Modelling the rheology of HM pectin gels filled with different dietary fibers

GENOVESE, DIEGO; FIGUEROA, LILIAN

Hungría

Conferencia; The 3rd International Conference on Rheology and Modeling of Materials; 2017

High methoxyl (HM) pectin gels were added with different types of dietary fiber (apple, bamboo, psyllium and wheat), for later development of fibre-enriched fruit jellies. Control gel was the gel without fiber (other than pectin), prepared by thermal treatment of an aquous solution (pH = 3.5) with 0.5 %w/w pectin and 65 %w/w sucrose. In fibre-added gels, fibre was added to the solution at a concentration of 3 %w/w (in substitution of sugar), which is the miminum amount required for a food product to be declared ?source of fibre?, acording to the Argentine Food Code. These gels may be considered as filler-matrix composite gels, where the pectin gel is the continuous matrix, and fibers (the insoluble fraction) act as filler particles. It is known that when there is good filler-matrix affinity, the filler has a reinforcing effect, increasing the elastic modulus (G?) of the gels. This effect has been modeled by the Kerner-Lewis-Nielsen?s equation, in terms of the volume fraction (), maximum packing fraction (m), Poisson?s ratio (V), and elastic modulus (G?f) of the filler particles. Dynamic oscillatory measurements were performed on the gels to obtain G?. Fibers and control gel densities were measured to obtain  values. It was observed that the experimental increase in G? of the gels due to fibre addition was much higher than the reinforcement predicted by the model. This was attributed to the soluble fraction of the fibers, which might have had a significant effect on the formation and strengthening of the pectin network.