Test Method: Compression With Strain Control
Cooked rice suits a strain-controlled compression test. The probe presses into the rice, and the peak force and return curve give hardness and stickiness. RapidTA's application data recommends a Ø 36 mm cylindrical probe for rice, with the test mode set to strain control.
Related applications include rice pudding (a Ø 40 mm cylindrical probe is recommended) and dry pasta (using the noodle snap fixture, with the test mode set to distance control).
Key Sample Prep Points
Cooked rice's hardness changes with resting time and temperature, so sample prep is the key to repeatability. Fix the following before testing:
- Cooking water ratio and time: [TBD]
- Resting time and temperature after cooking: [TBD]
- Sample container and portion size: [TBD]
- Number of repeats per sample: [TBD]
Reading the Data: Hardness and Stickiness
Hardness is the positive peak of the compression curve. A higher value means firmer grains and a chewier bite.
Stickiness is the negative-force area on the return curve, reflecting the adhesion between the grains and the probe as it lifts away. Stickier rice feels moister, but too much can hurt separateness.
When comparing rice varieties or cooking conditions, look at hardness and stickiness together, and use the mean and standard deviation of repeats to judge whether a difference is real.
Frequently Asked Questions
- How long should cooked rice rest before testing?
- Resting time affects hardness, so use the same resting time and temperature for every group you compare, and record it in the report. Set the exact conditions to your research purpose; the parameter recommendations above are marked [TBD].
- Should hardness and stickiness be read together?
- Yes. Looking at hardness alone can miss how much the grains stick together, and two rice samples with similar stickiness can still differ in hardness in ways that change how the mouthfeel is judged.
Further Reading
Related Test Actions
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