Evaluation of textural properties of mango tissue by a near-field acoustic method
Marc Valente, and Jean Yves Ferrandis
Postharvest Biology and Technology Volume 29, Issue 2 , August 2003, Pages 219-228
2003
บทคัดย่อ
A near-field acoustic (NFA) method was applied to characterize viscoelastic properties ofmangopulp tissue. The developed sensor was a stepped horn consisting of a cylindrical body and a coupled cylindrical tip to be inserted into the pulp sample. The properties of the pulp altered the mechanical resonance of the horn and the electrical resonance of the piezoelectric element, which served as both input and output port. The measured acoustic parameters represented the shift of the resonance frequency (∆f) and the attenuation of the peak amplitude (∆(1/Z)) of the probe when its vibrating tip was immersed in air, the reference medium, and then inserted into the pulp sample. Acoustic testing was carried out on each fruit at four locations evenly distributed in the middle parenchyma tissue of an equatorial section. The acoustic data were then compared to the 10 mm depth penetration force values obtained for the same four pulp locations. The results obtained for 45 mangoes with a wide range of maturity showed that ∆f was very sensitive to thequalityof the probe-medium interface, especially for unripe fruit, and poorly correlated with puncture test values. In contrast, the acoustic parameter ∆ (1/Z) was significantly correlated withmangopulp firmness Fp (r=0.92) assessed by puncture test. The relationship between these two parameters was slightly improved by a hyperbolic equation (r=0.95). The NFA method developed appears to be a promising tool for assessingmangopulp texture and for following texture changes during fruit ripening.