- Red radish anthocyanin extract (RAE) was investigated for coloring brined
cherries as an alternative to FD&C Red No. 40. Red radish (Raphanus sativus L.)
anthocyanins were extracted from liquid nitrogen powdered epidermal tissue using
acetone, partitioned with chloroform, and isolated using C-18 resin. The monomeric
anthocyanin content was determined by pH differential to be 154 ± 13 mg/100 g of
epidermal tissue (on pelargonidin-glucoside basis). The major pigments were
identified as pelargonidin-3-sophoroside-5-glucoside monoacylated with p-coumaric
or ferulic acids by HPLC and spectral analyses. Primary and secondary bleached
cherries were sweetened to 40° Brix (pH of 3.50), and colored using two
concentrations of RAE (600 and 1200 mg/L syrup, designated Cl and C2) and
FD&C Red No. 40 (200 ppm). Color was measured for both cherries and syrup.
Reflectance measurements (CIE L*, a*, b*), chroma and hue angle, showed that
RAE imparted red color to the cherries and syrup extremely close to that of FD&C
Red No. 40. RAE C2 gave the primary bleached cherries the closest color
characteristics (L*= 18.20, a*= 20.00, b*= 8.47) to FD&C Red No. 40 (L*= 18.00, a*= 24.35, b*= 12.13). RAE Cl gave the secondary bleached cherries the closest color
characteristics (L*= 15.27, a*= 16.21, b*= 5.21) to FD&C Red No. 40 (L*= 16.38,
a*= 19.91, b*= 8.99). Color and pigment stability of secondary bleached cherries
were evaluated during a year of storage in the dark at 25°C. Monomeric anthocyanin
degradation followed first-order kinetics and the half-lives were 29 and 33 weeks for
syrups colored with RAE Cl and RAE C2, respectively. However, cherry color
showed no significant changes in hue, color intensity nor lightness during storage.
Color changes of syrup samples over time were dependant on anthocyanin
concentration, higher anthocyanin concentration exerted a protective effect on color
stability. Haze formation was observed in syrup samples colored with RAE, possibly
due to pigment polymerization.
Syrup samples colored with RAE and FD&C Red No. 40 were also exposed
to light for a year at 25°C. Light had a small but significant effect on L*, a*, and
monomeric anthocyanin content.
From color and pigment stability data and visual observations we concluded
that RAE was effective in coloring secondary bleached cherries with results very
similar to those of FD&C Red No. 40 for 6 months of storage.