 Again, how does heat move into food?  What are critical temperatures?  How can you use sous vide to manipulate cooking temperatures?

 Say you want a hard-boiled egg with a solid yolk; the transition temperature for the yolk to be well-coagulated is about 70  C. How long does it take for the heat to reach the center of an egg with a radius of 2cm after the egg is immersed in boiling water? Use the equation of the week.

 Why are these reactions important?  What food components are involved in each?  What temperature do they happen at?  How could you increase the rate of these reactions?

 Even in a hot oven, most foods do not go over 100  C. Why not? What would you expect the temperature curve to look like once the equation of the week says the temperature should be above 100  C?

 Force of fluids that resists flow  What determines this?  The time it takes for molecules to move around their neighbors. ▪ What does a longer time mean? Shorter?  Equation of the week   Elasticity x relation time  Units?

 Think milkshake lab  What things did we need to measure and why? d

 Distance ball dropped & time it took ball to drop can be used to calculate terminal velocity  What is terminal velocity?  Drag = Gravitational  In other words, ▪ Drag – gravitational = 0 ▪ No net force!! V T = d/t Drag force Gravitational force

 Gravitational force:  How buoyant the object is  In other words   Drag force  Depends on viscous flow

 Again think of what it means to be at terminal velocity… no net force!  So you can set drag and gravitational forces equal to each other F Drag F Gravity

 What happens to a feather and bowling ball falling in a vacuum?

 Pay attention to units! FluidViscosity [mPa s] (at 20°C) liquid nitrogen0.2 water1 milk2 blood10 cream20-40 olive oil honey2,000-3,000 yogurt25,000 dough100, ,000

 Starch example: Higher temperature

 Protein example: ThickeningCurdling

 Polymers = long chains of monomers  Examples?  Proteins (monomers = amino acids)  Complex carbs (monomers = simple sugars such as glucose)

 How do you calculate the effective size of a polymer?  Size = sqrt (# monomers*size monomer) ▪ Size monomer can be estimated by its area  What does calculating the size of a polymer take into account that just calculating its length does not?

 Mixture of droplets of one liquid dispersed within another liquid Oil-in-water Direct emulsion Water-in-oil Indirect emulsion

 What are some problems with making emulsions such as mayonnaise or aioli?  How can emulsions “fail”?  How do chefs use other ingredients to manipulate the chance of failure?

hydrophilic likes water hydrophobic likes oil Stabilize by lowering surface energy

 Surfactants = Ampiphilic molecules

What does it mean conceptually to have a higher volume fraction? What is the critical volume fraction?

Emulsions are elastic above the critical volume fraction

What’s the critical volume fraction? How would you increase the elasticity? How would you decrease it?

How do foams fail? How do you stabilize them?

 Include instructions and ingredients  Ingredients come in different ratios What constrains sets of recipes?

 What reactions have we seen already?  Digestion  Phase transition (more a physical reaction) ▪ On that note, what’s the difference between physical * chemical reactions?  Spherification  Etc.

 Air, steam, yeast and chemical  Chemical  Baking soda and baking powder  What’s the difference?

 Basic reaction  Base + acid  gas  Baking soda + vinegar  gas  Sodium bicarbonate + acetic acid  sodium acetate + water + carbon dioxide Equation must be balanced! What does this mean?

 How much gas (volume) will 1 tsp of baking soda produce?  Assume for simplicity, 1 tsp ~ 5g  Molecular weight of baking soda = 84g/mol

 First calculate # moles of baking soda  [0.06 moles]  Since 1: 1 ratio  0.06 moles of CO2 produced  Calculate corresponding volume  1 mole of any gas at STP = 22.4L  So 0.06 * 22.4 = 1.3 L  Will a loaf of bread with this amount of baking soda actually rise this much?

 Baking powder is baking soda + cream of tartar

 Carmelization  Maillard  Fruit  What’s interacting in each of these?  What are some ways to increase browning reactions?

 Carmelization  Happens at 150C between sugars  Maillard  Happens at 120C between amino acids and carbs  Can increase this & carmelization by adding baking soda  Fruit  Enzymes cause the oxidation of phenolic compounds  Can increase by reaching the optimal temperature or adding salt and decrease by lowering temperature, lowering pH or raising it until the enzymes denature

 Happens exponentially

 Let’s say there is one E. coli bacteria in your spinach salad. It has a generation time of 0.35 hours. How long would it take to be unsafe to eat according to the USDA (100,000)?

 If your eggs started out with 1 million Salmonella microbes, how long would you need to pasteurize them to reduce them to a USDA safe amount (reduction to 10^-6.5)? .5 hours = division time

 Environment  pH  Temperature  Food

 Yeast  Digestive microbes  Uses  Preservation  Flavor intensification  Intoxication

 Can preserve vegetables  Olives, kimchi, sauerkraut  Brewer’s yeast  Converts sugar to alcohol (form of self defense actually) Glucose  carbon dioxide + ethanol C 6 H 12 O 6  2CO 2 + 2CH 3 CH 2 OH

 Pay attention to how the molar coefficients on this example are different (1  2) than in a baking soda reaction where it’s a 1:1 ratio Glucose  carbon dioxide + ethanol C 6 H 12 O 6  2CO 2 + 2CH 3 CH 2 OH The molar coefficients are there to balance the number of C’s, H’s and O’s (as well as any other atoms) in the reactants and the products.

 How much alcohol would a starting grape juice with 500g of sugar produce?  MW sugar = 180g  MW alcohol = 46g  If you had 1000g of wine as a final product, what would the alcohol content be?  Is this realistic?

 Also seen in milk  Yogurt, sour cream, buttermilk