Sanz et al. (2007) studied the effect of both pre-frying and final frying time on instrumental crispness of French fries and found that an increase in pre-frying time produced an increase in the jaggedness of the force curves, together with an increase in the number of higher amplitude peaks and for the sound signal a significant increase in the number of sound events was found with increasing pre-frying time. Both the increase in the number of high amplitude force events and in the number and magnitude of sound events reflect an increase in crispness.