Overview
ISO 11747:2012 specifies a laboratory method to determine the resistance to extrusion of milled rice kernels (parboiled or not) after cooking. The test measures the force required to push cooked rice through a perforated plate using a dynamometer and an extrusion cell; results are reported as mean force per unit area (kg/cm²). This standard is used to assess cooked-rice texture related to processing, quality control and product specification.
Key topics and technical requirements
- Scope: Milled rice (parboiled or non-parboiled), cooked under defined conditions and tested for extrusion resistance.
- Sample moisture: Laboratory sample moisture must be (13.0 ± 1.0) % determined by ISO 712 before testing.
- Cooking procedure: For each test, weigh 20 g rice + 38 ml deionized water in borosilicate beakers; steam-cook on a perforated plate with vigorous boiling for 20 min, remove heat and stand 10 min, then cool 1 hour at 20–25 °C.
- Portioning: Form three portions ≈ 17 g from each cooked cylinder; test six portions per sample (two beakers × three portions).
- Extrusion apparatus:
- Dynamometer with loading cell ≥ 50 kg, constant speed 10 cm/min, data acquisition ≥ 5 samples/s.
- Extrusion/parallelepiped cell with hole area 7.5 cm², perforated plate 3 mm thick with 6.0 mm diameter holes and 7.0 mm pitch, piston clearance ≈ 0.5 mm.
- Ottawa cell is cited as an example of suitable equipment.
- Calculation & units: Mean of six measurements divided by parallelepiped hole area (7.5 cm²). Report in kg/cm², to two decimal places.
- Precision:
- Repeatability limits (r): 0.056 kg/cm² (non-parboiled), 0.082 kg/cm² (parboiled).
- Reproducibility limits (R): 0.107 kg/cm² (non-parboiled), 0.219 kg/cm² (parboiled).
- Test report minimums: sample ID, sampling method, reference to ISO 11747:2012, operating details, test results, any repeatability checks.
Practical applications
- Quality control in rice milling and processing - objective measure of cooked-rice firmness/texture for grading and batch acceptance.
- Product development & R&D - compare cooking and texture effects of varieties, parboiling processes or formulation changes.
- Regulatory and specification compliance - include in product specifications or contracts where cooked-rice resistance is a requirement.
- Breeding and screening - assist plant breeders and food scientists evaluating cooked-texture traits.
Who should use this standard
- Rice mill laboratories and processing plants
- Food testing and sensory labs combining instrumental and sensory data
- Agricultural research institutes, breeders and product developers
- Regulatory bodies and certification laboratories
Related standards
- ISO 712 - moisture content reference method (required).
- ISO 7301 - rice specification and terminology.
- ISO 24333 - recommended sampling for cereals and rice.
- ISO 5725-2 - statistical methods for repeatability and reproducibility (used in precision assessment).
Keywords: ISO 11747:2012, rice kernel resistance to extrusion, cooked rice testing, milled rice, parboiled rice, dynamometer, extrusion cell, Ottawa cell, laboratory method, cooked-rice texture.
