Food Biochemistry and Food Processing

620 Part VI: Fermented Foods

Another important part of the dough formation is
the incorporation of air, in particular nitrogen. This
forms insoluble bubbles in the dough that become
weak points where carbon dioxide collects during
the subsequent fermentation step. In the Chorley-
wood bread process, the dough is mixed under par-
tial vacuum so that the incorporated bubbles expand
and are then split into many small ones as mixing
continues, thus giving a fine-pored loaf crumb after
baking.

DOUGHFERMENTATION

During the fermentation step, several processes hap-
pen simultaneously, and in order to produce a bread
of the required quality characteristics, each of these
processes must be optimized to that end.
Yeasts have been used to leaven bread for thou-
sands of years, but only in comparatively recent
times have pure cultures of the yeast Saccharomyces
(S.) cerevisiaebeen added to the bread dough as a

leavening agent. The commercial production of bak-

er’s yeast follows procedures similar to those used in

the production of brewing, wine-making, and distill-

ing strains of this same species. Indeed, the baking

industry was originally supplied with yeast waste from

the brewing industry until about 1860 (Ponte and Tsen

1987). However, commercial production of yeast bio-

mass specifically for the baking industry developed

alongside an increasingly expanding manufacture of

bread in commercial bakeries and the development of

the technology that provided the great volumes

required by the industry.

Commercial Production of Baker’s Yeast

Saccharomyces cerevisiaewas originally produced

commercially using grain mash as a growth sub-

strate, but for economic reasons, it is now grown on

sucrose-rich molasses, a by-product from the sugar

cane or sugar beet refining industry. Nitrogen, phos-

phorous, and essential mineral ions such as magne-

Figure 27.2.Bread-processing methods. (Adapted from Hoseney 1994.)