The colour loss was calculated from the values of percent colour
retention at initial and final treatments. Polymeric colour was
determined using the bisulphite bleaching method (Giusti &
Wrolstad, 2001). The beverage solutions were bleached with sodium
metabisulphite, using water as a control. The polymeric colour
was measured at initial and final of treatments, expressed as
DPC. L⁄
, a⁄
, b⁄ colour values of the beverage solutions were measured
at initial and final of treatments using a Minolta Chroma
CR-210 Colourimeter (Gonnet, 1998). Chroma (C⁄ = [(a⁄
)
2 + (b⁄
)
2
]
1/
2
) and hue angle (h = arctan (b⁄
/a⁄
)) were calculated from a⁄ and
b⁄
. Total colour difference (DE) was calculated through the equation
of DE = [(DL⁄
)
2 + (DC⁄
)
2 + (DH⁄
)
2
]
1/2. The reaction rate constants
(k) and half-life time (t1/2) values were calculated
according to Kirca and Cemeroglu (2003) following a first order