Texture and Histological Structure of Carrots Frozen at a Programmed Rate and thawed in an Electrostatic Field

To investigate the most suitable rate of freezing and method for thawing, raw and blanched carrots were frozen with LN 2 (freezing rate: –5°or ‐2°C/min, final temp: ‐30°C) using a program freezer (PF), or were frozen using conventional freezers (F: ‐80°C, ‐30°and ‐20°C). Then, they were thawed in five different ways: electrostatic thawing (ET, ‐3°C, 17 hr); ‐3°C, 17 hr; 5°C, 17 hr; 20°C, 30 min; 100°C, 3 min. Firmness of thawed carrots and amount of undamaged tissues by LM and TEM observations were greatest to least: PF ‐5°C/min < PF‐2°C/ min <‐80°C CF<‐30°CF<‐20°CF, and ET ≧‐3°< 5°< 20°< 100°C, respectively. Results suggest the optimum rate of freezing was ‐5°C/ min. The frozen disks were defrosted comparatively fast even at ‐3°by ET. Drip, cell damage and softening of disks were prevented by ET.