bio 9b: biology and chemistry of cooking winter 2006 lectures 15: doughs and batters i

Bio 9B: Biology and Chemistry of Cooking

Winter 2006

Lectures 15:

Doughs and Batters I

Copyright © 2006 Dr. Salme Taagepera, All rights reserved.

Doughs and Batters: Breads and Cakes

“Doughs”– Contain more flour than water– Stiff and pliable– All water bound up in starch and gluten

“Batters”– Contain more water than flour– Pourable– Much of the water is free liquid


DOUGHS AND BATTERS I & II:"All you knead to know about bread"

I. Raised breads dependent on unique characteristics of wheat flour

II. Gluten development

III. Leavening involves production of CO2 gas

IV. Additional ingredients in doughs

V. Preparing the dough

VI. Other dough products

VII. Batters

Lec

ture

15


Doughs and Batters

I. Raised breads dependent on unique

characteristics of wheat flour

A. Types of wheat flours: hard v. soft

B. Wheat flour components

-major components:

= gluten proteins (glutenin and gliaden), starch

-minor components:

= lipids, carbohydrates, enzymes


Flour is milled and sieved from wheat

• Most flours are refined– Oil-rich bran and germ are removed– Starch/protein-rich endosperm purified

• Two types of milling– Conventional (Theo kiểu truyền thống)– Stone-ground (Nghiền đá)


Components of flour

• Major components– Starch (70%)– Proteins (gluten proteins)

• Glutenin: elasticity (Đàn hồi) = resistance, “bounce-back” (Chịu tác động cơ học)

• Gliadin: plasticity (Mềm dẻo) = “stretchability” (Chịu kéo)

• Minor components– Lipids– Other carbohydrates– Enzymes


Levels gluten proteins determine characteristics of different flour types

Flour type

Wheat type

Protein content

Starch Content

Water absorption

Cake soft 7-8% 70-80% low

All Purpose

soft / hard

8.5-11.5% 70-80% middle

Bread hard 12-13% 70-80% high


Doughs and Batters

I. Raised breads dependent on unique characteristics of wheat flour A. Types of wheat flours: hard v. softB. Wheat flour components

-major components: gluten proteins (glutenin and gliaden), starch

-minor components: lipids, carbohydrates, enzymes

II. Gluten developmentA. Balance of plasticity (stretchability) and elasticity (resistance)B. Kneading: promotes unfolding (duỗi thẳng) and aligning (thẳng

hàng) of gluten moleculesC. Dough breakdown: excessive kneading results in loss of

crossbridges (Nhào quá nhiều sẽ dẫn đến các liên kết sẽ bị gãy vỡ _ 6 giai đoạn nhào)


Not just a single simple protein: made from a network of large interacting proteins

1. Glutenin – long coiled chain (các lk cuộn lại với nhau)– interact with each other in several ways (Tương tác với nhau bằng nhiều cách)– contributes elasticity “bounce-back” to dough(Tăng sự đàn hồi trong khối bột nhào)

2. Gliadin– compact and folded in on themselves (Gắn kết và cuộn lại trong nhau)– little interaction with each other– contributes plasticity “stretchiness” to dough (Tăng sự mềm dẽo, kéo dãn trong khối bột nhào)

gliadin

gluteninC-SHHS-C

H-O


Demonstration of plasticity Demonstration elasticity

gluteninC-SHHS-C

H-O

gliadin

http://www.fao.org/docrep/V5380E/V5380E0O.GIF


Gluten Development

C-S-S-C

C-S-S-C C-S-S-C

C-S-S-C

HO N

HNH

HO

cccc

cccc

cccc

glutenin

C-SHgliadin

HS-C

After adding water and kneading:

Hydrophobicinteractions

HydrogenbondingDisulfide bonds

Proteinsabsorb water

Gliadininterruptsglutenins

H-O


Components of flour

• Major components:

– Starch (70%)

– Proteins (gluten proteins)• Glutenin: elasticity = resistance, “bounce-back”• Gliadin: plasticity = “stretchability”


Components of flour: starch

• 70% of flour is starch

• Breaks up gluten network– tenderizes final product(Làm mềm sản phẩm cuối cùng)

• Starch granules swell (phồng) and set upon baking– provides the structural bulk of baked bread/cake(Tạo cấu trúc bánh)

• Some converted to sugars via enzymes– feeds the yeast


Components of flour


• Glutenin: elasticity = resistance, “bounce-back”

• Gliadin: plasticity = “stretchability”



Components of flour: lipids

Fats and oils:

• “shorten” glutenin network– Interacts (tương tác) with

glutenins, weakening glutenin intermolecular bonding

• lubricate gluten sheets– fat separates thin layers of dough– Allows for sliding (trượt) and

expansion (contributes to plasticity)


