6B Peptides 201
Fig. 6B.4Flowchart for the interpretation of both spectral data and OPA-fluorescence response.
aBand 1, spectral band (201–207 nm);bBand 3, spectral band (276–280 nm);cC.i.convexity inter-
val (distance between the inflection points before and after the maximum in the original spectrum);
dMin, minimum in the original spectrum (from Moreno-Arribas et al. 1998a, with permission)
procedures (Table 6B.1). Since the soluble fraction in TCA is not the same as the
soluble fraction in ethanol or that obtained by ultrafiltration using membranes of
different pore size, it is very difficult to compare the results reported in the literature.
Moreover, in most of the cases, the authors express the results in different units. In
this way, some results are expressed as mg/L of wine, percentage distribution of
amino acids in the total fraction, ratio of peptide nitrogen/total nitrogen, number of
residues of a peptide or a specific fraction, etc.
Table 6B.2 summarizes the data available in the literature on peptides contents
of musts, wines and related substrates such as autolyzed yeasts obtained under
winemaking conditions. This table also shows the fractions studied by the different
authors, the type of product, the analytical methodology, the results obtained and
the purpose of their research.