Produce Color and Appearance 207
in the visible range from 450 to 600 nm were recorded during storage of the samples.
The profile of anthocyanins was also monitored using HPLC. All phenolic acids
improved color and its retention in the four investigated juices during the 103 d of
storage compared to untreated samples. Sinapic acid was most effective in strawberry
juice, leading to color intensity after storage higher than the initial value. The
effectiveness of ferulic and synaptic acids was equal in the case of raspberry juice.
Rosmarinic acid showed the best effect in lingonberry and cranberry juices. Unen-
hanced strawberry and raspberry juice color was not detectable after 36 and 51 d,
respectively, under experimental conditions. The color of lingonberry and cranberry
juices was 33 and 19%, respectively, of its original intensity under the same condi-
tions. In general, the addition of grape skin and black carrot extracts to the four
juices significantly increased initial color intensity but led to some problems later.
The presence of grape skin extract caused brown discoloration of strawberry juice,
leading to total color deterioration after 51 d. The addition of commercial non-
anthocyanin rosemary extract caused similar problems. HPLC results showed a
decrease of total peak area of anthocyanins. Untreated raspberry and strawberry
juices retained after storage only about 1% of their initial anthocyanins. Lingonberry
and cranberry juices contained 13 and 10%, respectively. The addition of phenolic
acids to the juices resulted in new HPLC peaks. Identification of these peaks was
not conducted in this study.
It is believed that the decrease of the content of anthocyanins during aging of
red wine is due to an interaction with pyruvic acid and formation of visitins A (Vivar-
Quintana et al., 2002). Antioxidant and biological activities of three most abundant
anthocyanins in red wines and relevant visitins A were investigated by Garcia-Alonso
et al. (2004). Visitins A were synthesized according to previously described methods
of Romero and Bakker (1999). Delphinidin-3-glucoside, petunidin-3-glucoside, and
malvinidin-3-glucoside exhibited higher antioxidant activity than the corresponding
visitins A.
Characterization of 20-, 3-, and 1-year-old Port wines was conducted by high-
resolution NMR and high-resolution diffusion-ordered spectroscopy (DOSY) in
order to identify changes during storage (Nilsson et al., 2004). High-resolution
DOSY allowed identification of an increased number of compounds. The wine
samples of various ages differed in their content of organic acids, some amino acids,
and aromatic species. A significant decrease of high molecular aromatics in the
oldest wine is consistent with the formation and precipitation of anthocyanin-based
polymers during aging of red wines.
7.4.4 PROGRESS IN ANALYTICAL METHODOLOGY
The rapid progress in analytical methodology allows improved, faster, and more
precise qualitative determination of anthocyanins. The application of HPLC to ana-
lyze anthocyanins was reported and reviewed previously (Giusti et al., 1999; da
Costa et al., 2000; Merken and Beecher, 2000; Chandra et al., 2001; Mullen et al.,
2002). There are still major challenges related to preparation of the samples for
analysis, especially changes of anthocyanins during hydrolysis and lack of reference
compounds.