ARS | Publication request: MECHANICAL PROPERTIES OF A FRIED CRUST

Submitted to: Journal of Texture Studies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2001
Publication Date: N/A

Interpretive Summary: In the current decade, an ever-increasing proportion of the potato crop goes to processing outlets. Considerable interest is being focused on texture and on the processes that contribute significant textural changes during frying. In order to better understand the frying dynamics in terms of the textural changes taking place during frying, two independent tests were selected to study the mechanical properties of the crust layer of a starch-based material: a puncture test and a three-point bend test. Effects of frying time and frying temperature on the mechanical properties of the fried crust were also analyzed. During these tests, crust samples experienced tension, compression and shearing forces. Maximum force values were reached right before sample failure and both puncture force and flexural force of the crust increased with frying time and temperature, possibly due to strengthening factors such as decreased moisture and increased structural strength upon continuous frying. These tests can be extended to other fried foods and they were found to be extremely valuable and practical in determining textural quality of fried foods. The snack food industry can benefit from these tests since, for these foods, texture plays a very important role in consumer acceptance and the perceived quality of the food.

Technical Abstract: Empirical testing approaches were used to develop general procedures for measuring the texture of a fried crust. A restructured potato model system was fried in canola oil for 5, 10, or 15 min at 170, 280, or 190 degrees C and tested in a Dynamic Mechanical Analyzer. Selected mechanical properties were measured using puncture and three-point bending cells. Forces involved in puncture were a combination of tension, compression, and shear, while the three-point bend test studied the crust flexural properties. Crust deformability seemed to be governed by internal structural yielding. Maximum force at rupture increased significantly with both frying time and temperature. Failure criteria identified and standardized types of failure observed during bending tests.