8/1/2012

More Fun In the Food Science Classroom

Welcome!

• Presenters:– Patti Rambo, Director, The Curriculum Center for Family and Consumer

Sciences, Texas Tech University, Lubbock, TX– Leslie Thompson, Ph.D., Chair and Professor, Department of Animal and

Food Sciences International Center for Food, Texas Tech University, Lubbock, TX

– Sandra Duke, Family and Consumer Sciences Education Graduate Research Assistant, Texas Tech University, Lubbock, TX

Fun In the Food Science Classroom

Molecular Motion

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Fun In the Food Science Classroom

Molecular MotionTEKS (14) The student explains how food

provides energy. The student is expected to:

• (A) discuss molecular motion and temperature

• (D) compare various temperatures on rates of reaction

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Fun In the Food Science Classroom

Molecular Motion• Objective: Student will demonstrate and

explain the effect temperature has on molecular motion.

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Fun In the Food Science Classroom

Molecular Motion• Color Changing Milk Experiment

– One cup of milk on plate – Place food coloring in milk– Place a drop of food coloring

• Variables– Hot milk– Cold Milk

• Hypothesis?

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Fun In the Food Science Classroom

Molecular MotionBrownian Motion • Random movement of atoms and

molecules suspended in a liquid or gas• Motion is caused by collisions with

molecules of the surrounding medium • Heat energy determines how fast

molecules move

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Fun In the Food Science Classroom

Molecular MotionKinetic Theory • Matter is composed of small particles - atoms

and molecules• Particles of matter are in constant vigorous

motion• Helps explain:

– Transfer of heat– Relationship between temperature, pressure and

volume of gases

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Fun In the Food Science Classroom

Molecular MotionDiffusion• Spontaneous spreading out of something• Random in nature • Matter moves constantly!

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Fun In the Food Science Classroom

Foaming and Whipped Cream

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Fun In the Food Science Classroom

Foaming and Whipped Cream TEKS (19) The student understands

coagulation and coalescence process associated with milk protein and cheese. The student is expected to:(F) Identify the factors that affect the ability of cream to form a foam.

8/1/2012

Fun In the Food Science Classroom

Foaming and Whipped Cream Objective: Students will demonstrate and

explain the effects temperature and agitation have on foams formed from cream

8/1/2012

Fun In the Food Science Classroom

Foaming and Whipped CreamWhipped Cream Experiment• Half-cup whipping cream (or other dairy

product of varying fat content)• Place in screw cap plastic container• Shake container vigorously• Check consistency of foam approximately every

2 min• Continue agitation until foam breaks and

butter forms

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Fun In the Food Science Classroom

Foaming and Whipped Cream

Potential variables• Fat content of dairy product (evaporated milk 7.25%

fat, half and half 10 to 18%, light cream 18 to 30%, light whipping cream 30 to 36%, heavy whipping cream >36%)

• Temperature of heavy whipping cream• Time of agitation• Age of whipping cream• Addition of sugar (when added, gradual addition or

dump method)

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Fun In the Food Science Classroom

Foaming and Whipped CreamFoam: Dispersion consisting of a continuous

liquid phase and a discontinuous gas phase

Examples:Ice cream, angel food cake, meringues,

whipped toppings, soufflés

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Fun In the Food Science Classroom

Foaming and Whipped Cream• Foams are formed when whipping or

agitation unfolds (denatures) proteins creating a stable network that traps air

• Agitation unfolds proteins and incorporates air

• Fat in whipping cream helps stabilize the foam

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Fun In the Food Science Classroom

Foaming and Whipped Cream The most stable dairy foams are produced

at lower temperatures.

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Fun In the Food Science Classroom

Egg Foams

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Fun In the Food Science Classroom

Egg Foams TEKS (4) The student analyzes the role of

acids and bases in the food sciences. The student is expected to:

• (E) Discuss ways pH is related to the properties of food, its safety and its freshness

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Fun In the Food Science Classroom

Egg Foams TEKS (18) The student describes the

properties of proteins and amino acids. The student is expected to:

• (F) List factors that affect the stability of egg foam

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Fun In the Food Science Classroom

Egg Foams Objective: The student will assess how pH

affects the physical properties of eggs.

