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
M.