Baking Fundamentals

7/28/2019 Baking Fundamentals

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Kneading ConferenceWest 2011 !

Baking Fundamentals - Core Concepts !

Lee Glass!


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Course overview !

! ! Fundamentals: !! ! Introduction !! ! Starch!! ! Proteins !! ! Yeast!! ! Salt!! ! Mixing!! ! Fermentation !! ! Baking!


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History !

! !Post-World War II !! !US: Prosperity !

! !

Levittown - a home for everybody!

! !More rural electrication: lots more things to do !! !Chevrolet - See the USA in your Chevrolet !! !Supermarkets replaced neighborhood stores !! !

Newer is better!


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Post-WW II Prosperity - US !

! ! Chemistry - cornerstone of prosperity !! ! Monsanto: Better living through chemistry !! ! Pittsburgh Paint & Glass: grape avoring !! ! Cereal chemists -- the biochemistry of grains !! ! Age of the atom -- plant research with radiation !! ! Food chemists - bringing it all home !

! ! Wonder Bread !! ! Holsum Bread !! ! Etc.!


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Post-WW II: Europe !

! !Food and money were scarce followingWW II (Rationing ended in England in

1952)!

! !Important that production minimize costsand maximize output !

! !Adoption of techniques being popularizedin the US!

! !Result: French Wonder Bread !


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Artisan Breads !

! !A tradition with some long-established bakeries: e.g. Boudin (since 1849, in SFO)!

! !

Created by others who sought to provideartisan products: e.g. Acme Bakery, bySteve Sullivan, in 1983; Artisan Bakers, byCraig Ponsford, in 1992 !

! !Now a major market: e.g. Essential,Macrina, Le Panzanella, Grand Central,and others, all in Seattle !


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Science in Breadmaking !

! ! Chorleywood Process: It s all science!! ! Flour to packaged loaf in ~ 3.5 hours !! ! Mixing measured by energy input in kWh, not dough

characteristics !! ! Negative pressure proong !! ! Decreased partial pressure nitrogen compared to air !

! ! Artisan bread: little emphasis on science !! ! Most texts emphasize how to , not why !! ! No standardized national basic instruction for bakers !


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Questions !

! !Can we as artisan bakers use knowledgeof the science underlying breadmaking to: !

! !Help our breads develop

!! !Maximum avor !! !The desired crumb structure and consistency !! !The crust we are seeking !! !

The color we want our loaves to have?!

! !Help manage our doughs? !


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Goals of this segment !

! ! Explore basic science knowledge related to !! ! Flour!! ! Yeast!! ! Salt!! ! Water !! ! Mixing!! ! Fermentation !! ! Baking!

! ! Explore practical correlates of that knowledge !


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Goals of key players !

! !Goal of wheat: make more wheat !! !Goal of yeast: make more yeast !! !Goal of lactobacilli: make more lactobacilli !! !Goal of baker: make bread !! !Key challenge for baker: orchestrate a

symphony for discordant instruments !


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Flour !

! ! Starch!! ! Long chains ( polymers ) of glucose molecules !

! ! Amylose = straight chains !! ! About 25% of wheat starch !

! ! Amylopectin = branched chains !! ! 1 branch for about each 30 or more glucose molecules !! ! About 75% of wheat starch !

! ! Starch granules are compact clusters of amylose andamylopectin !

! ! Starch granules absorb little water at room temp !! ! With heat, starch granules can bind large quantities of

water !


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Starch !

! !Some roles of starch in bread making !! !Absorbs huge amounts of water during

baking !! !Stabilizes the crumb !! !Its ultimate breakdown product (glucose) has

a major effect on crust color and avor !! !Its ultimate breakdown product (glucose)

feeds yeast (and bacteria, if any) !


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Starch !

! !Wheat consists of ~60% starch !! !Role of starch for wheat: feed developing

seedling. !! !Seedlings, yeast & lactobacilli cannot eat

starch !! !

