Causes of bread staling

Causes of bread staling

1. 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 13
th
April 2014

2. 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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3. 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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4. 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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5. 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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6. Starch retrogradation
Retrogradationis 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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7. Starch retrogradation
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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8. Starch retrogradation
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.
(Barcenasand Rosell2006)
Incorporation of water in the starch crystalline
structure occurs further reducing the moisture
content of the crumb.
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9. 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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10. Water migration and Redistribution
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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11. Water migrationand Redistribution
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).
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12. Water migrationand Redistribution
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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13. Water migrationand Redistribution
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.
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14. Protein-starch interaction
Bread firmness is thought to result from glucanchains
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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15. Gluten transformation
Gluten is the composite of a gliadinand 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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16. 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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17. 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 flour
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18. CONCLUSION
Minimal gelatinization takes place in the oven
and thus minimal retrogradationwould 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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19. 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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20. Thanks for listening
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