Packaging and bread staling

1.  Packaging
 Minimize the time between cooling &
packaging
 Bread should be cooled sufficiently before
packaging
 Wrapping has no direct effect on the chemical
staling but reduces the rate of crumb firming as
compared to unwrapped bread
 Permits the moisture in bread to equalize
between the crumb & crust
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2.  Objectives
Protect bread against possible contamination
Minimize moisture losses
Make the handling of product more easy
Make the product appealing for customers
Provide the customers information on
nutrition, ingredients and other labeling
information about product
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3.  Storage
 Prevent the bread from sunlight
 Store at room temperature rather than at
refrigeration temperatures
 Freezing of bread is the most effective way for
either inhibiting or retarding the bread staling
process
 Bread stored at -34.4 0C found to retain its
fresh flavor & aroma after 30 days & remained
in good condition & saleable up to 345 days
 Wrapped bread requires more time to be
freezed than unwrapped
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4.  Unwrapped products dry out excessively in
one or two weeks
 Prevent bread during freezing from extraneous
odors as it can readily take it up
 Avoid temperature fluctuations, it may
deteriorate quality
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5.  Bread staling
Progressive deterioration of bread quality
during storage by two ways:
 Series of slow chemical or physical changes
leading to crumb firming commonly known as
staling
 Loss of bread freshness due to microbial attack
 Higher the moisture content, the more
pronounced the changes
 Bread & cake stale quickly than cookies &
crackers due to more moisture
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6.  Important changes affecting quality of bread
during storage include:
 Crust staling
 Crumb staling
 Crust staling
 Less complex than crumb staling
 Changes are converse of those in the crumb
 Crust becomes soft & leathery
 Fresh flavor & aroma replaced by a faintly
bitter taste
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7.  Causes
 Fresh crust is hygroscopic
 Absorbs moisture from air & interior crumb
 After four days storage under conditions of no
moisture loss, moisture contents change from
12%(m.c after baking) to 28% with a
concomitant moisture loss from crumb
 Packaging the bread before adequate cooling
also promotes staling
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8.  Crumb Staling
 More complex, more important & less understood than crust
staling
 Firmness varies with position within loaf, with maximum in
central portion of crumb
 Changes in aroma & flavor
 Increase in crumb hardness & opacity
 Crumbliness & starch crystallization
 Decreased crumb absorptive capacity
 Increased β-Amylase susceptibility of starch & soluble starch
content
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Important changes by crumb staling include:

9.  Processes resulting in crumb firmness
include:
 Starch retrogradation
 Modification of gluten structure, producing
labile moisture
 Absorption of moisture by retrograding starch
 Partial redistribution of moisture & migration
from centre to outer regions
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10.  Flavor Changes
 Changes in flavor during staling are
qualitative & quantitative & may be temporary
or permanent
 The most noticeable changes take place
between 48-72 hours of storage
 Intensity of many flavors fade with time &
surviving flavors become more discernible
 Oxidation of aldehydes causes flavor changes
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11.  Factors Affecting Crumb Staling
Principle factors responsible for staling
 As starch swells, part of linear fraction dissolves &
diffuses into surrounding aqueous medium
 On cooling this solution sets into an insoluble gel
structure
 Portion of amylopectin & amylose chains project
from swollen starch grains & associate with each other
& other carbohydrate chains in aqueous medium
protruding from nearby granules
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 Role of Starch

12.  Gradual changes in the starch components
from amorphous to crystalline forms is
important to the staling process
 Spontaneous aggregation of amylopectin
molecules may be responsible for bread firming
 Heating stale bread at above 50 0C restores its
original freshness, as retrograded amylose
cannot melt at this temperature so amylopectin
is considered responsible for the staling
 Most of scientists consider a relationship
between amylopectin retrogradation & staling
 Retrogradation of amylopectin may not be the
only reason for bread firming
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13.  Due to its rapid rate of retrogradation amylose is
considered to be responsible for setting of initial
crumb structure
 Amount of amylopectin in fresh bread, found to be
more than amylose that indicates the leaching of some
amylose from granule into surrounding medium
 As bread cooled to room temperature, amylose
fraction specially the leached one, becomes insoluble
by retrogradation, so little role of amylose considered
in staling
 Amylose may be responsible for the staling, on the
first day only
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 Role of amylopectin

