in Table II. It is quite obvious that the particular
pigment patterns affect colour stability. Anthocyanins
are most stable in their flavylium cation form
at acidic pH (pH 2), losing colour at pH 3Ð4
through hemiketal formation further being transformed
into quinoidal bases (Stintzing and Carle,
2004). Cabrita et al. (2000) observed an absorption
decrease of anthocyanin-3-glucosides until pH 6
being increased at alkaline pH. To get a clearer
insight into eggplant and violet pepper appearance
as affected by pH increments, colour stability values
according to Dougall et al. (1997) were calculated
(Table II), with higher numbers translating
into improved pigment retention. These ratios
were lower for violet pepper than for eggplant, especially
between pH 1 and pH 6 (Table II). ΔE*
values (Gonnet, 1999) were also measured to
monitor colour differences which were generally
higher for violet pepper (Table II). These findings
demonstrate that ΔE* values present a more sensitive
tool to assess colour alterations than CS values,
because the latter exclusively consider absorptivity
values. Hence it follows that despite
acylation pigment extracts from violet pepper exhibited
a lower tinctorial strength. Inspection of
individual chromatic data revealed that lightness
L* increased in less acidic solutions being more
intense between pH 1 and pH 3.5 complying with
the CS values (Table II). Hue angle values for eggplant
were located in the red region and reached
60.9 with increasing pH value, equivalent to an