Structural parameters that determine the rheological properties of apple puree

The objective of this work is to better understand how the structural parameters (particle content, particle size and serum viscosity) influence the rheological properties of apple purees. An apple puree (called “native”) was ground to obtain dispersions with three different particle size distributions. This mechanical treatment induced the separation of parenchyma irregular cell clusters into regular single cells, modifying both the morphology and the particle size distribution of purees. A separation-reconstitution step made it possible to obtain samples with a wide range of insoluble solids (8-24 g/kg). Pectin was added to some of the samples in order to increase the viscosity of the continuous phase. The rheological behaviour and structural properties of the modified apple purees were investigated using flow and oscillatory rheological measurements, particle size measurements and confocal laser scanning microscopy. Rheological properties such as apparent viscosity, yield stress and elastic modulus decreased as particle size decreased and they increased as insoluble solids content increased. Modelling of rheological properties with master curves made it possible to take into account the apparent relative volume occupied by the particles of different sizes.