**2. Measurement of kernel elongation ratio**

Cooked kernel elongation can be measured by three ways *viz*., grain elongation ratio, proportionate change, grain elongation index. Grain elongation ratio is defined as the ratio of the length of cooked rice (L2) to the length of milled rice (L1). Kernel elongation ratio indicates the proportionate change of rice grain after cooking. Sood and Siddiq [6] followed following formula to measure kernel elongation

$$\text{Proportionate change} = \frac{L\_{\text{F}} \; / B\_{\text{F}} - L\_{0} \; / B\_{0}}{L\_{0} - B\_{0}} \tag{1}$$

Where, LF – kernel length after cooking, BF – kernel breadth after cooking, L0 – kernel length before cooking, BF – kernel breadth before cooking. Grain elongation ratio is a better index of cooking quality than grain elongation index (A) or proportionate change [7].

$$\mathbf{A} = \frac{L\_2 \, ^\circ W\_2}{L\_1 \, ^\circ W\_1} \tag{2}$$

Where, L2 – cooked kernel length, W2 – cooked kernel breadth, L1 - milled rice length, W2 - milled rice breadth.

Grain elongation index is a more reliable estimate of kernel elongation during cooking [8].

$$\text{Elongation index} = \frac{BGS}{GS} \tag{3}$$

*Breeding for Grain Quality Improvement in Rice DOI: http://dx.doi.org/10.5772/intechopen.95001*

Grain elongation index values were less precise and less sensitive than elongation ratio. It needs the additional measurement of grain width, use of kernel L/B ratio instead of length offered no advantage of sensitivity since, grain expanded both length and width wise during cooking [9, 10].

After cooking length – Before cooking length Cooked rice elongation <sup>100</sup> Before cooking length <sup>=</sup> <sup>×</sup> (4)
