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8/1/2012. Welcome! Presenters: – Patti Rambo, Director, The Curriculum Center for Family and Consumer Sciences, Texas Tech University, Lubbock, TX – Leslie.

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Presentation on theme: "8/1/2012. Welcome! Presenters: – Patti Rambo, Director, The Curriculum Center for Family and Consumer Sciences, Texas Tech University, Lubbock, TX – Leslie."— Presentation transcript:

1 8/1/2012

2 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

3 Molecular Motion 8/1/2012

4 Molecular Motion TEKS (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

5 Molecular Motion Objective: Student will demonstrate and explain the effect temperature has on molecular motion. 8/1/2012

6 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

7 Molecular Motion Brownian 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

8 Molecular Motion Kinetic 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

9 Molecular Motion Diffusion Spontaneous spreading out of something Random in nature Matter moves constantly! 8/1/2012

10 Foaming and Whipped Cream 8/1/2012

11 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

12 Foaming and Whipped Cream Objective: Students will demonstrate and explain the effects temperature and agitation have on foams formed from cream 8/1/2012

13 Foaming and Whipped Cream Whipped 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

14 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

15 Foaming and Whipped Cream Foam: 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

16 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

17 Foaming and Whipped Cream The most stable dairy foams are produced at lower temperatures. 8/1/2012

18 Egg Foams 8/1/2012

19 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

20 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

21 Egg Foams Objective: The student will assess how pH affects the physical properties of eggs. 8/1/2012

22 Egg Foams As shell eggs age they loose water and CO 2 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

23 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

24 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

25 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

26 Curds and Whey 8/1/2012

27 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

28 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

29 Curds and Whey The 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

30 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 CaPO 4 is within the micelle. 8/1/2012

31 Curds and Whey When pH is 4.6 or lower Colloidal CaPO 4 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

32 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

33 Chemical Leavening 8/1/2012

34 Chemical Leavening 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

35 (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

36 Chemical Leavening Objective: The student will assess the effectiveness of various types of leavening systems. 8/1/2012

37 Chemical Leavening Chemical leavening systems consist of a leavening agent (produces CO 2 gas) and a leavening acid (provides H + ions that cause the release of CO 2 ) 8/1/2012

38 Chemical Leavening Common leavening agent – Sodium bicarbonate or “baking soda” (NaHCO 3 ) Common leavening acids – Acetic acid (vinegar) – Lactic acid – Sodium aluminum sulfate – Monocalcium phosphate 8/1/2012

39 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

40 Chemical Leavening Leavening reaction in an aqueous system: HCO H + H 2 CO 3 H 2 O + CO 2 Equilibrium is pH-dependent 8/1/2012

41 Chemical Leavening Carbonic acid-bicarbonate equilibrium H 2 CO 3 HCO H + pKa = 6.35 Thus, below pH 6.35 bicarbonate is converted to carbonic acid which in an aqueous system can produce CO 2 and water. 8/1/2012

42 Browning Reactions: Maillard Reaction, Caramelization, and Enzymatic Browning 8/1/2012

43 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

44 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

45 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

46 Browning Reactions - The Maillard Reaction (Non-Enzymatic), Caramelization and Enzymatic Browning Objective: The student will summarize the browning reactions. 8/1/2012

47 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

48 The Maillard Reaction (Non-Enzymatic) “In other words” Amino acids+ Reducing sugars (Amine groups) (Carbonyl groups) -NH 2 H | - C = O or – C = O | | 8/1/2012

49 N-substituted glycosylamine ketosamines aldehydes + ketones (flavor and odor compounds) + Melanodin pigments (Brown pigments) Amadori rearrangement 8/1/2012

50 Responsible for browning and flavor in: – Roasted coffee – Cooked meat – Sautéed onions 8/1/2012

51 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

52 Caramelization Heating and dehydration of sugars to produce brown pigments and flavor compounds Sucrose melts (160°C) and undergoes pyrolysis Sucrose (C12) Glucose (C6) + Fructose (C6) Simple sugars condensation and undergo dehydration forming large brown polymers 8/1/2012

53 Caramelization Examples of large brown polymers that form as reaction progresses: – Caramelan (C24) – Caramelen (C36) – Caramelin (C125) 8/1/2012

54 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

55 Caramelization Reaction is responsible for flavor and aroma of: – Caramel candy – Syrups 8/1/2012

56 Enzymatic Browning Reaction catalyzed by the enzyme polyphenol oxidase Phenols + O2O2 Melanin Pigments Polyphenol oxidase 8/1/2012

57 Enzymatic Browning Responsible for browning in: Sliced bananas, apples, avocados, potatoes Dried fruit and vegetables Shrimp, crab, lobster 8/1/2012

58 Enzymatic Browning Control reaction by: Denaturing enzyme Excluding oxygen 8/1/2012

59 Enzymatic Browning Enzyme denaturation: Unfolding of protein structure Enzyme looses activity when denatured 8/1/2012

60 Enzymatic Browning Enzyme denaturation caused by: pH extremes (add acids) Heat (blanching) Mechanical denaturation (whipping, beating, kneading) Many others 8/1/2012

61 Have fun with the science of food! 8/1/2012


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