Effects of low hydrostatic pressure and moderate heat on texture, pectic substances and color of carrot

It was reported that moderate heat (<100°C) with 100 MPa pressure (MHP) treatment for long periods of time (12 h) could kill thermostatic bacterial spores. The aim of this work was to investigate the effect of MHP treatments on the quality of carrots in relation to textural changes, release of pectic substances and color change. Fresh carrot (Duncus carota) tissue was subjected to long periods (3, 6, 9, and 12 h) of moderate heating (75, 80, 85, 90, and 95°C), with or without low hydrostatic pressure. The carrot texture pressurized under 100 MPa was firmer than without pressure treatments at 75-85°C for 3-12 h, whereas there was no significant difference between the treatments at 90 and 95°C for 9-12 h and the firmness was almost same as conventional cooking at 100°C for 40 min. The release of pectic substances was lower in MHP treatment than in the normal heat treatment. There was no significant difference of color in any treatments. These results indicate that the combined treatment of low hydrostatic pressure and moderate heat could be used as an effective alternative to conventional thermal processing for higher food quality from the viewpoints of high sporicidal activity, large pressure vessel construction and low cost.