Quantitative assessment of phase composition and morphology of two-phase gelatin–pectin gels using fluorescence microscopy

A technique for quantitative determination of the concentrations of polysaccharide and protein in two-phase mixtures by fluorometry has been developed and compared with chemical analysis. In the first case, a general method for fluorescent labeling of carbohydrate polymers was developed. For the latter purpose, two micro-assays were developed on the basis of recent polymer macro-assays. A blend of low-methoxyl pectin and gelatin B was used as a model system. The commercial components were subjected to multi-step purification procedures, and phase separation was initiated by the addition of NaCl to aqueous solutions containing the two polymers. Samples were withdrawn for microscopy after various holding times at 60°C. Tie-lines were determined using both the fluorescent and chemical methods. The results from these methods were in fair agreement with each other and with literature data. A three-phase region was discovered in the pseudo-ternary phase diagram. The morphology of double labeled gels was also studied in two and three dimensions using confocal scanning laser microscopy. The results show promise for the quantitative assessment of phases that contain carbohydrate polymers and in the study of morphological changes that occur during thermo-mechanical processing.