Ohmic treatment of solid foods: effect on textural properties.

OLIVERA, D.; SALVADORI, V.; MARRA, F.

Conferencia; EFFOST Conference. New Challenges in Food Preservation: Processing - Safety ? Sustainabil; 2009

Food industry is highly innovative in terms of products, but less so in terms of processes. Consumer demands for high-quality products have motivated researchers and food industry to explore alternative methods as replacement for traditional processing methods. Ohmic heating uses electrical resistance of a material to generate heat. Although ohmic processing of liquids is industrially applied, ohmic heating of solid foods has not yet led to commercial applications and has proven a great challenge(Palaniappan & Sastry, 1991; Marra et al., 2009). Also, the importance of electrically induced damage in plant food material in typical ohmic heating experiments has not been well established yet (Wang & Sastry, 2000; Lebovka et al., 2005). The aim of this work was to verify the effects of ohmic heating treatment on texture of fresh solid food (without brine solutions), subjected to constant electrical field gradient (1100 V/m; 2200 V/m; 3300 V/m). Samples of fresh potatoes, carrots and apples were cut into cylinders (d = 30 mm, h = 0,90 mm) and ohmically heated for 60, 120, 180 and 240 seconds. For temperature monitoring, thermocouples type K were inserted into the samples at the begin and at the end of each treatment. Texture measurements were performed in a universal testing machine Instron 4301, with a 100 N load cell, using a single-cycle compression test. The raw untreated sample was used as control. Ten replicate experiments were conducted. Data was statistically analyzed (á=0.05). Cooking loss for ohmically heated samples for all cooking times was < 5%. Stress?deformation behaviour of plant tissues treated by OH differs appreciably from raw untreated samples for all cooking times. Firmness of solid samples decreased with ohmic heating time. This shows the importance of the electroporation mechanism in plant tissue damage induced by ohmic heating, which is controlled by temperature-induced changes in the cell membrane structure. This study confirmed that ohmic heating significantly affects texture of solid foods, producing structural damage, even though food has a low electrical conductivity.