Starch must be converted to smallercomponents to be a useful energy source !! !Conversion is facilitated by enzymes !


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Starch - Interaction with

proteins !! !Enzymes are proteins that facilitate

chemical reactions, without themselves

changing!

! !Enzymes work within narrowtemperature and pH ranges !

! !Enzymes are extraordinarily specic inwhat they do !


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Proteins !! !Amylase !

! !Beta: normally present in substantial amountsthe wheat kernel !

! !Alpha: presence depends upon growingconditions, weather near time of harvest, andother factors. !

! !

Barley is sprouted, dried, powdered, and added atthe mill if necessary in order to have appropriatelevels of alpha-amylase in the milled product. !


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Proteins !! !Amylase - two major forms, with some

variation. !! !Alpha amylase: !

! !Can cut straight chains almost anywhere !! !Cannot cut branch points !

! !Beta amylase:!! !Starts at one end of a chain, and chops off 2 links at

a time. !! !Can cut at branch points. !

!


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Starch - Amylase !

! !Temperature data for wheat amylases: !! !Alpha-amylase !

! !Optimum range: 60 C to 70 C !! !Thermal inactivation: 70 C to 85 C !

! !Beta-amylase !! !Optimum range: ~50 C !! !Thermal inactivation: 55 C to 75 C !

! !Fungal amylase are less heat stable !


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Proteins !! !Amylase activity !

! !Measured by falling number !! !Falling number = number of seconds for a weight

to settle through a hot, gelatinized starch mixture !! !Rationale: as alpha-amylase cuts the starch chains,

starch s ability to continue to hold waterdecreases, viscosity decreases, and the weight falls

faster. !! !The falling time reects, indirectly, the amount of

amylase activity. !


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Proteins !! !Products of alpha- and beta-amylase on

starch:!!

!Alpha: principally => !! !1 sugar (monosaccharide) = glucose !! !2 linked glucose molecules = maltose !! !Longer chains !

! !Beta: principally => !! !2 linked glucose molecules = maltose !


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Starch - Granules !

! !Granules: !! !Tight, compact bundles of amylose and

amylopectin !! !Compactness resists effects of amylases !


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Starch - Damaged !

! ! Damaged starch granules: !! ! Present at about 5% to 10% of the starch !! ! Have very different qualities than native starch !! ! Can absorb water at room temperature !! ! Easily attacked by amylase !! ! Absorb their own weight in water !! ! If present at >10%, dough will be sticky !! ! The higher the percentage of damaged starch, the

softer the crumb !! ! At high percentages, may cause keyholing !


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Proteins !

! !Proteins are chains !! !Each link in the chain is an amino acid !

! !The order of the amino acid sequences,and the characteristics of the amino acids,cause the chains to twist into complexshapes. !

! !The shapes are related to what theproteins do (form relates to function) !


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Proteins !

! !Water-insoluble !! !Most important for bakers: gluten proteins: !

! !Gliadins -- low molecular weight storage proteins !! !Glutenins -- hi molecular weight storage proteins !! !Note: storage proteins are found principally in the

endosperm !


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Proteins !! !Gliadins !

! !Most extensively studied (to nd markersthat might correlate with wheat quality) !

! !Hundreds of different, distinguishablegliadin components !

! !Gliadins are compact, tightly foldedmolecules !

! !Relatively stable to temperature challenges !! !Contain the portion of gluten that causes

celiac disease (an immune reaction thatdamages the small intestine, causingmalabsorption problems) !


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Proteins !

! !Glutenins !! !Made up of a series of protein subunits that

are cross-linked in a way that produces a broad spectrum of sizes !

! !Huge molecules, compared to the gliadins !! !How these molecules are cross-linked is not

exactly clear.!


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Proteins !

! !Gluten structure !! !Clear underlying science (disulde bonds, etc.) !! !

Considerable controversy remains!

! !Possible:!! !Glutenin units link together !! !Gliadin units, singularly or as a polymer, link to

adjacent glutenin units!

