Structural properties of pectin-gelatin gels. Part II: effect of sucrose/glucose syrup

Small deformation dynamic oscillation and bright field microscopy were used to examine the structural properties of single and mixed high methoxy pectin and gelatin systems in the presence of sucrose/glucose syrup blends. Go-solute concentrated (greater than or equal to 78%) systems of the polysaccharide form rubbery structures which are readily transformed into glassy consistencies according to the time-temperature superposition principle. Increasing amounts of co-solute in the gelatin samples induce changes in viscoelasticity from that of conventional hydrogels to mechanical traces that cover much of the plateau region and the beginning of the glass transition area. Furthermore, manipulation of the protein/sugar ratio can result in strong crystalline matrices, or viscoelastic solutions where the co-solute forms the continuous phase and the gelatin inclusions can undertake a conformational transition. The properties of the single components were used to rationalise the phase behaviour of their mixtures. Upon triggering the gelation of pectin, mixtures call be made where either gelatin or both components form a continuous phase. Results are discussed in the light of evidence obtained from the ethylene glycol work in Part I. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.