Noncontact ultrasound for mechanical property of cheese . . .
Table 6—Linear parameters for the relationship between
rectly related to the bulk modulus, it is significantly related with
mechanical properties, such as Young’s modulus, hardness, and
toughness, which is consistent with the findings of Benedito and
others (1999), indicating that ultrasound velocity is related to the
square root of the mechanical property values. The bulk modulus
could be assumed to be related to the Young’s modulus; however it
is not easy to find the physical reasons for the relationship between
other mechanical properties, such as hardness and toughness and
the bulk modulus which is a direct determinant of the ultrasound
velocity. In addition, the power of noncontact ultrasound is small
enough so that the rate of strain is linearly related to stress. Hence,
quantitative comparison between ultrasound parameters and the
mechanical properties defined by the large strain assumption is
not possible. Extended experiments with thoroughly characterized
samples would be necessary to investigate the precise physical
meaning of the relationship.
The correlation between the ultrasound attenuation coefficient
and the mechanical parameters showed high variability. Even
though the attenuation coefficient is assumed to be related to the
complicated combination of viscosity, density, and ultrasound ve-
locity, its sensitivity to sample surface unevenness, minor surface
defects, porosity, and uneven component distribution in sample
materials also make it difficult to find the relationship with the
mechanical property of cheeses.
ultrasound velocity and mechanical properties of cheeses
Parameter = 0 + 1×Velocity + 2×Velocity2
Content Young’s modulus
Hardness
Toughness



33395.28
–420.72
0.134
0.915
170.09
109811.31
–140.11
0.045
24830.96
–31.57
0.01
0
1
R22
0.995
14.36
0.995
2.74
SEEa
a
Standard error of estimation
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apid food thickness measurement using noncontact air insta-
R
bility ultrasound technique was possible with an accuracy of
above 99.9% (SE = 0.089 mm). Ultrasound parameters of different
types of cheeses could be measured and also correlated with me-
chanical properties of cheeses. Whereas the ultrasound velocity
showed high correlation (R2 > 0.9) with mechanical properties of
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Even though mechanical properties of different types of cheeses
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Acknowledgments
The authors would like to thank Dr. Virendra M. Puri for his ad-
vice on mechanical property measurement and use of the Instron
unit.
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URLs and E-mail addresses are active links at www.ift.org
Vol. 68, Nr. 7, 2003—JOURNAL OF FOOD SCIENCE 2247