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Higashi Hiroshima, Japan

Sakurai N.,Hiroshima University | Terasaki S.,Applied Vibro Acoustics Inc. | Akimoto H.,Hiroshima University
Acta Horticulturae

The resonant frequency of fruit obtained by vibrating the fruit with a range of frequencies (100-3000 Hz) of sinusoidal wave is closely related with the firmness of fruit, which is generally related to its maturity. An apple vibrated by a vibrator showed several resonant peaks. The lowest resonant peak (f1) was found to reflect the local information of the area attached by the vibrator. The second lowest resonant peak involves the vibration of the whole fruit. The vibration mode at 2nd resonant frequency was physically defined as 0S2, one of the spheroidal modes (nSm). An elastic modulus (E) of the fruit can be calculated with the 2nd resonant frequency (f2) as, E=a×f22×ρ(1/3)×m(2/3) (α is a shape constant; ?, fruit density; m, mass of fruit). We defined Elastic Index (EI) as EI= f22×m(2/3), since a is constant, and ρ is nearly unit. Correlation coefficients between kiwifruit firmness measured by a conventional penetrating method and EI were over 0.9 in core, locule interface and outer pericarp. was correlated with the fruit maturity by sensory evaluation. In melon, correlation coefficient between EI and sensory score was 0.96, while that between soluble solid (%) and the sensory score was only 0.26. EI of immature melon predicts days waiting for full maturity and relishing period of melon fruit. Abnormal low f2 distinguished core rot fruit of pear with impaired volume more than 5% of total fruit volume from those less than 5%. Source

Taniwaki M.,Hiroshima University | Tohro M.,Applied Vibro Acoustics Inc. | Sakurai N.,Hiroshima University
Postharvest Biology and Technology

The ripening speed of the melon cultivar 'Miyabi-Haruaki' was determined by monitoring its elasticity index (EI) with a nondestructive acoustic vibration method. EI was determined by the formula EI = f2 2 ṡ m2 / 3, where f2 is the second resonance frequency of a melon sample, and m is the mass of the sample. The speed of ripening, i.e., ΔEI/day, was determined to be 0.36 × 104 kg2/3 Hz2 d-1, which was lower than the ripening speeds of previously studied melon cultivars 'Andes' and 'Quincy' (0.39 × 104 kg2/3 Hz2 d-1 and 0.50 × 104 kg2/3 Hz2 d-1, respectively). Using a sensory panel test, the period of optimum ripeness of the melons was determined to be 5.3-7.1 × 104 kg2/3 Hz2. Nondestructive determination of the period of optimum ripeness in terms of the EI can be useful for estimating the shelf-life of melons. In addition, by determining the ripening speed, the time required for a melon to reach optimum ripeness can be predicted. © 2009 Elsevier B.V. All rights reserved. Source

Terasaki S.,Applied Vibro Acoustics Inc. | Sakurai N.,Applied Vibro Acoustics Inc. | Sakurai N.,Hiroshima University | Kuroki S.,Kobe University | And 3 more authors.
Postharvest Biology and Technology

We have proposed a new interpretation of fruit softening. This was accomplished by generating a hypothesis that probabilities of decay of fruit structure obey the Weibull probabilistic model that has been used in the field of reliability engineering. The elasticity of individual kiwifruit after harvest was continually and nondestructively measured until decomposition by using a laser Doppler vibrometer. The obtained decreasing pattern of elasticity of individual fruit was complex, diverse, and inhomogeneous. Nonetheless, it was satisfactorily explained by a tandem combination of 2 Weibull models involving 4 types of parameters: "shape" related to probability; "scale," to velocity of decay; "location," to time lag; and "mixing ratio," to contribution of the 2 models. Averages of location, shape, and mixing ratio parameters obtained by the measurement of 33 fruit were significantly different between the 2 models, but the scale parameter was not. The results suggested that the complex softening patterns of individual kiwifruit could be described using the tandem model of Weibull distribution, and that the softening process of kiwifruit consisted of at least 2 independent decay phases that are characterized by 2 of 5 parameters: location and mixing ratio. Commencement of the first decay phase could be caused by ethylene treatment after harvest, and the second one spontaneously triggered after a certain time lag. © 2013 . Source

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