Identification of the major drivers of 'phenolic' taste in ... - GWRDC

AWRI: Identification Of The Major Drivers Of ‘Phenolic’ Taste In White Wines
A.2 High speed Counter-current Chromatography
A.2.1 Introduction
High speed counter-current chromatography (HSCCC) is a partition chromatography process that
separates analytes through high speed mixing and separation between two immiscible liquid phases. The
process offers numerous advantages over conventional preparative chromatographic methods such as
good sample recovery both in terms of purity and yield, zero irreversible adsorption and high loading
capacity.
HSCCC is particularly suited to the isolation and fractionation of phenolic compounds as their varied
sizes and degree of hydroxylation affects their hydrophobicity and therefore their relative affinities for the
(generally) polar mobile phase and non-polar stationary phase. Indeed, HSCCC has previously been used
to fractionate flavanols (Wang et al. 2008), flavonol glycosides (Zhang et al. 2007), flavonoids (Costa
and Leitao, 2011) and hydroxycinnamic acids (Maier et al. 2006), but only on an analytical scale.
HSCCC systems have the potential to achieve higher loading capacities than do traditional preparative
chromatographic approaches that utilise solid supports with finite binding capacities. Therefore HSCCC
could allow the relatively large amount of phenolic material required to undertake replicated sensory
testing to be isolated in a relatively small number of runs.
The effectiveness of any HSCCC solvent system in separating analytes from a complex mixture depends
on the analytes having different partition coefficients between the two immiscible layers that form when
the solvents are mixed. If the partition coefficients are the same then the compounds will co-elute. On the
other hand, if a compound solely partitions into one phase or the other then it will either elute close to the
solvent front, or alternatively it will be retained in the stationary phase. In the former case, the compound
of interest will usually will co-elute with other compounds with similarly extreme partition coefficients,
or in the latter case, it will never elute. Therefore the most important step of HSCCC optimisation
involves finding the optimal mix of solvent components that best differentiate the compounds to be
separated on the basis of their partition coefficients.
To this end, a white wine HSCCC method was developed that provided enough caftaric acid and Grape
Reaction Product to allow their sensory properties to be formally assessed.
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