Food Biochemistry and Food Processing

618 Part VI: Fermented Foods

decrease firming (retrogradation) upon storage since
these enzymes are not fully denatured during baking.

Proteases Proteinases and peptidases are found in
cereals, and their primary function is to make small
amino nitrogen compounds available for the devel-
oping seed embryo during germination, when the lev-
els of these enzymes also increase. However, whether
these enzymes have a role in bread baking is not cer-
tain. Peptidases may furnish the yeast with soluble
nitrogen during fermentation, and a proteinase in
wheat that is active at low pH may be important in
acidic fermentations such as sourdough bread.

Lipases Lipases are present in all grains, but oats
and pearl millet have a relatively high activity of
lipase compared with wheat or barley (Linko et al.
1997). In flour of the former grain types, hydrolyt-
ic rancidity of the grain lipids and added baking fat
may be a problem.

LIPIDS

Lipids are present in grains as a large number of dif-
ferent compounds, and they vary from species to
species and also within each cereal grain. Most lip-
ids are found within the germ. Wheat flour contains
about 2.5% lipids, of which about 1% are polar lip-
ids (tri- and diglycerides, free fatty acids, and sterol
esters) and 1.5% are nonpolar lipids (phospholipids
and galactosyl glycerides). During dough mixing,
much of the lipid forms hydrophobic bonds to the
gluten protein (Hoseney 1998).

BREAD

Many different types of bread are produced in the
world. Bread formulations and technologies differ
both within and between countries due to both tradi-
tional and technological factors including (1) which
cereals are traditionally grown in a country and their
suitability for bread baking, (2) the status of bread in
the traditional diet, (3) changes in lifestyle and liv-
ing standards, (4) globalization of eating habits, and
(5) economic possibilities for investing in new types
of bread-making equipment.
The basic production of most bread involves the
addition of water to wheat flour, yeast, and salt.
Other cereal flours may be blended into the mixture,

and other optional ingredients include sugar, fat,

malt flour, milk and milk products, emulsifiers, and

gluten (for further ingredients and their roles in

bread, see Table 27.1). The mixture is worked into

an elastic dough that is then leavened by the yeast to

a soft and spongy dough that retains its shape and

porosity when baked. An exception to this is the pro-

duction of bread containing 20–100% rye flour,

where the application of sourdough and low pH are

required.

BREADFORMULATION

The formulation of bread is determined by several

factors. In a simple bread, the baking properties of

the flour are of vital importance in determining the

characteristics of the loaf using a given technology.

In addition, the bread obtained from using poor

bread flour or suboptimum technology may be im-

proved by using certain additives (Table 27.1).

The major methods used to prepare bread are

summarized in Figure 27.2. In the straight dough

method, all the ingredients are added together at the

start of the process, which includes two fermenta-

tion steps and then two proofing steps. In the sponge

and dough method, only part of the dry ingredients

are added to the water, and this soft dough under-

goes a fermentation of about 5 hours before the re-

mainder of the ingredients are added and the dough

is kneaded to develop the structure. Although these

processes are time consuming, their advantages are

that they develop a good flavor in the bread and that

the timing and technology of the processes are less

critical (Hoseney 1998). Mechanical dough devel-

opment processes, such as the Chorleywood bread

process developed in the United Kingdom in the

1960s, radically cut down the total bread-making

time. The fermentation step is virtually eliminated,

and dough formation is achieved by intense mechan-

ical mixing and by various additives that hasten the

process (Kent 1983). The resulting loaf has a high

volume and a thin crust but lacks flavor and aroma.

The trend is now away from this kind of process due

to customer demand for more flavorful bread and

reduced use of additives.

THEDEVELOPMENT OFDOUGHSTRUCTURE

When wheat flour and water are mixed together in

an approximately 3:1 ratio and kneaded, a viscoelas-