8/1/2012
Feb 25, 2016
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Molecular Motion• Objective: Student will demonstrate and
explain the effect temperature has on molecular motion.
8/1/2012
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?
8/1/2012
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Molecular MotionDiffusion• Spontaneous spreading out of something• Random in nature • Matter moves constantly!
8/1/2012
Fun In the Food Science Classroom
Foaming and Whipped Cream
8/1/2012
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
8/1/2012
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)
8/1/2012
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Foaming and Whipped Cream The most stable dairy foams are produced
at lower temperatures.
8/1/2012
Fun In the Food Science Classroom
Egg Foams
8/1/2012
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Egg Foams Objective: The student will assess how pH
affects the physical properties of eggs.
8/1/2012
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
8/1/2012
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
8/1/2012
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Curds and Whey
8/1/2012
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
8/1/2012
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
8/1/2012
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.
8/1/2012
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.
8/1/2012
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
8/1/2012
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)
8/1/2012
Fun In the Food Science Classroom
Chemical Leavening
8/1/2012
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Chemical LeaveningObjective: The student will assess the
effectiveness of various types of leavening systems.
8/1/2012
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)
8/1/2012
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Chemical Leavening Leavening reaction in an aqueous system:
HCO3- + H+ H2CO3 H2O + CO2
Equilibrium is pH-dependent
8/1/2012
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.
8/1/2012
Fun In the Food Science Classroom
Browning Reactions: Maillard Reaction, Caramelization,
and Enzymatic Browning
8/1/2012
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.
8/1/2012
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
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
• Responsible for browning and flavor in:– Roasted coffee– Cooked meat– Sautéed onions
8/1/2012
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)
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Caramelization
• Examples of large brown polymers that form as reaction progresses:
– Caramelan (C24)– Caramelen (C36)– Caramelin (C125)
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Caramelization
• Reaction is responsible for flavor and aroma of:– Caramel candy– Syrups
8/1/2012
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
8/1/2012
Fun In the Food Science Classroom
Enzymatic Browning
Enzyme denaturation:• Unfolding of protein structure • Enzyme looses activity when denatured
8/1/2012
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