Components of flour


• Glutenin: elasticity = resistance, “bounce-back”

• Gliadin: plasticity = “stretchability”



Components of flour: enzymes

1. Malt enzymes– Break down starch into sugars– Normally activated in wheat when

embryo growth begins

2. Proteases– Slowly digest gluten proteins– Inhibit protease enzyme activity

with salt

http://www.mosquitonet.com/~stihlerunits/ScottsDen/Beer/Hmbrewing/acrospire.jpg

http://www.bioafrica.net/proteomics/PR-320x240-anim.gif


Doughs and Batters




A. Biological leavening: yeast (bread)

B. Chemical leavening: baking soda and powder (cakes)


Leavening: gas bubbles!(Làm nở bánh)

• Makes leavened products light and tender– 80% of bread’s volume

is empty space

• Divide gluten network into thin sheets

• Leavening functions by increasing size of pre-existing bubbles– Introduced through

mixing and kneading dough

Where do the gas bubbles come from?


Doughs and Batters







Biological leavening: yeast

• Yeast is a fungus that feeds on sugars

• The budding yeast (Saccharomyces cerevisiae), is the common yeast used in

= baking ("baker's yeast") = brewing ("brewer's yeast")

http://www.genomenewsnetwork.org/gnn_images/news_content/12_03/yeast/saccharomyces.jpg


Yeast metabolism is versatile!

1. Aerobic metabolism

2. Anaerobic metabolism

C6H12O6 CO2 + H2O + ATP

C6H12O6 C2H5OH + CO2

oxygen


Biological leavening: yeast

• Yeast is a fungus that feeds on sugars

• Yeast metabolism produces alcohol and the gas carbon dioxide – Cooking destroys the alcohol and kills the

yeast. – But the bubbles are left behind, and that's why

bread is soft


Doughs and Batters







Demo: Baking Soda Volcano

• Add baking soda and vinegar


Chemical Leavening: baking soda

Acid + Base ––––> CO2 + H2O + byproduct

– Bases:• Potash (potassium carbonate)

– Extracted from wood ash• Baking soda (sodium bicarbonate - NaHCO3)

– Acids:• Buttermilk, yogurt, brown sugar, vinegar,

chocolate, fruit juices, cream of tartar ( potassium hydrogen tartrate-tartaric acid)


Acid - Base reactionNaHCO3 + CH3COOH CO2 + H2O + Na+ + CH3COO-

base acid (ions in solution)

The acid and base neutralize each other and form neutral carbon dioxide, water, and a soluble salt

http://ga.water.usgs.gov/edu/images/phdiagram.gif


Demo: Baking Soda v. Powder

• Two beakers (cốc) of water– Add spoonful (thìa, muỗng) of baking SODA

• What happens?

– Add spoonful of baking POWDER• What happens?

• Add a bit of vinegar to the baking soda– What happens?


Chemical leavening

1. Baking soda = Sodium bicarbonate (alkaline)• Add soda to dough containing acid• Get carbon dioxide!

2. Baking powder = Baking soda + acid• Add baking powder to water• Get carbon dioxide!


Leavening: Baking Powder

Baking Powder contains both base and acid– Base: baking soda– Acid: dry crystalline form

• Several different types acid may be present:– Fast acting - during mixing

» Very soluble acid (ex. Cream of tartar-tartaric acid)– Slow release after mixing

» Not very soluble (ex. sodium aluminum pyrophosphate (SAPP))

– Heat activated - during cooking» Soluble only at specific minimum temperatures» Ex. Dimagnesium phosphate (DMP) - 40-44C


DOUGHS AND BATTERS I:


II. Gluten developmentIII. Leavening involves production of CO2 gas

IV. Additional ingredients in doughs

-Shortening: fats and oils that “shorten” gluten-break up gluten masses, weaken structure so final product is more tender

-Sugar: -feeds yeast, binds water to moisten bread, involved in browning reactions

-Salt-inhibits yeast activity, toughens gluten, inhibits gluten proteases

-Milk and eggs-add flavor and texture


Dough components -SUMMARY

• Flour = gluten proteins

• Leavening = CO2 to raise bread

• Shortening = increase volume, tender

• Sugar = tender, brown

• Salt = inhibits gluten proteases inhibits yeast activity toughens up gluten proteins

• Eggs/milk = flavor, structure


Scientific terms/concepts:

• gluten proteins (glutenin and gliaden)– hydrogen, disulfide, hydrophobic bonds– elasticity, plasticity

• wheat enzymes: malt enzymes, proteases

• leavening: biological v. chemical, aerobic v. anaerobic metabolism, acid-base reaction

bio 9b: biology and chemistry of cooking winter 2006 lectures 15: doughs and batters i

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