Colour characteristics
Colour measurement of sound and degraded straw was carried out by using Hunter Colorimeter fitted with optical sensor (Hunter Associates Laboratory Inc., Reston, VA, USA) on the basis of CIE L*, a*, b* colour system as described by Sharma and Gujral (2010). The total colour difference (ΔE) was calculated by applying the following equation:
image
where L* represents lightness; a* represents redness and b* represents yellowness.