Confocal laser scanning microscopy and image analysis of kinetically trapped phase-separated gelatin/maltodextrin gels

The effect of phase separation on the gelatin/maltodextrin systems has been studied using confocal laser scanning microscopy and image analysis. Stere ological image analysis has been used to analyse the effect of different co oling rates, holding limes, holding temperatures and gelatin types on the m icrostructure at pH 5.3. The quantified microstructural parameters were the volume-weighted mean volume, the interfacial area and the area fraction. A factorial experimental design was used, with cooling rate (0.2 degrees C/m in, 1 degrees C/min, 10 degrees C/min), holding time (0 min, 10 min, 20 min ), holding temperature (20 degrees C, 25 degrees C, 30 degrees C), and two different gelatin types (LH, PS) as design parameters. Gelatin lime hide (L H) has an isoelectric point of pH 4.7, and gelatin pig skin (PS), has an is oelectric point of pH 9.1. The composition was kept constant at 4% gelatin and 5% maltodextrin. The results showed that the phase-separated system was gelatin continuous. The size of the maltodextrin inclusions decreases with increasing cooling rate and was largest at the lowest cooling rate (0.2 de grees C/min). Gelatin PS has larger maltodextrin inclusions and a smaller i nterfacial area than gelatin LH. The size of the maltodextrin inclusions va ried in diameter between 3 and 10 mu m for gelatin LH and between 3 and 18 mu m for gelatin PS. The size of the maltodextrin inclusions increases with increasing holding time and was largest at 20 min. The interfacial area in creases with increasing cooling rates and was largest at 10 degrees C/min. A region was found where the phase separation and the gel formation compete d with each other in connection with mobility. The residence time in that r egion and how fast the sample proceeds through it, are important for the mo rphology of the resulting microstructure. (C) 1999 Elsevier Science Ltd. Al l rights reserved.