The quality of wheat-based food. products, especially bread quality, is
significantly affected by the characteristics of the wheat flour, both in term of
processing quality and nutritional value. White flour, by far the most used flour
in breadmaking, derives from grinding of the grain starchy endosperm. Several
studies have demonstrated that the endosperm tissue shows significant
inhomogeneity in its chemical composition, with both quantitative and qualitative
patterns of tissue distribution observed for all its main storage components.
This project has focused on a detailed study of the spatial distributions of
proteins and starch within the wheat endosperm, how they are influenced by
genetic and environmental factors and how they affect the processing
properties of the flour. Multiple technologies, including protein/starch chemistry,
immunocytochemistry and microscopy, have been used to achieve the research
aims.
The results show a clear deceasing gradient in total protein in the endosperm
from the subaleurone toward the centre of the grain. Strong spatial gradients
were also observed in the composition of gluten proteins. These patterns were
best visualised in vivo by Immunofluorescence microscopy. The SE-HPLC
profiles, which can be used to predict processing quality, also showed gradients
across the grain.
The pattern of distribution of starch showed an opposite trend to that of
proteins, being higher in the central endosperm cells than in subaleurone cells.
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The amylose/amylopectin ratio also varied spatially in grain of some of the
cultivars.
Strong genotype effects were found for all parameters that were measured.
Nitrogen fertilisation was found to have a strong impact on the amount of
protein (both quantity and quality) and their distributions. Moreover, it also
influenced, albeit to a much smaller extent, the amount of starch.
The detailed information on protein and starch distribution within endosperm
and effects of genotype and nitrogen fertiliser from this study provided
knowledge that would lead to greater understanding of protein and starch
synthesis as well as nutrition transport within grain. It is also potentially
beneficial for improving milling technology and selecting breeding candidates for
different purposes
