Rheological properties and microstructure of tomato puree subject to continuous high pressure homogenization

Tomato puree was processed by continuous high-pressure (CHP) homogenization at 69-276 MPa, for 1-3 passes. Laser scattering and light microscopy showed CHP reduced the pulp particles to ∼10-100 μm, producing smaller and more uniform particles, with processing at 276 MPa and 2 passes producing greatest particle reduction. No differences in moisture or color were found due to different treatments. In general, G′ > G″ for all samples, suggesting a soft gel network. Both the storage modulus (G′) and loss modulus (G″) decreased with CHP pressure. G′ decreased modestly with frequency between 0.1 and 2 Hz, and more dramatically between 2 and 30 Hz, with behavior characteristic of entangled polymers. In general, yield stress decreased with homogenization pressure, but increased with number of passes. CHP-treated samples had lower consistency and were less shear-thinning than the control. Repeated passes increased the consistency of CHP samples. The results suggest CHP processing produced smaller and more uniform particles, causing a reduced level of microstructure that contributes to elastic properties at small deformation.