| Summary: | 碩士 === 國立中興大學 === 農業機械工程學系 === 86 === This study evaluate the firmness index through some parameters,
such as resonant frequency, mass and firmness. The decaying
model was established for the elastic modulus vs. time and the
derivation of decreasing mathematical model of resonant
frequency during storage time by regression analysis method. The
decaying model will use to evaluate the Mango''s stiffness and
storage time during selling process. Mangoes were stored at a
constant temperature (13℃) and relative humidity (RH 88%)
cabinet. The mango samples were excited by the impact hammer
each day. Frequency response signal was acquired with
accelerometer and then the first and second resonant frequencies
analyzed through FFT method. The changes of mass and frequencies
were recorded each day. The total measurements of whole process
is lasted for days. The elastic modulus of flesh was obtained
through the slope calculation of force-deformation curve through
the compression test. According to those data, the firmness
index of mangoes can be predicted. Besides, the decaying
characteristics of elastic modulus with respect to time was also
investigated. After four different models were analyzed through
the regression, the best model ,f1^2*m^(2/3)*ρ^(1/3),was
obtained ,which has the determination coefficient of 0.5288 and
standard deviation of 1.6733. From the experimental results, the
f^2*m^(2/3)*ρ^(1/3) model can be used as the firmness index for
mangoes. This firmness index model has good correlation
relationship with the first resonant frequency while mango was
excited by the impulse.ehe exponential decaying model (e^-(kt))
of elastic modulus during storage is not suitable for mangoes.
The better fitted the exponential model for the mangoes is e^-(
kt^(3/2)), which has the determination coefficient as 0.9747 and
standard deviation of 0.128.
|
|---|
