Rice and easy standard texture measurement

Rice, a foodstuff of all times and ages, is the foundation of the diet for billions of people. As well as being a basic and widely consumed foodstuff in its own right, rice is increasingly popular as a component of processed and convenience foods.

But with over 1,000 varieties, identifying the one with optimal amylose content, gel consistency and gelling temperature to match the desired eating texture can be difficult.

Alongside the release of a new International Standard (ISO 11747) for rice testing, Stable Micro Systems has developed a new Rice Extrusion Rig – for use with Plus texture analysers – which conforms with the standard testing specifications. Growers, processors and food manufacturers can now objectively and accurately analyse the resistance to extrusion of rice samples, enabling them to select the cultivars which satisfy both their own textural requirements and the demands of customers and consumers.

What’s the testing solution?

Just one of a range of attachments for testing pasta, rice and noodles, the new Rice Extrusion Rig provides a simple, quick, accurate and economical method for measuring the eating qualities of rice, but also includes additional design features specifically focused on making the testing cell more quickly removable and replaceable between tests. This standard is the outcome of interlaboratory testing organised in 2010 by UNI involving nine international laboratories and was prepared by the ISO/TC34 Technical Committee for Cereals and Pulses. 

The sample is tested after cooking (parboiled or not parboiled) under specified conditions.  A small sample is placed in the testing cell of the rig. The rice is pushed down by a plunger of similar cross-section to the cell therefore forcing the rice to be compressed before extruding through the holes in the base extrusion plate on which the sample is located. Resistance to extrusion is measured as the ease of pushing cooked rice through this perforated plate using compression and shear. The mean force required to extrude the sample over the plateau region of its curve is divided by the testing area of the extrusion plate and is recorded in kg/cm2.

“Food palatability is determined by many factors,” says Jo Smewing, applications manager at Stable Micro Systems, “and texture is the one that can be difficult to measure objectively and repeatably. The challenge is magnified when we take into account regional preferences.

In the Middle East and south Asia, dry and flaky rice varieties are preferred. But in Japan, the Republic of Korea and northern China, consumers opt for moist and sticky. Being able to complement sensory testing with instrumental evaluation methods means the industry can now perfect aroma, appearance, taste and texture, all of which are critical to consumer acceptance.”

The Rice Extrusion Rig helps to overcome the issues of lengthy, labour-intensive, difficult sensory tests.