Biomedical Engineering Reference
In-Depth Information
Fig. 2.3
Molecular weight
distribution of native wheat
storage (gluten) proteins
(Modi fi ed from [
73
] )
comparison with total glutenins; the HMW-GS combination 1Dx5 + 1Dy10
appears to produce higher GMP concentrations than 1Dx2 + 1Dy12 [
73
] .
Rye storage proteins have a strongly different MWD as compared to wheat.
Although rye shows higher proportions of aggregative to monomeric storage pro-
teins than wheat (Table
2.7
), the proportions of polymers is much lower (~23%) and
the amount of GMP (~5 mg/g flour) strongly reduced [
75,
76
] . The de fi ciency of
polymeric proteins is balanced by the higher proportion of oligomers (~30%), whereas
the proportion of rye monomers (~47%) is similar to that of wheat. Obviously rye
storage proteins consist of many more chain terminations (e.g., g -75 k-secalins,
y-type HMW-secalins) and less chain extenders than wheat, which apparently
prevents gluten formation during dough mixing. Information about the MWD of
native barley and oat proteins is not yet available.
2.3.2.4
In fl uence of External Parameters
Many studies have substantiated that both structures and quantities of storage pro-
teins are exposed to a continuous change from the growing period of plants to the
processing of end products. Because of the importance of wheat as a unique “bread
cereal,” most investigations have been focused on gluten proteins. In principle, how-
ever, the effect of external parameters is similar for all cereal proteins.
Fertilization
The supply with minerals during growing is essential for optimal plant develop-
ment. Nitrogen (N) fertilization is, in particular, important for common wheat,
because a high N supply provides a high flour protein content and thus, increased
bread volume. Fertilization with different N amounts demonstrated that the quantities
