raspberry leaf-enriched chocolates ranged from 0.28 (MC1%) to 0.88
(DC3%) mg CyE/g of chocolate. The effect of chocolate enrichment with
the addition of raspberry leaf extract showed wide variations in terms
of the proanthocyanidin content. Compared to plain chocolates only
the addition of 3% of concentrated extract (in milk and dark chocolates)
and freeze dried raspberry leaf extract (in semisweet chocolate) slightly
increased the proanthocyanidin content of enriched chocolates. Higher
inconsistencies were observed among the flavan-3-ols content determined
using the vanillin and the p-DAC assay. As opposed to the
flavan-3-ol content determined using vanillin assay, which mainly
slightly increased after the addition of raspberry leaf extract to chocolates,
the flavan-3-ols content determined using the p-DAC assay even decreased
in the chocolates containing raspberry leaf additions. The discrepancies
among the results may be the result of a high variability and
structural diversity of flavan-3-ols in the substrate (chocolate+raspberry
raspberry leaf), as well as method of non-selectivity or interferences
which very often occur in colorimetric assays. Moreover it is well
known, that polyphenols have a strong inclination to form complexes
with proteins, polysaccharides, and alkaloids, in both unoxidized and
oxidized forms (Hagerman & Butler, 1981). The presence of different
bioactive compounds, deriving fromboth cocoa and raspberry leaf (proteins,
minerals, and polysaccharides, Table 2) may have influenced the
final results of these assays and cause the observed fluctuations in the
results. Based on the obtained results of vanillin assay, even the addition
of 1% of concentrated extract might significantly affect the overall
flavan-3-ols content of functional chocolates.