Influence of particle network characteristics on the dynamic rheological properties of red lentil puree fractions

The complex cellular structure of vegetables purees has a great impact on their rheological properties, as affected by particle-related factors such as their shape, size and concentration. The aim of this study was to unravel the impact of particles characteristics on viscoelastic properties of fractions from a red lentil puree containing high contents of starch and protein. Four particle fractions were separated from the puree: cell fragments (CF), single cells (SC), cell clusters (CC), and a mix of all particles (MP). Their composition, structural properties, stability upon dilution and dynamic rheological properties after reconstitution at three pulp contents were investigated. CF was mostly made of aggregated cell fragments containing extracellular starch, SC was characterized by dispersed parenchyma cells filled with intracellular starch, and CC of cell clusters containing some intracellular starch too. The viscoelastic properties seemed driven by starch location, as SC and CC had higher power law constant values (K') and flow stress (σf), with lower yield strain (γy) than CF: extracellular starch could form a continuous entangled network entrapping particles and decreasing the gel strength. CF was also the most stable to dilution, which emphasized the role of extracellular starch on networks cohesion. K' and σf were higher in CC than in SC, probably because of the roughness of cell clusters assessed by their low solidity values, as opposed with single cells of smoother surface. Such work on pulse puree particle networks helped understanding the mechanisms involved in a complex structured food system rich in starch and protein.