Crispness is one of the most important and desirable textural characteristics that signify freshness and high quality in breaded fried foods. Though many approaches to instrumental measurement of crispness have been made, the best measurements are still inconclusive. There is no reliable method available that can accurately measure and quantify crispness in breaded fried foods.

In this study, the mechanical and ultrasonic techniques were used to determine crispness in breaded fried chicken nuggets under different storage conditions. The mechanical measurements have been made, using an Instron universal testing machine. An ultrasonic non-destructive evaluation system was used to measure ultrasonic properties of breaded friend chicken nuggets. A pair of dry-coupling 250-kHz ultrasonic transducers was used to perform the ultrasonic transmission through the breaded fried chicken nugget. The equipment set up was in the through-transmission mode because breaded fried chicken nugget is highly attenuative material.

A sensory panel of eight members was trained to evaluate crispness in breaded fried foods. Panelists rated crispness on a nine-point category scale (1 = not crisp/soggy, 9 = very crisp). Sensory crispness values for breaded fried foods under different storage conditions were obtained.

Ultrasonic velocity, transmission loss, peak frequencies and its energies, peak force and total energy were determined for each tested product. Correlation between sensory crispness and instrumental parameters suggests that the ultrasonic method can be used to evaluate crispness. The ultrasonic velocity had high correlation with sensory crispness (R2 = 0.83). This indicates that sensory crispness could be reasonably well predicted by the ultrasonic velocity.