The colour of blueberries was measured in reflected light using a MiniScanTM XE Plus spectrophotometer (HunterLab) coupled with a circular optically clear glass sample cup (HL#04-7209-00). The sample cup filled with fifty berries was positioned over the sample port and the colour of blueberries was read through the glass bottom of the sample cup. After the measurement, the sample cup was emptied, refilled, and the colour of blueberries was measured again. The procedure was conformed to standard test method (ASTM, 2013). Colour parameters were L* (L* = 100 means white; L* = 0 means black), a* (+a* means redness; a* means greenness), b* (+b* means yellow; b* means blue). Colour
coordinates were determined in the CIE L* a* b* space for the 10 standard observer and the D 65 standard illuminant. The colorimetric ratio (a* b*1) was computed to represent the ratio