Food Biochemistry and Food Processing

25 Rye Constituents and Their Impact on Rye Processing 585

noxylans may be positive due to the capacity of the
latter to gel and form a polysaccharide network in
the dough, thereby increasing water absorption, gas
retention, bread volume, and shelf life.

Proteins Proteins are only of secondary impor-
tance for rye bread-making quality because of their
inability to form a gluten network (Gellrich et al.
2003, 2004b; Kipp et al. 1996; Köhler and Wieser
2000). However, they should not be neglected, as
they seem to be important at the dough-mixing step,
at least for certain cultivars (Parkkonen et al. 1994).
Indeed, although rye proteins do not form a regular
gluten network, they have some ability to aggregate
(Field et al. 1983) and are surface active (Wan-
nerberger et al. 1997).

Sensory Properties of Rye Bread

Rye bread has a typical strong and slightly bitter fla-
vor. The most dominant sensory attribute of rye
bread is its rye-like flavor, but perceptions of sour-
ness and saltiness are also substantially associated
with rye bread (Heiniö et al. 1997). The aroma
results from a mixture of many different volatile
compounds formed by enzymic reactions during
fermentation and thermal reactions during baking
(Heiniö et al. 2003a, 2003b; Kirchhoff and Schie-
berle 2001). Besides the generation of aromas dur-
ing these steps, the flour itself is an important source
of dough aroma (Kirchhoff and Schieberle 2002).
The specific rye-like flavor can be slightly modified
to have a milder taste, without decreasing the high
dietary fiber content and other positive health effects
of rye, for example, by using the processing tech-
niques of sourdough fermentation, germination prior
to use, and extrusion cooking (Heiniö et al. 2003a),
or by milling fractionation (Heiniö et al. 2003b).

RYE INOTHERFOODPRODUCTS

In addition to bread, many other food products such
as ginger cake, porridge, pastries, breakfeast cereals,
and pasta products are based on rye (Kujala 2004,
Poutanen 1997). Rye can also be fermented to pro-
duce alcoholic beverages (Seibel and Weipert 2001a).

RYE INFEED

Although the majority of rye is fed to animals, rye is
considered to be of inferior quality to other feed

grains. The soluble, highly viscous rye arabinoxy-

lans cause reductions in both the rate of digestion

and the retention of nutrients in the gastrointestinal

tract (Boros et al. 2002, Fengler and Marquardt

1988b). Therefore, rye is generally used in small

proportions in mixtures with other grains. The use of

enzymes (Boros and Bedford 1999, Boros et al.

2002, He et al. 2003, Lazaro et al. 2003), however,

has recently substantially increased the proportion

of rye included in animal feed.

RYEFRACTIONATION

Wheat is an important raw material in the industrial

separation of gluten and starch because of the abun-

dant applications for gluten and starch in both the

food and nonfood sectors. Rye would be an interest-

ing alternative raw material because of the specific

properties of the rye constituents. However, in spite

of the development of some methods on the labora-

tory scale to separate starch from the arabinoxylans

and proteins in rye (Schierbaum et al. 1991), no

such industrial process exists for rye, presumably

because of its relatively high content of arabinoxy-

lans with high water-holding capacity and the inabil-

ity of the rye proteins to form gluten.

RYE ININDUSTRIALUSES

Rye and rye products are also used in industrial

applications such as production of adhesives and

glue, film coating, sludge and oil-well drilling mate-

rials, and textiles and paper (Seibel and Weipert

2001b).

RYE AND NUTRITION

Rye products, especially when they contain whole

meal rye flour, provide considerable levels of dietary

fiber, vitamins, minerals, and phytoestrogens, all of

which are considered to have positive health effects

(Poutanen 1997). High rye consumption leads to

positive effects on digestion and decreased risk of

heart disease, hypercholesterolemia, obesity, and

non-inulin-dependent diabetes (Hallmans et al. 2003,

Smith et al. 2003). It probably also protects against

some hormone-dependent cancer types (Hallmans et

al. 2003, Smith et al. 2003). Liukkonen et al. (2003)

showed that many of the bioactive compounds in

whole meal rye are stable during processing and that