Food Products Physical Properties of Rice Grains

The study of food preference factors such as taste, flavor, and color has achieved a certain level of results in food chemistry, and research into mechanical properties such as crispiness or chewiness and texture is following.
As for rice, physical properties at the level of the individual grain have already been studied with material testing machines for determining the relation between the state of the texture of the grain, moisture concentration in cooked rice, and mechanical properties such as compression load, compression displacement and compression elasticity (determined by compression load-displacement curves).
The Shimadzu Autograph is a high performance universal testing machine well suited to the measurement and testing of mechanical strength and behaviors of materials and parts ranging from metal, rubber and plastics to vehicles, electronics, foods, medical supplies etc. Furthermore, the calculation of any specific characteristic values is made possible by the automatic computer processing system which controls measurement, operation, and data processing.
The following presents the results of compression tests performed with the Shimadzu Autograph on unpolished, half-polished and polished individual grains of rice available on the market.

Compression tests of rice grains

Testing machine

(1) Shimadzu Autograph
(2) Compression test attachment for 100kgf

Test conditions
(1) Loading speed: 1mm/min
(2) Loading range: 10kgf/full scale

Figs.1,2, and 3 show compression load versus displacement curves and result of data processing, and Table 1 is a summary of the measured data. These data clearly demonstrate that the physical properties vary depending on the presence or absence of skin on raw rice.
Compression load versus displacement curves are easily obtained for loads until the rice grain is broken. In addition, a micro specimen such as a rice grain can be tested safely and efficiently by selecting an appropriate sensitivity from the values among the detector's sensitivity range.

Table 1 Result of Measurement
Sample Max. compression load Displacement Elasticity
Unpolished rice 7.7kgf 0.13mm 66.3kgf/mm2
Half-polished rice 4.6kgf 0.07mm 75.2kgf/mm2
Polished rice 5.3kgf 0.08mm 78.4kgf/mm2

For Research Use Only. Not for use in diagnostic procedures.

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