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Fun In the Food Science Classroom

Egg Foams• As shell eggs age they loose water and CO2

• This cause the loss of the carbonate buffer• As the buffer is lost the pH of the egg increases• As pH of albumen increases the thick albumen

becomes thinner• As the albumen thins it foams more easily but

is much less stable

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Fun In the Food Science Classroom

Egg Foams• As eggs are stored the pH increases from

about 7.2 to 9.5 • pH changes affect foamabilty and foam

stability• Ovomucin is the primary protein in eggs

responsible for foaming and foam stability

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Fun In the Food Science Classroom

Egg Foams• Freshly laid eggs are USDA Quality Grade

AA• As eggs are stored the quality grade

decreases from AA A B• Foam stability decreases as quality grade

decreases

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Fun In the Food Science Classroom

Egg Foams• Lipids interfere with egg foaming and

foam volume • Factors such as temperature, age of the

egg, presence of sugars, presence and types of lipids, pH and other ingredients affect foam volume and stability

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Fun In the Food Science Classroom

Curds and Whey

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Fun In the Food Science Classroom

Curds and Whey TEKS (6) The student studies the chemical

properties of food. The student is expected to:

• (H) Analyze the occurrence of specific chemical reactions

• (I) Analyze chemical and physical changes in food

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Fun In the Food Science Classroom

Curds and Whey Objective: The student will generate a

physical change of a substance from a liquid state to a solid state

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Fun In the Food Science Classroom

Curds and WheyThe two major milk proteins are casein and whey.

When milk is acidified to a pH of 4.6 casein becomes insoluble precipitating out of solution

forming curds.

Whey proteins remain soluble (do not denature) at low pH and are found in the liquid that is

separated from the solid curds.

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Fun In the Food Science Classroom

Curds and Whey• Casein exist in milk in the form of soluble

micelles. • Casein consists of three primary forms

– Alpha, beta and kappa• Some portions of the micelle are

hydrophillic others are hydrophobic.• Colloidal CaPO4 is within the micelle.

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Fun In the Food Science Classroom

Curds and Whey• When pH is 4.6 or lower • Colloidal CaPO4 within the micelle is

disrupted and micelle structure changes• The micelle is no longer soluble • The casein proteins then aggregate

forming a gel

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Fun In the Food Science Classroom

Curds and Whey• Cheese making - rennet (chymosin and

pepsin, two enzymes) is used • Kappa casein is cleaved from the casein

molecule• Micelles are destabilized losing solubility • Casein proteins aggregate forming a gel

(curds)

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Fun In the Food Science Classroom

Chemical Leavening

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Fun In the Food Science Classroom

Chemical LeaveningTEKS (6) The student studies the chemical

properties of food. The student is expected to:

• (H) Analyze the occurrence of specific chemical reactions

• (I) Analyze chemical and physical changes in food

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Fun In the Food Science Classroom

(10) The student discusses how leavening agents are used in baking. The student is expected to:

• (A) describe the purpose of leavening agents in baked goods.

• (B) Identify and describe major leavening agents.• (C) explain why baking soda is used with an acid in

baked goods • (F) discuss how air and steam act as leavening agents

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Fun In the Food Science Classroom

Chemical LeaveningObjective: The student will assess the

effectiveness of various types of leavening systems.

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Fun In the Food Science Classroom

Chemical Leavening Chemical leavening systems consist of a leavening agent (produces CO2 gas) and a

leavening acid (provides H+ ions that cause the release of CO2)

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Fun In the Food Science Classroom

Chemical Leavening • Common leavening agent

– Sodium bicarbonate or “baking soda” (NaHCO3)

• Common leavening acids– Acetic acid (vinegar)– Lactic acid– Sodium aluminum sulfate– Monocalcium phosphate

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Fun In the Food Science Classroom

Chemical Leavening • Baking powder contains

– Sodium bicarbonate (leavening agent)– Sodium aluminum sulfate (leavening acid)– Monocalcium phosphate (leavening acid)– “Double acting” baking powder

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Fun In the Food Science Classroom

Chemical Leavening Leavening reaction in an aqueous system:

HCO3- + H+ H2CO3 H2O + CO2

Equilibrium is pH-dependent

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Fun In the Food Science Classroom

Chemical Leavening Carbonic acid-bicarbonate equilibrium

H2CO3 HCO3- + H+ pKa = 6.35

Thus, below pH 6.35 bicarbonate is converted to carbonic acid which in an aqueous system can produce CO2 and water.