! !Result: A three-dimensional protein fabric that hasmulti-directional extensibility !


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Proteins !

! !Gluten correlates of baking quality of our: !

! !

1. The gluten resists breakdown duringmixing !! !2. The gluten aggregates quickly during rest

and during stretch-and-folds !


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Proteins !

! !Flour protein is often expressed as asimple percent: e.g. 11.5% !

! !A percent number tells nothing about

!! !The nature of the protein !! !The quality of the protein !! !The characteristics of the dough that might be

made with the our !


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Proteins !

! !Classication - based on solubility !! !About 20% of the proteins are soluble in water !! !

The remaining 80% are not. It is in this 80%that the gluten-forming proteins can be found !! !Note: It is because these proteins do not

dissolve in water, and because bread is made

with water, that gluten forms. Were breadmade with acid, in which the proteins can bedissolved, gluten would not form. !


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Proteins !

! ! Water-soluble proteins !! ! Include physiologically active proteins: !

! ! Enzymes, e.g. !! ! Amylases !! ! Maltase !

! ! Albumins !! ! Globulins !

! ! Note: physiologically active proteins are foundprincipally in the aleurone layer, and in the germ !

! ! The fraction of total wheat protein that isphysiologically active depends on factors such asclimate, nitrogen availability, season during whichwheat grew, etc. !


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Proteins !

! !Distribution of proteins !! !Note that the distribution of proteins varies

from one part of the kernel to another. (Seeabove.)!

! !Implication: the portions of the wheat kernel blended by the miller to make a given our maytell more about the our s protein than may astated percent: !

! ! E.g. absent treatment by the miller, a patent our mayhave little enzymatic activity compared to a whole grainour from the same shipment of wheat kernels. !


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Yeast !

! !Saccharomyces cerevisiae !! !Single cell organism that can live with or

without oxygen!

! !With oxygen: glucose => CO 2 + energy !! !With oxygen: reproduce several times an hour !! !Without oxygen: glucose => CO 2 + ethanol! !Without oxygen: no reproduction


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Salt !

! !Salt has several actions: !! !Works as an anti-oxidant - Calvel

recommends its addition at the beginning of mixing !

! !Salt increases cohesiveness of dough duringmixing. (Without salt, dough stays slack.) !

! !Salt decreases fermentation (2% salt reduces

fermentation by 20%; 4% => 70% reduction) !! !Salt makes a benecial contribution to taste !


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Mixing !

! !Mixing - Overview: !! !Homogenizes the ingredients !

! !Disperses dry ingredients !! !Equalizes absorption of liquids !

! !Entraps air in the developing dough !! !Exposes dough components to oxidation !

!

!Enhances gluten development !! !May oxidize avor elements and decrease avor !


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Mixing !

! !Homogeneous mass: !! !Initially, not homogeneous !

! !Water absorption is uneven - rst particles to become wet get more water than later particles !

! ! Becomes uniform by end of mixing !! !Salt and sugars dissolve !

! ! Both may affect yeast activity !

! !Fats spread !! ! Affect gluten development !! ! Timing of fat addition may be important !


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Mixing !

! ! Entraps air in dough !! ! Gas nuclei -- a critically important concept !! ! Bubbles: Pressure resisting expansion = surface tension X 2

divided by bubble radius !! ! Mixing atmosphere: in craft bakeries, O 2 and N 2

! ! O2 is consumed immediately! ! N2 is poorly soluble, and stays in nuclei! ! CO 2 diffuses into nuclei

! ! Size of nuclei: depends upon atmosphere, mixer speed,shear forces !


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Mixing !

! !Exposes dough components to oxygen !! !Enhances gluten development !

! !Oxygen changes weak SH bonds to strong SS bonds !! !Dough strengthener: L-Ascorbic acid (vitamin C) !

! ! Ironically, not an oxidizing agent! !! ! It must rst be oxidized (to dehydroascorbic acid) !! ! All vitamin C is volatilized during baking !

