High hydrostatic pressure induced physiological changes and physical damages in asparagus spears

Abstract

High hydrostatic pressure (HHP) has been applied as a postharvest treatment in fresh fruits and vegetables for certain purpose, e.g. as a phytosanitary approach to control quarantine insect pests. However, detailed information on HHP-induced physiological changes of plant tissues in a broad range of pressure is limited. In this context, asparagus spears were treated by HHP at mild (10–200MPa) and high pressure (400–600MPa) for 0.5 to 30min. At pressure lower than 200MPa, the CO2 production rate of asparagus spears increased with raising pressure and extending treatment times, while no sign of respiration was found at treatment pressures higher than 400MPa. A shift from aerobic respiration to fermentation was noticed in the sample treated at mild pressure, which might be attributed to the HPP-induced hypoxia stress, enzyme activation, and cell damage. Generally, HHP treatment resulted in a decreasing firmness; however, slight but substantial recovery in firmness was observed in the treatments at pressure higher than 100MPa for 20min, which might be caused by fortification of intercellular adhesion through formation of new ionic linkages in cell wall pectic polysaccharides. Overall, it was suggested that 200MPa could be a threshold for causing instant lethal metabolic disorder and severe physical damage in asparagus spears.