14.  Starch grains in the baked bread are still
largely intact, although deformed but not
completely disengaged
 Molecular chains may reassociate as in native
granule, this recrystallization may be important
in staling
 Bread staling can not be attributed entirely to
the starch retrogradation
 Temperature & retrogradation may be
responsible for staling & refreshing of bread
along with other factors
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15. Role of flour proteins
 Three concepts required for firming:
 Reduce firming rate during staling has no
effect
 Generally believed that starch-gluten
interactions are somehow involved in the
firming process
 Starch retrogradation alone may be sufficient
to effect bread staling (Martin & others 1991)
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16.  Increasing protein level may decrease firming
rate as this may reduce association between
starch molecules
 Ratio of starch to protein in dough is important
in determining the rate of staling, some staling
will occur no matter how much protein is
added
 Rate of staling may be independent of protein
quality & the primary effect of protein in
reducing staling may be mere the dilution of
starch
 Several investigators conclude that staling is
not significantly correlated to flour protein type
or concentration
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17.  Qualitatively, starch-starch & starch-protein
interactions are of equal importance to staling
but quantitatively starch-starch interactions are
more important as flour contains more than
85% starch
 Bread firming may be a result of hydrogen
bonding between gelatinized starch granules &
gluten network
 When reheated, bread freshness is restored
because crosslinks between gluten & starch are
easily broken
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18.  Role of Pentosans
 Water insoluble pentosans
 Contradictory information is available
 No difference in staling rate of breads made with or
without tailings (starch fraction containing 9% water-
insoluble pentosans ) Bechtel & Meisner, 1954
 Their addition may result in considerable increase in
loaf volume & lowered staling (Kulp, 1968)
 Reduce bread quality, addition of pentosanase may
be a remedy (Krishnarau & Hoseney 1994)
 Variable results may be due to differences in type,
molecular weight and concentration of pentosans
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19.  Water soluble pentosans
 Positive effect on volume & retardation of
retrogradation
 Their effects depend upon differences in
baking properties of flours of different
cultivars, chemical composition & the way
pentosans were incorporated in dough
 Reduction in firmness may be due to higher
moisture content of the system
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20.  Pentosans & Starch Retrogradation
 Pentosan-gluten interactions may be
responsible for baking improvements
 Pentosans may inhibit retrogradation
 Arabinoxylan fortified breads exhibit greater
starch retrogradation due to higher moisture
contents
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21.  Role of native lipids
 Have effects on anti-firming action of
shortening
 Complexes formed between native lipids &
amylose within first two days of storage reduce
maximum amount of starch retrogradation
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22.  Conclusion
It is probable that several factors play a role in
bread firming process:
 Large volume of data that implicates amylopectin
retrogradation are considered as key factors
 The information that gluten is also involved cannot
be ignored
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23.  Antistaling Additives
 Enzymes
 α-amylase improves softness retention of
bread to an extent related to their heat stability
 Reduce both starch retrogradation & crumb
firming
 Antistaling effect is due to ability of producing
partially degraded amylopectin that is less
prone to crystallization
 Produce partially degraded amylose,
responsible for rapid formation of partially
crystalline polymer network in fresh bread that
resist later rearrangements
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24.  Mixture of pullulanase & α-amylase cause
bread to stale at faster rates but amylase alone
retards firming
 Starch hydrolysis products are involved in
staling inhibition but these must be either
maltotriose & maltotetrose or longer than those
present in traditional maltodextrin
preparations
 Other important enzymes used in the
retardation of staling include lipases,
lipoxygenases, hemicellulases, cellulases &
proteases
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25.  Surface Active Agents
 The most important include; Diacetyl tartaric
acids esters of monoglycerides (DTAEM),
lecithin, monoglycerides, polyoxyethylene
monostearate (POEMS), sodium stearoyl
lactylae (SSL), glycerol monostearate (GMS)
 Used to keep the crumb softer for longer
periods by retarding staling
 Mode of action is mainly due to their amylose-
surfactant, amylopectin-surfactant & protein-
surfactant interactions
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26.  Effective in retarding bread staling
 Antistaling action differs from monoglycerides
 Hydrocolloids/gums, damaged & modified
starches
 Have high water holding capacity
 Inhibit water movement in the bread & may
retard staling
 Increase bread volume & shelf life
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 Carbohydrate ingredients
 Shortening