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Fun In the Food Science Classroom

Browning Reactions: Maillard Reaction, Caramelization,

and Enzymatic Browning

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Fun In the Food Science Classroom

Browning Reactions - The Maillard Reaction (non-Enzymatic), Caramelization and Enzymatic Browning

TEKS (6) The student studies the chemical property of foods. The student is expected to:

• (H) analyze the specific occurrence of specific chemical reactions.

• (I) analyze chemical and physical changes in foods.

8/1/2012

Fun In the Food Science Classroom

Browning Reactions - The Maillard Reaction (non-Enzymatic), Caramelization and Enzymatic Browning

TEKS (8) Student understands the functions of enzymes. The student is expected to:

• (A) describe how enzymes act as catalysts. • (D) identify factors that affect enzyme activity.• (E) explain how enzyme reactions are involved

in food preparation.

8/1/2012

Fun In the Food Science Classroom

Browning Reactions - The Maillard Reaction (non-Enzymatic), Caramelization and Enzymatic Browning

TEKS (18) The student describes the properties of proteins and amino acids. The student is expected to:

• (C) explain what happens during denaturation of protein and how the process occurs.

8/1/2012

Fun In the Food Science Classroom

Browning Reactions - The Maillard Reaction (Non-Enzymatic), Caramelization and Enzymatic Browning

Objective: The student will summarize the browning reactions.

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Fun In the Food Science Classroom

The Maillard Reaction (Non-Enzymatic)

Substrates: Amino acids + Reducing sugars

Products: Brown pigments + Flavor and odor compounds

Reaction is favored by: • higher pH’s (add baking soda)• intermediate water activity

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Fun In the Food Science Classroom

The Maillard Reaction (Non-Enzymatic)“In other words”

Amino acids + Reducing sugars(Amine groups) (Carbonyl groups) -NH2 H |

- C = O or – C = O | |

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Fun In the Food Science Classroom

N-substituted glycosylamine

ketosamines

aldehydes + ketones (flavor and odor

compounds) + Melanodin

pigments (Brown pigments)

Amadori rearrangement

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Fun In the Food Science Classroom

• Responsible for browning and flavor in:– Roasted coffee– Cooked meat– Sautéed onions

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Fun In the Food Science Classroom

• Sugars vary in their reactivity (most to least reactive):

– Five-carbon sugars – xylose, arabinose– Six-carbon aldoses – glucose, galactose– Six- carbon ketoses – fructose– Reducing disaccharides – lactose, maltose– Non-reducing disaccharide – sucrose (non-reactive)

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Fun In the Food Science Classroom

Caramelization

Heating and dehydration of sugars to produce brown pigments and flavor compounds

• Sucrose melts (160°C) and undergoes pyrolysisSucrose (C12) Glucose (C6) + Fructose (C6)

• Simple sugars condensation and undergo dehydration forming large brown polymers

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Fun In the Food Science Classroom

Caramelization

• Examples of large brown polymers that form as reaction progresses:

– Caramelan (C24)– Caramelen (C36)– Caramelin (C125)

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Fun In the Food Science Classroom

Caramelization

Flavor compounds:• Diacetyl ( 2,3-butanedione) important flavor

compound, produced during the first stages of caramelization. Diacetyl produces a buttery or butterscotch flavor

• Esters and lactones - sweet rum-like flavor• Furans - nutty flavor• Maltol - toasty flavor

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Fun In the Food Science Classroom

Caramelization

• Reaction is responsible for flavor and aroma of:– Caramel candy– Syrups

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Fun In the Food Science Classroom

Enzymatic BrowningReaction catalyzed by the enzyme polyphenol

oxidase

Phenols

+ O2 MelaninPigments

Polyphenol oxidase

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Fun In the Food Science Classroom

Enzymatic Browning

Responsible for browning in:• Sliced bananas, apples, avocados, potatoes• Dried fruit and vegetables• Shrimp, crab, lobster

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Fun In the Food Science Classroom

Enzymatic Browning

Control reaction by: • Denaturing enzyme• Excluding oxygen

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Fun In the Food Science Classroom

Enzymatic Browning

Enzyme denaturation:• Unfolding of protein structure • Enzyme looses activity when denatured

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Fun In the Food Science Classroom

Enzymatic Browning

Enzyme denaturation caused by:• pH extremes (add acids)• Heat (blanching)• Mechanical denaturation (whipping, beating,

kneading)• Many others

8/1/2012

Fun In the Food Science Classroom

Have fun with the science of food!

8/1/2012