Causes of bread staling

Causes of Bread Staling

Mwove, Johnson Kyalo,

M.Sc. Food Science

Egerton University

Dairy and Food Science and Technology Department

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Food Science Seminars 13th April 2014

INTRODUCTION

Bread staling is a complicated process that

involves loss of aroma, changes in mouth

feel, loss of crumb softness and development

of crumbliness.

It is a term which indicates decreasing

consumer acceptance of bakery products

caused by changes in crumb other than those

resulting from spoilage organisms

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INTRODUCTION

Bread staling is a complex phenomenon that

originates from multiple physico-chemical

events (amylopectin retrogradation, water loss

and redistribution and gluten-starch

interactions and gluten transformations) that

are not yet completely elucidated.

(Curti, et al, 2011)

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INTRODUCTION

It is usually characterized by

loss of aroma,

changes in mouth feel,

development of crumbliness.

toughening of the crust,

firming of the crumb,

loss of moisture and flavor,

loss in product freshness

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Theories explaining bread staling

The main causes of bread staling are thought

to be:

starch retrogradation

water migration and redistribution

Protein-starch interaction

Gluten transformations *

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Starch retrogradation

Retrogradation is a reaction that takes place in

gelatinized starch when the amylose and

amylopectin chains realign themselves causing

the dissolved starch difficult to re-dissolve.

Starch undergoes swelling or gelatinization

when heated in the presence of water

– Starch gelatinization

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Starch paste consists of amylose and

amylopectin. Amylose has greater tendencies

to gelatinize faster than amylopectin.

Amylose thus retrogrades faster.

When cooling begins, starch reorganizes itself

to achieve the crystalline structure it had

before.

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Due to this realignment, crumb firming

occurs.

When staling is measured as hardness

increase and increase in starch retrogradation,

it increases along the storage period.

(Barcenas and Rosell 2006)

Incorporation of water in the starch crystalline

structure occurs further reducing the moisture

content of the crumb.8

Water migration and Redistribution

The migration of water in cellular solid

foods during storage has been found to

cause loss of crispness.

Migration of water occurs within bread and

from bread to the environment causing

bread to firm.

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When bread is stored with crust;

Water migrates from crumb to the crust

The crumb firms

Loss of crispiness

The crumb moisture content and water

activity decreased

Decrease in freezable water

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When bread is stored without crust;

Moisture content remain relatively the same

No water migration occurs when crust is

absent

Less firming occurs

No change in total and freezable

water

(Baik & Chinachoti, 2000).11


Decrease in crumb moisture is caused by

Incorporation of water into the starch crystalline

structure

Loss of water to the surrounding environment

Moisture migration from crumb to crust reduces

the level of plasticizing water of the biopolymer

networks and contributes to crumb firmness at

longer storage times.

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Why the moisture migrates to the crust

from the crumb remains unexplained!

The crust undergoes retro gradation to a larger

extend than the crumb.

Increasing moisture content of bread does not

always result in softer breads (Piazza & Masi,

1995)

It is better to prevent bread staling by preventing

moisture loss from the bread than increasing the

moisture content of bread. 13

Protein-starch interaction

Bread firmness is thought to result from glucan chains

of partially leached amylose and amylopectin attached

to swollen starch granules forming hydrogen bonds with

other starch granules and, to a smaller extent, with

gluten fibrils.

The distribution of water is shifted from gluten to

starch, thereby changing the nature of the gluten

network during starch retro gradation.

(Gray & Bemiller, 2003)

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Gluten transformation

Gluten is the composite of a gliadin and a glutenin,

which is conjoined with starch in the endosperm of

various grass-related grains.

There is considerable uncertainty about the role of

protein in bread staling.

One of the main problems with gluten-free breads is

their texture and their rapid staling.

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Gluten transformation

High protein breads shows lower extent of retro

gradation and hence staling.

Waxy wheat flour blends have been also found with

the ability to retard staling of breads.

Protein is thought to retarded bread staling by diluting

starch and hence reducing starch retrogradation.

Addition of bacterial protease to sourdough has been

found to increase bread firmness and staling

indicating that proteins actually are important in

retarding bread staling.

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Prevention of staling

Enzymes – Heat stable Alpha Amylases

Shortenings

Emulsifiers- Surface active agents

Reheating - Temperature 70-80 Degrees C

Packaging

Soy addition

Malting and Fermentation

Incorporation of high fiber flour17

CONCLUSION

Minimal gelatinization takes place in the oven

and thus minimal retrogradation would be

expected to occur in bread.

Water moves from the crumb to the crust

when the crust is present and it does not move

at all when the crust is removed.

The effect of gluten in bread staling needs

further clarification.

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CONCLUSION

Proofing- the final dough rise contributes to the

structure of the crumb and therefore it has some

contribution on bread staling.

Staling of baked products is always unacceptable to

the consumer

It adds losses to the bakery since stale bread is not

fit for sale.

For this reason, a solution to the bread staling

problem is of urgent importance.

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Thanks for listening

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Causes of bread staling

Food

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