Podsędek et al. (2008) examined the effects of water to
cabbage ratio and blanching time on the polyphenol content
of Kissendrup and Koda red cabbage varieties upon
the application of conventional water blanching. Reductions
of up to 50% in water volume led to better retention of
phenolics as compared to when blanching was carried out
using a 2:1 ratio of water to cabbage. Conversely, shortening
the conventional blanching time from 20 to 10min
increased the retention of phenolics by only 3.8–6.7%. This
suggests that polyphenol losses upon blanching could be
attributed to their respective solubility and stability, which
would be highly influenced by the type of the blanching
environment (steam or hot water) and also its corresponding
volume to facilitate the leaching and transfer of phenolic
compounds from the cell interior to the blanching
environment. Also it is worth noting that free polyphenols
leach out faster in the water when compared with
bound polyphenols. As blanching temperatures increase,
a higher loss in phenolic compounds is expected; however,
the effect of blanching time does not necessarily follow
a similar trend. It seems that for a given blanching
treatment, losses in phenolic compounds initially increase
as blanching time proceeds, but only up to a certain point,
after which a plateau state is attained and longer blanching
times do not correspond to higher losses of phenolic
compounds. This highlights the role of heat in degrading
cabbage cellular material leading to the leaching of polyphenols.
A higher level of phenolic losses would require
the application of a higher temperature rather than a longer
blanching time for a given blanching treatment, thus
emphasizing the role of heat in causing phenolic mass
transfer. Conversely, blanching time profiling with respect
to polyphenol losses would be of significant importance
in identifying those times that correspond to minimum
polyphenol losses while also attaining appropriate quality
attributes such as color and texture. At a domestic or
industrial level, the first 6–8min of blanching are detrimental
with respect to a number of quality parameters
including phenolic content, and there is a need for more
detailed studies at both processing and consumer levels
to examine whether the polyphenols, with their established
health benefits, are being largely compromised by
perceived consumer quality attributes for attaining certain
textures and colors of vegetables upon blanching.