! !Oxidizes avor elements !! !Carotenoid pigments => decreased avor !


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Mixing !! !Mixing intensity - !

! !Dough properties: water absorption - absorptionincreases with mixing intensity !

! !Dough texture: shear & elongation forcesdistribute and resize gas nuclei !! !Degree of mixing - !

! !Stage 1: end of homogenization - short dough !! !Stage 2: middle of mixing - coherence increases !! !Stage 3: strong coherence - window possible !! !Stage 4: sticky, extensible, soft - overmixing !


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Mixing !! ! Inuence of mixing on nal product !

! ! Coherence increases with mixing !! ! Result:!

! ! Crumb softness and resiliency increases !! ! Crust toughens !

! ! Inuence of temperature !! ! Affects fermentation (10% change / 1C) !! ! Note: 8g ice/kg dough => temp drops 1C !! ! Affects gluten development - increased speed of

development with increased temperature !! ! May affect moisture on surface of dough !


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Fermentation !

! !Process of fermentation: !! !Begins as soon as yeast cells are hydrated !! !Begins aerobically, as yeast respire oxygen

that is entrapped in the dough !! !Aerobic metabolism ends almost immediately

after mixing ends; oxygen is rapidlyexhausted from the gas nuclei !

! !From that point, reproduction ceases !


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Fermentation - no oxygen !! ! Formula: !

! ! One molecule of glucose => !! ! 2 molecules of ethanol (ethyl alcohol) !! ! 2 molecules of CO2

! ! Fate of products: !! ! Ethanol: enters liquid matrix, may combine with other

elements to produce flavor compounds! ! CO2:

! ! dissolves in water ! ! Diffuses into entrapped gas nuclei (now depleted of oxygen,

and containing only nitrogen from the atmosphere)


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Fermentation !! !Bulk fermentation !

! !Purpose: Continue dough development !! !Mechanism: biaxial stretching due to gas

development => toughening of the dough !

! !Stretch & Fold / Punch down !! !Purpose: Increase gluten strength !

! !Mechanism: increase protein cross-linking !

! !Final Proof !! !Purpose: Increase specic volume !

! !Mechanism: gas production !


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Fermentation !

! !Bulk fermentation !! !Begins with production of CO 2 from respiration !! !

CO2 is in a liquid phase in the space between gasnuclei!! !Concentration increases during rst ~30 minutes !

! !CO2 is in a gas phase within the gas nuclei !! !

Commences almost immediately!

! !Remains proportional to liquid-phase CO 2! !Force resisting gas cell expansion: surface

tension, not dough viscosity !


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Fermentation !

! !Gas Cells!! !Very stable: walls strengthen with stretching !! !Crumb: virtually no loss of CO

2from

membrane rupture, etc. !! !Surface: CO2 diffuses from dough into

atmosphere !! !

This accounts for crust structure!

! !If proofed in CO 2-rich atmosphere, crust is blistered and torn !


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Fermentation !

! !Change in pH !! !Multiple acids are produced, including: !

! !Carbonic acid -- in all fermenting doughs; fromCO2 and water !

! !Acetic acid -- sourdough !! !Lactic acid -- sourdough !

! !Acids are buffered by wheat proteins !! !pH yeast dough: 5.4 -- 5.7 !! !pH sourdough: 4.0 -- 4.5 !


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Fermentation !! !Temperature changes during fermentation !

! !Heat is produced !! !12g sugar / kg dough => ~2.8C /kg dough !

! !Condensation !! !1g moisture /kg dough => 1C temperature increase !

! !Evaporation !! !1g moisture /kg dough => 1C temperature decrease !

! !Air temperature !! !Heat capacity of air is 1.2 kJ/m 3*C!! !Specic heat of dough is 2.7kJ/kg*C !! !Result: air temp plays minor role in dough temp !


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Baking !

! !Baking produces massive physical changes !! !Dough (liquid) => crumb (solid) !! !Dough (foam) => crumb (sponge) !! !Dough (.8 liters/kg) => bread (up to 5 liters/kg) !

