Targeted pectin depletion enhances the potential of high-pressure homogenization to increase the network forming potential of tomato cell wall material

Abstract

The current study addresses the influence of pectin depletion on the potential of high-pressure homogenization (HPH) to increase the network forming potential of the cell wall material (CWM) from tomato. Therefore, the microstructure, water binding capacity and viscoelastic properties of the alcohol-insoluble residue (AIR) and unextractable fractions (UFs) obtained after different levels and methods of pectin extraction were determined in suspension before and after functionalization by HPH. Before HPH, the AIR and the UFs obtained by solvent-based pectin extraction were all characterized by particles displaying cell-like morphology and the storage modulus (G′) of the respective suspensions was maximal at partial pectin depletion. The network forming potential of the CWM could only be increased by HPH when extensive disruption of the cell wall network was realized instead of mainly breakage. Even when higher pressure levels were applied (up to 80 MPa), preceding weakening of the cell wall network by pectin extraction was a prerequisite to favor efficient disruption of the CWM during HPH above deformation and breakage. Apart from the effect of partial pectin depletion as such on the cell wall strength, the impact of the extraction conditions (e.g., acid conditions at high temperature) weakening the residual cell wall seemed important. This had repercussions on the potential of HPH to functionalize the CWM. While the G’ decreased upon HPH (evaluated at 20 MPa) for non-pectin-depleted or partially pectin-depleted CWM generated by using mild extraction conditions, a clear increase was observed upon HPH of CWM which was partially or extensively pectin-depleted using harsher extraction conditions.