Deformability of soft plant cells accessed by 3D images

Deformability of soft plant cells accessed by 3D images. Leverrier C. et al. 2017 (Accepted for publication in Food Biophysics).

Abstract
Purees of fruit and vegetables are concentrated suspensions of plant particles. To make the link between process and texture, it is necessary to understand their rheological behaviour which is related to the plant cell volume fraction. However, plant particle’s volume fraction is not clearly defined yet. From a physical point of view, plant cells can be considered as soft, deformable and compressible particles, which are susceptible to decrease their volume under stress or when the concentration increases, making the volume fraction difficult to determine. To our knowledge, the ability of cells to compress themselves has never been shown directly from processed fruit or vegetable. Using confocal microscopy and 3D reconstruction, we developed a protocol to determine the volume of cells in concentrated suspensions. Four suspensions varying in cell wall content were analysed. Cells’ volume only decreases in highly concentrated suspensions. We demonstrate by direct observation the ability of plant particles to compress and decrease their volume when the concentration of the suspension increases.

Design of model apple cells suspensions: Rheological properties and impact of the continuous phase.

Design of model apple cells suspensions: Rheological properties and impact of the continuous phase. Leverrier C. et al. (Accepted for publication in Food Biophysics).

Abstract
The objective of this work is twofold: to develop a relevant model system to study plant cells suspensions’ rheology and to evaluate the impact of the continuous phase composition and viscosity on the rheological behaviour of apple cells suspensions. Model suspensions of individual or clustered apple cells were developed. Rheological behaviours of both type of suspensions were observed separately, suspending from 0.145 g/100mL to 3.48 g/100mL of particles in
the model media and in the original apple serum. Our results show that model suspensions successfully reproduce the rheological behaviour of apple purees, following three concentration domains. In particular, cell clusters greatly reproduce the behaviour of bimodal apple purees, suggesting that clusters dominate the rheological behaviour of the whole puree. One of our main result is that continuous phase does not affect elastic properties of suspensions in the concentrated domain since they are essentially governed by particle interactions: G’ values are similar whatever the continuous phase. If the continuous phase has the main impact on diluted suspensions’ viscosity, its effect becomes smaller as particle concentration increases. A lubricating effect was observed in the concentrated domain for continuous phases containing polymers. Presence of polymers may help in structuring the network in the intermediate domain.