6B Peptides 205
Yokotsuka et al. (1975) in the soluble fraction in TCA analysis, retained in a
catioinic resin, found concentrations of 18 mg/L peptide nitrogen in a must and
22, 52 and 144 mg/L in two white wines and one red wine, respectively. These
results correspond to 2.7% of the total nitrogen of the must, 5% and 9.5% of the
total nitrogen of both white wines and 56% of the total nitrogen of the red wine.
Moreno-Arribas et al. (1996), in their study of the nitrogenated fraction soluble in
95% ethanol of musts, base wines and sparkling wines obtained from the same musts
of 9, 12, 15 and 18 months aging in bottle, estimated the nitrogen fraction as the
difference between the total nitrogen and the sum of free amino nitrogen and proteic
nitrogen. They obtained values ranging from 118.2 mg/L to 162.2 mg/L of peptidic
nitrogen in three musts, from 14.5 mg/L to 57.6 mg/L peptidic nitrogen in the four
white base wines studied and from 17.9 mg/L to 90.2 mg/L peptidic nitrogen in
the 16 sparkling wines. These values constitute 47% of total must nitrogen, from
12% to 57% of total nitrogen of the base wines and from 21% to 70% of total
nitrogen of the sparkling wines. Dos Santos et al. (2000) in the peptide fraction of
relative molecular mass from 500 to 5000 Da found a concentration of 124 mg/L
peptide nitrogen in the initial wine (base wine) and 16.3, 24.5, 32.3 and 59.5 mg/L
peptide nitrogen in the same wine after 5, 8, 10 and 15 weeks of aging with “flor”
yeasts. This nitrogen constitutes approximately 6%–21% of the total wine nitrogen.
Summarizing the data available in the literature, the concentration of peptide
nitrogen in musts range from 18 mg/L to 162.2 mg/L, corresponding to 2.7%–47%
when expressing such as total nitrogen; the concentration of peptidic nitrogen from
table wines, range from 14.5 mg/L to 57.6 mg/L in white wines and 144 mg/L in
red wines, equivalent to 12%–57% of the total nitrogen in white wines and 56%
of red wine; in sherry type wines, the concentrations are between 16.3 mg/L and
59.5 mg/L of peptidic nitrogen and in sparkling wines from 17.9 mg/L to 90.2 mg/L
of peptidic nitrogen (thus, between 21% and 70% of the total nitrogen).
In the case of peptide characterization, some of the studies of wine peptides
describe the amino acid composition of the total peptide fraction obtained using dif-
ferent extraction methods (Table 6B.1) (Yokotsuka et al. 1975; Usseglio-Tomasset
and Bosia 1990; Dos Santos et al. 2000; Alexandre et al. 2001). Other studies
(Moreno-Arribas et al. 1998a,b; Pozo-Bay ́on et al. 2005) determine the amino
acid composition of peptide fractions of different molecular sizes and the amino
acid composition of some chromatographic peaks obtained by low pressure liquid
chromatography (or open column chromatography) (Acedo et al. 1994) or HPLC
(Moreno-Arribas et al. 1998a; Desportes et al. 2000).
It is interesting to note that aspartic acid and/or asparagine and glutamic acid
and/or glutamine form part of the peptides of all the wine fractions of different
studies, independently of the type of wine or the analytical methodology employed
in the analysis. Serine, threonine, alanine and glycine appear in most of the fractions
studied while, lysine, tyrosine, valine, leucine, histidine and isoleucine has been
found in a minor extent in these fractions.
There are not many wine peptide sequences described in the literature. Table 6B.3
shows those that have been described. It can also be seen that in peptides with 2–10
amino acids, the amino acids that appear most frequently are tyrosine, proline, and
isoleucine.