Common techniques to monitor the quality of fruit at the time of harvest and in storage typically rely on
destructive methods to measure physical properties such as firmness and hydration. The complex, inhomogeneous
composition of most fruit mean that non-destructive ultrasonic methods for quality evaluation
of fruit has typically been unsuccessful. A novel ultrasound method was developed which analyses
the reflections at the transducer-fruit boundary to evaluate the quality of the fruit as a whole. Using a
custom-built ultrasound device, the technique was applied to navel oranges to relate ultrasonic measurements
with physical measurements taken via destructive methods. For a sample of randomly selected
navel oranges, a high level of correlation was found between ultrasonic measurements and the density
of the fruit, allowing the relative water content of oranges to be non-destructively determined regardless
of individual physical characteristics such as size and maturity. When applied to a sample of navel
oranges over a period of nine days, the ultrasonic measurements were found to be highly correlated to
the firmness of the oranges, providing a non-destructive method to replace traditional destructive methods
currently used to monitor orange maturation.