The typical mechanical measurements used in orange factories in order to obtain information related to the quality of the fruit are dehydration and oil-gland break stress. Those measurements are costly and destructive. This paper reports the study of the following magnitudes: oil-gland break stress, dehydration, velocity and absorption coefficient of ultrasound waves in the orange peel in order to find correlations between the measurements related to the ultrasound propagation, that are easy to do automatically, and the typical mechanical measurements. A destructive experimental set-up system has been developed for the assessment of the ultrasonic magnitudes. The measurement procedure and a study of the evolution of the four magnitudes using a sample of 140 oranges "Salustianas', conserved in two different environments are presented. We show that the ultrasound magnitudes change with the dehydration of the fruit peel and the control procedure test can be carried out with ultrasound techniques. (c) 2005 Elsevier Ltd. All rights reserved.