2009_Book_FoodChemistry

700 15 Cereals and Cereal Products
Table 15.26. Reduced (GSH), oxidized (GSSG) and protein-bound glutathione (PSSG), total glutathione (GSS)
as well as cysteine (CSH) and CSS a
Wheat cultivar Ash (wt. %) Concentration (nmol/gflour)
GSH GSSG PSSG GSS CSH CSS
DNS 0.78 100 n.a. n.a. 279 13 159
Maris Huntsman 0.68 81 n.a. n.a. 232 9 145
Kanzler 0.62 35 n.a. n.a. 180 8 118
Fresco b n.a. 31 24 131 210 n.a. n.a.
Norman b n.a. 74 15 73 177 n.a. n.a.
Mercia b n.a. 74 27 102 230 n.a. n.a.
Haven b n.a. 18 20 89 147 n.a. n.a.
a CSS consists of free cysteine, cystine and cysteine, which is linked with wheat proteins only via disulfide bridges
but not via peptide bonds.
b Degree of grinding 64–68%.
n.a.: not analyzed.
Table 15.27. Glutathione concentration as a function of
the degree of grinding
Wheat Ash Glutathione a
cultivar (w/w%)
GSH Total b
CWRS c 0.54 16 172
0.71 35 348
1.44 60 575
DNS c 0.59 41 175
0.78 110 345
1.57 215 657
Maris 0.55 20 185
Huntsman 0.68 94 273
1.73 210 435
GSSG + PSH ⇋ GSSP + GSH (15.5)
Cysteine is also rheologically active and cystine
after disulfide exchange, e. g., with PSH. To
identify the disulfide bonds in gluten proteins,
which are cleaved by endogenous GSH by disulfide
exchange, flour was kneaded with added
[ 35 S]-GSH. The use of high specific radioactivity
allowed the additive to be kept very low in comparison
to the GSH present in flour. The disulfide
bonds labelled by [ 35 S]-GSH are cleaved by the
endogenous GSH according to the reaction given
a Calculated as GSH in nmol/g based on the dry
weight.
b Sum of GSH, GSSG, and GSSP.
c Marks of origin: Canadian Western Red Spring
(CWRS), Dark Northern Spring (DNS).
urements of flour/water dough show the effect of
GSH (Fig. 15.16). At 124 nmol/g, the concentration
of GSH in the sample of flour is relatively
high. The strength of the dough decreases
with the addition of 100 nmol/g GSH. GSSG is
also active but not as much as GSH (Fig. 15.16)
because it first has to be reduced to GSH, e. g.,
by proteins with free SH groups (PSH, cf. Formula
15.5), before it can depolymerize aggregated
gluten proteins as shown in Formula 15.4.
Fig. 15.16. Influence of reduced (GSH) and oxidized
glutathione (GSSG) on the rheological properties of
wheat dough (according to Hahn and Grosch, 1998).
Tensile tests with dough made of 10 g of DNS flour
(0.76% ash, 15.5% protein, 124 nmol/g GSH),water,
2% NaCl and the following additives (nnol/l flour):
GSH (100; ◦–◦), GSSG (50; •–•), control without additive
(—). F: force, L: distance