17H-6 |
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S. D. BHALE1, M. Lima1, S. Bhattiprolu1, and W. Prinyawiwatkul2. (1) Dept. of Biological & Agricultural Engineering, Louisiana State Univ. Agricultural Center, 149 E.B. Doran Bldg., Baton Rouge, LA 70803, (2) Dept. of Food Science, Louisiana State Univ. Agricultural Center, 111 Food Science Bldg., Baton Rouge, LA 70803-4200 Thermal processing affects textural and rehydration properties of vegetables. Many consumers prefer processed vegetables with crisp/firm texture. Alternative thermal processing is needed to preserve the quality of processed vegetables. The ohmic heating is a direct electrical-resistance or electro-conductive heating. It is effective for vegetables containing abundant ionic molecules (e.g., salts and acids) that act as electrolytes, making electrical current easily penetrate inside the foods where heat is generated. Our objective was to determine effects of ohmic heating on textural and rehydration properties of carrot. Carrots were cut into cubes (12x12x12 mm) and ohmically heated at 1-Hz or 60-Hz until the center temperature had reached 40C. An electrical field gradient (40 Volts/cm) was maintained during heating. Samples were then rehydrated and stored for 6 days under controlled relative humidity (RH) of 11.2%, 33.7%, 55.7% or 75.3%. Hardness, adhesiveness, cohesiveness, chewiness, and fracturability were determined. The raw untreated sample was used as the control. Two replicate experiments were conducted. Data were statistically analyzed (a=0.05). Hardness, fracturability and adhesiveness of 1-Hz samples stored at 75.3% RH were different (p<0.05) from those at 57.7% RH. At 60-Hz, only hardness of samples at 75.3% RH was different from those at 57.7% RH. Hardness and fracturability of samples heated at both frequencies were different from the control at 57.7% RH. Adhesiveness, cohesiveness and chewiness of 1-Hz samples were different from the control at 57.7% RH. The moisture content of samples during storage was affected by %RH. The moisture content of 60-Hz samples at 11.2% RH was different from those at 33.7%, 55.7 % and 75.3% RH after 6 days of storage. There was a significant correlation between cohesiveness and chewiness and moisture content of 60-Hz rehydrated samples at 32.7% and 75.3% RH. This study demonstrated that ohmic heating significantly affected textural and rehydration properties of carrots.
Session 17H, Food Engineering: Thermal processes
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