Date of Award
Master of Science
Food Science and Technology
Melvin R. Johnston
Jimmie L. Collins, James A. Corrick Jr
This study was conducted to determine the effect of high tempera-ture (100°F) storage on quality attributes of catfish fillets prepared to an intermediate moisture level by cooking in a solution containing glycerol, NaCl, K-sorbate and propylene glycol, followed by breading and deep-frying. A preliminary experiment was designed to study the effect of dif-ferent levels of glycerol in the cooking solution on the moisture content and water activity of the cooked samples. Subsequently, breaded fillets were deep-fried to determine the effect of frying time on moisture content and water activity. The samples previously cooked in the glycerol con-taining solution (30 percent and 40 percent) were fried for one, two, three, four and five minutes. Additional samples were prepared for storage and further analyses. Methods for preparation were based upon analyses of samples prepared in preliminary experiments. A cooking solution containing 35 percent glycerol, 5 percent NaCl, 0.5 percent K-sorbate and 1 percent propylene glycol and a frying time of three minutes were selected to produce fillets with a desirable water activity (Aw = 0.80). The product contained 38.9 percent moisture, 21.2 percent glycerol, 4.29 percent salt, 19.2 percent crude fat and exhibited a water activity of 0.80. A relative humidity of 76 percent was necessary to establish the isotherm point. Samples stored at 100°F were analyzed at weekly intervals for five weeks for moisture content, firmness, color, pH, rancidity and iodine value. From this study the following results were found: 1. The moisture content decreased from 38.9 percent to 37.8 percent. 2. The shear values increased from 400 to 475. 3. The breaded fillets retained their light yellow color through-out storage. 4. The pH was lowered from 6.64 to 6.41. 5. The TEA value increased from 0.953 to 1.502. 6. The iodine values increased from 141.1 to 154.4. 7. The samples were contaminated after frying and when the prepared samples were stored at 100°F, the water activity was increased from 0.8 (at 70°-75°F) to near 1.0. In further research of this nature, care must be undertaken to adjust the water activity so that at the higher tempera-ture the activity will be 0.8 to avoid spoilage.
Chen, Chang-Cheng, "Intermediate moisture breaded, deep-fried catfish. " Master's Thesis, University of Tennessee, 1970.