الملخص الإنجليزي
The structural properties of mixtures with pectin, oxidised starch and glucose syrup were investigated using small deformation dynamic oscillation. The composition of the mixture, pH and temperature course of analysis were designed to imitate the development of confectionery products. In the absence of added calcium, preparations of low methoxy pectin with glucose syrup form viscous solutions, which remain crystal-free at subzero temperatures. Samples of oxidised starch and glucose syrup, on the other hand, exhibit solid-like behaviour due to the crystalline nature of the amylose-like helices. Mixtures of the two polyssacharides with the co-solute show clearly the phase inversion from liquid to solid-like behaviour with increasing amounts of starch in the formulation. The transformation is reflected in the textural properties of samples which vary from thick solutions to firm gels. The viscoelasticity of the system can be modified further by the introduction of high methoxy pectin. Thus preparations of high methoxy pectin and glucose syrup form rubbery gels whose amorphous nature undergoes a glass transition during cooling. The energetic requirement for the formation of the biological rubber was in good agreement with corresponding data in the literature.