! !Baking produces massive chemical changes !! !Proteins give up water !! !Starch granules become hydrated !! !Maillard reaction occurs in the crust !


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Baking !

! !Heat transfer !! !Radiation = transfer of heat by

electromagnetic waves from a source of heat !! !Convection = transfer of heat by movement of

a uid away from a source of heat !! !Conduction = transfer of heat by molecular

agitation with the object, without overallmovement of the object itself !! !Condensation/Evaporation: heat transfer as a

result of phase change !


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Baking !

! !Radiation !! !Heat radiates from oven walls/deck/roof !

! !Electromagnetic radiation (between radio wavesand visible light) !

! !Short- and Medium wave infrared wavelengths !! !These waves do not bend !! !Result: color differences may occur between top

and sides of the bread !! !Penetration: maximum = < 1/4 (~4 mm, max) !


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Baking !! !Convection !

! !Cold object (dough) in oven => movement of air over the object and downward !

!

!Air movement causes heating by convection !! !Without a fan, convection is minimal !! !At 1 m/s airow, convection is about 1/3

total heat transfer !! !To prevent excessive crust browning from

forced convection, must lower oventemperature 20C -- 30C !


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Baking !

! !Condensation !! !With steam injection: !

! !Condensation on dough with steam injection =>surface temperature of 80 C, instantaneously !

! ! Gelatinizes starches, dissolves sugars !

! !Within dough: !! !Moisture evaporates from warmer side of gas cell,

travels across cell, and condenses on other side. !! !Moisture moves towards center of dough !! !The higher the specic volume of the dough, the

greater the contribution of evaporation/condensation !


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Baking !! !Effect of heat!

! !Initial increase in cell activity: initial increasedrate of CO 2 and ethanol production !

! !When temp >40C, CO 2 production declines !! !Increased rate of extra-cellular activity !

! !E.g. amylase !! !Proteins swollen with water, expel the water !! !Heat, in the presence of water, overcomes the

binding of one starch chain to the next in thegranules !


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Baking !! !Effect of heat!

! !At about 150 F, starch begins to hydrate !! !Separation of hydrated starch chains leaves

them subject to attack by amylases !! !Amylase in wheat our is active to about 167 F;

higher still in rye !! !Sugar results from the increased action of

amylase !! !Yeast cells have died from heat, so the sugar is

not metabolized !! !The resulting sugar softens and smooths the

crumb !


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Baking !

! !Crust color is affected by crust composition: !! !Short fermentation => reddish, not golden-brown !! !Low protein => pale, not golden brown !! !Low sugar => light colored crust !! !Skinned dough => faint crust color !

! !Moisture is necessary in rst ve or more minutes for

Maillard reaction!


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Staling !

! !Potential factors that have been examined: !! !Amylopectin retrogradation, amylose, our

protein, water-insoluble pentosans; water-

soluble pentosans, interaction of pentosanswith proteins, pentosans and starchretrogradation, native lipids, storagetemperature, moisture migration, crumb-crustmoisture redistribution, moistureredistribution among other components,processing factors !


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Staling !! !What can be said at this point: !

! !Complex phenomenon !! !Multiple mechanisms !

! !Polymer crystallization with !! ! Primary cause: Retrogradation (recrystallization) of

amylopectin, associated with !! ! Water distribution shifts, changing the nature of the

gluten network. !

!


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Cooling !! !Temperatures: !

! !At oven removal: Crust 180 C; crumb 100 C !! !After a few minutes: Crust and crumb 100 C !! !

Thereafter, crust temp < crumb temp!

! !Moisture from crumb evaporates; condenses in crust !! !Evaporating moisture in crumb lowers pressure !! !Atmospheric air enters crumb to raise pressure !

! !Note that forced convection cooling will allowmore water retention in the crumb than freeconvection cooling, because of the difference inevaporation rates !

Baking Fundamentals

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