Food Chemistry

716 15 Cereals and Cereal Products

15.4.1.3 Storage

Rye flour acquires optimal baking properties after
1–2 weeks of storage after milling. Wheat flour
requires 3–4 weeks. This storage period is the
flour “maturation time”. In wheat the time is nee-
ded for oxidative processes to occur and thus pro-
vide a stronger (shorter) gluten. In this time, the
concentrations of endogenous glutathione (GSH,
GSSG), which reduces the stability of gluten in
dough making (cf. 15.2.3), and PSSG decrease,
the rate depending on the wheat cultivar.

Flour with a moisture content of<12% may be
stored at 20◦C and a relative humidity of<70%
for more than 6 months without significant
change in baking quality.
Flour fumigation with Cl 2 ,ClO 2 ,NOCl,N 2 O 4
or NO, or treatment with dibenzoyl or acetone
peroxide results in carotenoid destruction. The
flour becomes bleached. Other reactions, not yet
elucidated, are involved with Cl 2 ,NOCl,ClO 2
and acetone peroxide treatment since they
provide simultaneous improvement in baking
quality of flours which have weak gluten.

15.4.1.4 Influence of Additives/Minor
Ingredients on Baking Properties
of Wheat Flour

The baking properties of wheat flours differ
widely (cf. Table 15.41). In small traditional
plants, a baker can use his experience to compen-
sate for changes in the quality of raw materials:
flexibility in formulations, dough handling and
baking – all these parameters can be adjusted in
order to obtain the desired end-product.
In a large-scale automated bakery, economic pro-
duction demands uniform raw materials with uni-
form properties. Additives are used when neces-
sary to adjust the flour characteristics to match
the baking process (for instance, shortened dough
handling time with low energy input). Additives
are also used to ensure that the end-product meets
existing standards. Incorporation of ascorbic acid,
alkali bromates or enzyme-active soy flour im-
proves the quality of weak gluten flour – e. g., in
bread or bun baking. In these cases the dough be-
comes drier and there are increases in dough re-
sistance to extension, mixing tolerance and fer-
mentation stability. In addition, baking volume

will increase and the crumb structure will im-

prove. Ascorbic acid and lipoxygenase require

oxygen for their actions; hence their beneficial

role is very dependent on the intensity of dough

mixing, which traps oxygen from the air.

In contrast, opposite effects may be observed by

adding cysteine or proteinases, the result being

gluten softening. Biscuits are made from such

mellowed, softened doughs, which are made with

little energy input. Additives which affect the

rheological quality of the dough and/or the

quality of baked products include emulsifiers,

shortenings, salt, milk, soy flour,α-amylase and

proteinase preparations and starch syrups.

15.4.1.4.1 Ascorbic Acid

The improver effect of ascorbic acid (Asc)

was recognized byJorgensenas early as 1935.

He found that small amounts (2–10 g Asc per

100 kg flour) caused an improvement in flour.

The dough becomes stronger (Fig. 15.31)

and drier and the bread volume increases in

most cases. The oxidation product of Asc,

dehydroascorbic acid (DHAsc) is also effective

(Table 15.42), but its use would be uneconomical.

In the example in Fig. 15.31, the addition of

40 mg/kg of Asc has a greater strengthening

effect on dough than 20 mg/kg. A further in-

crease in Asc to 80 or even 160 mg/kg no longer

increases the effect. But in comparison with

Fig. 15.31.Rheological properties of wheat dough as

a function of different concentrations of addedL-threo-

ascorbic acid (Asc) (according toKieffer, unpublished).

Tensile tests with dough made of 10 g of flour of the

variety Flair. Addition of Asc (mg/kg): 20◦–◦), 40 (•–

• ), 80 and 120( – ), 160(Δ–Δ). Control without ad-
  ditive: —