The Biochemical and Molecular Basis of Wheat Quality - Wheat Science and Trade - page 478

INTRODUCTION

21.1). Provision of these quality specifi cations
starts with the breeder, who is responsible for
creating the genotype (cultivar), based ultimately
on feedback from the customer. The quality
potential “built in” by the breeder is, in turn,
modifi ed by growth and storage conditions (Fig.
21.1).
These quality specifi cations include pheno-
typic attributes such as dough quality, starch-
pasting properties, possible grain defects, and
enzymic activities. If these attributes can be
reduced to the biochemical and molecular levels,
the breeder's task is likely to be simplifi ed, because
inheritance is simpler for a specifi c target protein
than for a quantitative trait such as dough
quality.

Wheat fl our is uniquely suited to the production
of leavened bread, largely due to the viscoelastic
properties of the gluten proteins. Thus, the
protein content of wheat grain is a signifi cant
attribute in trade. Protein quality is also impor-
tant, but it is not so readily measured as is protein
quantity. Despite the importance of the protein
component, it is said that wheat fl our has just the
“right” types of starch, lipid, and pentosan to suit
it for breadmaking. It is thus appropriate to con-
sider the full range of grain components when
attempting to understand the biochemical basis of
wheat quality.
We also need to study the range of uses of
wheat; this range extends well beyond the narrow
concept of “a loaf of bread,” to include the great
diversity of wheat-based foods around the world,
as well as wheat's many industrial uses (Faridi
and Faubion 1995). Each of these uses has its own
unique set of grain- and fl our-quality specifi ca-
tions, which are ultimately determined by the
appropriate consumer, via the processor (Fig.

DIVERSITY OF WHEAT UTILIZATION

The range of uses of wheat — western
foods
In the western diet, pan bread is the most obvious
food product made from wheat, generally “bread

GENOME
Relevant genes

TRANSCRIPTOME → PROTEOME
mRNA of genes Polypeptides
↓
FUNCTIONAL
ENVIRONMENT PROTEINS
Climate, Nutrients ↓
Farm management
GRAIN
COMPOSITION
↓
PROCESSING
Functional
properties
↓
FOOD PRODUCTS
↓
Consumer
acceptance

Fig. 21.1 The pathway of
grain quality from breeder
(genome) and grain-grower
(environment) to the con-
sumer, via molecular aspects
of grain composition.