hy groscopic domain. Samples of a bovine hide gelatin were equilibrated, by ad sorption or desorption, under various water activities (Aw = 0.11 0.84) at 25 degrees C, for the DSC study in a DSC TA 2010 equipped with a TA4000 con troller, at 5 degrees C/min. Before first and second scans, the DSC cell wa s quench cooled, with liquid N-2. The first DSC scans obtained with the sam ple, conditioned by absorption in low Aw displayed a well visible baseline shift, followed by a large endothermic peak. In high Aw, another endothermi c peak appears (after glass transition and before the other peak), that bec omes more important as moisture content increases. In the case of samples c onditioned by desorption, this phenomenon was observed in all domain of Aw. In the second scan, only Tg was visible, shifted left All Tg values plotte d versus moisture content (X) displayed a practical glass transition curve and only values of second Tm displayed a monotonic curve versus moisture co ntent.