Staling of bread

Rather than an overt series of flavour changes (cf. e.g. beer), the staling of bread primarily represents a loss of water. As a consequence, the crumb loses its softness and ability to swell, becoming unelastic, dry and crumbly. Some stale aromas do develop. The physical changes are due to changes in the starch polysaccharides. During baking, amylose diffuses out of granules and, when

Table 12.3 Analytical composition of breads.

Whole wheat bread

Rye bread

Moisture (%)

40

41

Protein (%)

7.5

7.0

Carbohydrate (%)

49

49

Fat (%)

1.5

1.4

Calories (kcal per 100 g)

240

237

Vitamins (% daily need)

A

20

E

134

B1

38

28

B2

25

23

Niacin

80

42

B6

60

Folic acid

14

Pantothenic acid

31

Minerals (% daily need)

Calcium 10-20 Copper 50 Iron 50

Magnesium 70-90 Manganese 30

Phosphorus 70-80

Potassium 60-70

Minerals (% daily need)

Calcium 10-20 Copper 50 Iron 50

Magnesium 70-90 Manganese 30

Phosphorus 70-80

Potassium 60-70

Data from Spicher & Brummer (1995).

bread cools, this forms a gel that embeds starch granules. Firmness in the crumb is due to heat-reversible association of the side chains of amylopectin within the starch and its retrogradation. Protein and pentosan also seem to be important. Ageing can be minimised by storage at elevated temperatures (45-60°C) or by freezing.

Preservatives such as propionates may be employed to protect against infection with organisms such as Bacillus mesentericus (which causes 'rope').

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