SIZE AND LOCATION OF ICE CRYSTALS IN PORK FROZEN BY HIGH-PRESSURE-ASSISTED FREEZING AS COMPARED TO CLASSICAL METHODS

In high-pressure-assisted freezing, samples are cooled under pressure (200 MPa) to -20 degrees C without ice formation then pressure is rele ased (0.1 MPa) and the high super-cooling reached (approx. 20 degrees C), promotes uniform and rapid ice nucleation. The size and location o f ice crystals in large meat pieces (Longissimus dorsi pork muscle) as a result of high-pressure-assisted freezing were compared to those ob tained by air-blast and liquid NZ Samples from the surface and centre of the frozen muscle were histologically analysed rising an indirect t echnique (isothermal-freeze fixation). Air-blast and cryogenic fluid f reezing, having thermal gradients, showed non-uniform ice crystal dist ributions. High-pressure-assisted-frozen samples, both at the surface and at the central zones, showed similar, small-sized ice crystals. Th is technique is particularly useful for freezing large pieces of food when uniform ice crystal sizes are required. (C) 1998 Elsevier Science Ltd. All rights reserved.