27.  Summary
 Retrogradation of starch remains the most
widely accepted factor contributing to bread
staling
 While amylopectin retrogradation is believed
to play the major role, amylose now also
thought to be involved
 Moisture transfer among bread components
contribute to bread staling
 Gluten serves as moisture reservoir from
which water is transferred to retrograding
starch molecules
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28.  Both starch & gluten contribute to staling with the
process weighted towards starch retrogradation, since
there is much more starch than protein in bread
 Additives that seem to have the greatest effect in
reducing staling in bread are surfactants, α-amylases
& hydrocolloids including modified starch
 Polymer crystallization, specially of amylopectin is
involved in staling process
 Retrogradation involves incorporation of water
molecules into crystallites, reducing the water
associated with gluten & change the nature of gluten
network
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29.  Surfactants change physical & chemical nature
of components involved in forming
supermolecular structures, prevent associations
or less perfect associations are formed
 Hydrocolloids affect by retarding
redistribution of water
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30.  Microbial Spoilage
 Mold growth
 Mainly due to post processing contaminations
 Bread is free of molds & mold spores after
baking
 Becomes contaminated with mold spores from
atmosphere during cooling, slicing, packaging
& storage
 Dry ingredients specially flour is contaminated
with spores
 1 g of flour may contain 8000 mold spores
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31.  The production operations like weighing & sieving
may increase mould count in air
 Molds will not grow on bread with relative humidity
< 90%
 In humid conditions more growth if bread is wrapped
without adequate cooling
 Sliced & wrapped bread is more at risk
 Rate of spoilage depends upon recipe & processing
method
 Cultured breads like rye bread have longer shelf life
due to more acidity
 Breads from no-time doughs have shorter life due to
less alcohols content than fermented breads
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32.  Rhizopus nigricans is the common bread mold
 Storage temperature affects the type of mold
 Certain molds produce mycotoxins
 Exposure to toxins may result from eating
bread either containing mycotoxins or
containing mycotoxinogenic molds
 10% Aspergillus & penicillium are toxic to
mice
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33.  Bacterial Spoilage
 Rope is the problem caused by Bacillus subtilis
at relative humidities >90%
 Primary sources are air, raw material &
equipment
 Flour is the greatest source of organism among
ingredients
 The spores easily survive baking & germinate
within 36-48 hrs inside the loaf
 Bacterial amylase & protease degrade crumb,
causing discoloration & stickiness
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34.  Conditions favoring rope are
 Storage above 25 0C
 pH above 5
 Moist loaf
 High spore level
 Rope is rare due to addition of calcium
propionate & better sanitation conditions
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35.  Yeast Spoilage
 Main sources of contamination are dirty equipment &
infected high sugar foods
 Mainly two types of yeasts involved
 Fermentative yeast
 Sugars present in bread are fermented by these yeasts
 Spoilage manifested by alcoholic off-odor
 Saccharomyces cerevisae is important
 Filamentous yeasts
 Referred as chalky yeasts due to white, spreading
growth on the bread surface confused with mold
 Pichia burtonii is the most troublesome, growing fast
& resistant to preservatives & disinfectants
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36.  Control of microbial spoilage
 Preservatives
 The most commonly used preservative is
propionic acid & its salts
 Distorts pH equilibrium of microbes
 Mainly effective against bacteria & mold so
can be used in bread without disturbing
leavening activity of yeast
 Ethanol @0.5-3.5% of loaf weight extends shelf
life
 Gives same results if sprayed over bread
surface before packaging
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37.  Modified Atmosphere Packaging
 Storage of food in increased concentrations of CO2
 No need to be declared on label
 Increases shelf life without affecting taste, flavor &
aroma
 Retards mold growth when present in concentrations
>20%
 Shelf life increases with increase in concentrations
 Effect depends upon ERH
 Bakery products with ERH 85% or below, can obtain
400% increase in shelf life at 75% or above CO2
concentration
 60% CO2 with 40%N2 give best results
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38. Methods of wrapping the products under MAP
 Form fill sealing
 The air is replaced with continuous stream of gas
before sealing the package
 Speedy, versatile & can be adjusted to different
product sizes & wrapping materials
 Chances of gas leakage
 Vacuum packaging
 Air is removed creating vacuum followed by addition
of desired gas mixture
 Less flexible system & requires two steps to replace
air
 Limited use due to cost of gas, wrapping equipment
& laminated films used in process
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39.  Irradiations
 Ultraviolet irradiations
 Powerful antibacterial agent with the most
effective wavelength being 260nm
 Used to control mould spores on the surface of
bread
 Does not generate heat to damage wrapping
film or promote condensation problem
 Difficult to treat multi-surfaced product due to
poor penetration power
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40.  Microwave radiations
 Lie between infrared & radio frequency of
electromagnetic spectrum
 Heat rapidly & evenly without major
temperature gradients between surface &
interior of homogenous product
 Cause condensation problems that can
adversely affect quality
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41.  Infrared radiations
 Used to destroy mold spores by heating
surfaces to desired temperature of 75 0C
without affecting quality or appearance of
product
 Time required depends upon thickness of
packaging material, nature of the product &
distance between infrared injector & surface of
product
 Heats only the outer surface to minimize
condensation of moisture or air expansion
 Costly for multi-sided products that are
required to rotate between heaters or heated in
two separate ovens
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