The results from the DMAC assay showed that the total concentration
of procyanidins decreased with the time in both chambers,
PACs being present in less concentration over time in chamber B
(Table 1). Thus, non-irradiated syrup (control) had a concentration
of 4130 ± 50 lg/ml, which is significantly higher than that found in
gamma-irradiated syrup (3460 ± 80 lg/ml). However, this only
meant a loss of only about 16%.
On the other hand, the concentration of PACs in samples stored
at 25 C/60% RH (chamber A) significantly differed between the
different months of storage, with a total loss over 60% after
6 months. The loss of PACs in samples stored at 40 C/75% RH in
chamber B was higher after 6 months, the total loss of PACs being
around 80%. These results from the DMAC assay agreed with
results from HPLC–ESI-QTOF-MS quantification. Overall, using the
latter method and compared with the control samples, the total
loss of PACs was over 65% in chamber A whereas in the chamber
B the total loss was over 92%. Although the degradation pathway
was not investigated in the present study, they could be related
to their oxidation, hydrolysis or isomerization (Chang et al., 2006).
Although, DMAC assay is consider to be the best analysis available
to perform an overall quantification of flavanols (Boudesocque
et al., 2013), it is important to complement these results with the
analysis of each individual compound, since the behaviour depend
on the chemical structure, even stereochemistry, such as our
results found for procyanidin B isomers.