Remote Sensing of Fruit Textural Changes with a Laser Doppler Vibrometer

Abstract

Developmental changes in fruit texture during ripening were determined based on remote sensing of surface vibrations. The technique was evaluated with fruit having a range of firmness and textural characteristics including kiwifruit [Actinidia deliciosa (A. Chev.) Liang et Ferguson, 'Hayward'] treated with ethylene, apple (Malus ×domestica Borkh. 'Ourei')stored at 10 or 20 °C and persimmon (Diospyros kaki L. 'Fuyu') stored at 10 °C. In each case fruit were placed on a stage capable of imparting sine wave vibrations with frequencies ranging from 5 to 2,000 Hz. The vibration transmitted through the fruit to the top surface was precisely measured without any direct contact with the Doppler laser vibrometer. The perceived fruit surface signal was corrected by subtraction of the stage vibration based on an accelerometer signal, hence the true vibrational signal of the fruit mass was determined. The phase shift at selected frequencies was based on the difference between the input and output vibration. The phase shift significantly increased in the range of 1,200 to 1,600 Hz in all three kinds of fruit analyzed as a function of maturation. The resonance frequency, peak height, and peak width of second resonance peak were also determined. The resonance frequency decreased in all fruit as a function of maturation. In apple, the peak height decreased as a function of storage duration, but in kiwifruit and persimmon the peak height fluctuated and a consistent pattern in this particular parameter was not observed. The amplitude of vibration decreased as a function of maturation when the imposed vibration exceeded 1,200 Hz. Data clearly showed that the Doppler laser vibrometer is capable of detecting the phase shift and vibration amplitude of fruit, and can be used as a versatile remote sensory tool for determining fruit firmness and for evaluations of maturity.

Effects of Ripening Stage, Temperature, and Film Wrapping on the Elasticity Index as Determined by a Nondestructive Resonance Vibration Method and Fruit Quality in ‘Irwin’ Mango

“…Relationship between the EI and flesh firmness. Positive correlations between the EI determined by nondestructive resonance vibration and flesh firmness determined by a destructive method have been reported previously in fruits such as pears (Murayama et al, 2006), apples (Motomura et al, 2004), and kiwifruit (Muramatsu et al, 1999;Terasaki et al, 2001). Similarly, we observed a positive correlation between the EI and flesh firmness in mango fruits.…”

“…Conversely, additional research has shown that the nondestructive measurement of fruit resonance is possible using a laser Doppler vibrometer (LDV; Muramatsu et al, 1997Muramatsu et al, , 1999, and LDVs have been applied to investigate the ripening of various fruits such as pears (Murayama et al, 2006), kiwifruit (Muramatsu et al, 1999;Terasaki et al, 2001), apples (Muramatsu et al, 1999), persimmons (Muramatsu et al, 1999), and nectarines (Muramatsu et al, 1996). In addition, Sakurai (2012) developed a smaller, more practical device that could measure the second resonant frequency (SRF) of fruits with accuracy similar to that of an LDV in the field.…”

Prediction of Apple Firmness From Mass Loss and Shrinkage

“…Classical approaches for the nondestructive determination of firmness include fruit responses to imposed vibration, mechanical or sonic impulses, impact force analysis, and ultrasonic testing techniques (Muramatsu et al 1999). These approaches all depend on their correlation with standard destructive measures of firmness such as the Magness-Taylor tester (Magness and Taylor 1925).…”

Estimating the Green's function using a single channel dual-beam interferometer

“…LDVs are optical devices that measure the surface particle velocity of a sample using a reflected laser beam. 18,19 LDVs have been used to characterize the elastic response of fruit, 20,21 rocks, 22 structures, 23,24 and soft tissue phantoms. 25 Typically, LDVs generate a beam of light that has a modulated intensity pattern, I(t).…”