Low frequency ultrasonics for texture measurements in carrots (Daucus carota L.) in relation to water loss and storage
M. Nielsen, H. J. Martens and K. Kaack
Postharvest Biology and Technology, Volume 14, Issue 3, 1998, Pages 297-308.
1998
บทคัดย่อ
The use of low frequency ultrasonics for evaluation of carrot texture was
studied. Carrots were pretreated for 24 h in distilled water and either dried
at 25°C
for periods from 0 to 320 min or stored at 100 or 97% relative air humidity for
19 weeks. Uniaxial compression, microscopy, and analyses of density and dry
matter provided results for evaluating relationships between texture and ultrasonic
parameters. The loss of water from turgid carrot tissue did not cause
significant change in compressive Young's modulus (ECY) and
fracture work (J). The results indicate that the preliminary loss of
water caused a decrease in compressive ECY and J. At a
water loss >5%, the results indicate an increase in compressive ECY
and J. The loss of water in the drying experiment had only a small
effect on the velocity (v) and attenuation (
)
of ultrasound. The results indicate at the beginning of the drying period an
increase in v and decrease in .
This was followed by a decrease in v and increase in .
ECY decreased, while strain (
)
at failure increased during the storage period, especially after storage at low
humidity. Studies with scanning electron microscopy and light microscopy
comparing fresh and stored tissue indicated that low humidity induced shrinkage
of the cell content, changes in wall structure and development of intercellular
air spaces. The v of ultrasound decreased during storage at low humidity
contemporary with changes in the mechanical and microstructural properties.