High hydrostatic pressure treatment effects on selected tissue properties of fresh horticultural products

High hydrostatic pressure (HHP) treatments affect the integrity and function of biomembranes and proteins of fresh produces. Initially, pressure affects membrane permeability, directly linked to a reversible decline in cell turgor. Reversibility reflects the restoration of intracellular solute gradients by re-established membrane semi-permeability and functionality of membrane-bound proteins. Above a certain threshold, pressure effects become irreversible resulting in tissue damage. Combining cell pressure probe and tissue impedance measurements allows differentiation between reversible and irreversible effects. Thus, these parameters were comparatively investigated in both fresh red cabbage leaves and in radish tubers, species-specifically exposed to various pre-determined relevant HHP conditions (red cabbage: 150–200 MPa at 35–55 °C for 5–20 min; radish: 100–200 MPa, at 20–40 °C for 5–10 min). These specific treatments facilitated the evaluation of the transition between reversible changes in membrane and protein properties and irreversible damages. While turgor declined immediately after HHP treatments, tissue damage occurred only delayed. The two products differed in their responses to various HHP conditions. Generally, HHP effects were limited and reversible at (and certainly also below) 100 MPa but were amplified with intensity of pressure treatments.