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PHY 1600 Exam 2
Terms in this set (95)
Nathan Myhrvold in the 5th chapter of "Modernist Cuisine" describes 4 modes of heat transfer. Match the first three modes listed on the left with the examples he uses for each listed on the right (write the letter of the example in the correct blank on the left.
microwave ovens, broilers and charcoal grills --> Radiation
electric burner through skillet to a piece of bacon --> Conduction
boiling, deep-fat frying oil --> Convection
What is the 4th mode of heat transfer described in this Modernist Cuisine chapter?
In this chapter of Modernist Cuisine, what is the property that describes how bread can go from light brown to flaming in the blink of an eye ... "Changes in _________ are usually to blame when a food at first responds slowly to radiant heat and then suddenly overheats."
The "Heavy Metal" article discusses the care of cast iron skillets. While seasoning the cast iron, he recommends a ______ layer of oil and temperatures ________ 400 F - 500 F to effectively polymerize the oil.
thin, at or above
thin, just below
thick, just below
thick, at or above
thin, at or above
In the article "Heavy Metal - The Science of Cast Iron Cooking" they state that cast iron is a relatively ________ (good or poor) CONDUCTOR as compared to materials like aluminum and copper.
What is the trail of bubbles in bubbly drinks?
What causes nucleation sites?
is super saturated carbon dioxide
What temperature does water need to be at for it to be fizziest
32 degrees, cold water, as the water gets warmer the less fizzy it gets
What is the best type of glass to put champagne in?
_____________ is a critical factor to determine how much CO2 the liquid can absorb
Factors that impact the rate of loss of CO2:
surface area of glass & nucleation sites
Iced tea is great....
example of minimal transport/ minimally packaged beverage as it is typically made it home with tap water, to improve brew energy make iced tea concentrated
Is concentrate or carton juice environmentally better?
Concentrate juices are worse
What kind of carbon footprint does milk have?
high carbon footprint
What kind of beer emits the least/most carbon footprint?
Least: locally brewed cask ale at the pub, Most: bottled beer from this shop extensively transported
For drinks what is the most complicated and energy intensive?
What is the largest greenhouse gas?
1/3 of our food waste comes from packaging
Transparent, completely inert, does not degrade, industrialization of glass making changed our food system, but really heavy
are easier use less energy to intensive to mine, refine, process, transport, and shape into bottles.................. glass has much more material per bottle
Recycling - glass and aluminum
glass how lower recycling rates vs. aluminum
Beer has 3 enemies:
oxidation, light, and heat
- Aluminum reduces oxidation and light better than cans
don't have to refrigerate it until you open it
like milk, OJ
can be recycled after they are shreaded
Why are wine glasses narrow at the top?
its narrow at the top so the things that evaporated get stuck/trapped then when you drink it you get that whif which makes drink better
Factors that determine non-disposable straw experience
durability, appealability, ease of cleaning, flexibility, flow (diameter), thermal conductivity
The recyclability of different straws
hard plastic - not recyclable
stainless steel - recyclable
paper - recyclable
silicone - recyclable but not available in communities
flexible polymer used for straws & bake wear
Thermal Conductivity of straws
stainless steel - 68, sometimes they put a silicone tip so it doesn't get too hot
hard plastic - .25
silicone - .2
paper - 0.05
What is the calorie we read on a nutritional label
it is a kcal
1 cal (food calorie) = 1,000 cal (scientific calories)
- average intake in world is 2,300 kcal per day with 40 grams of protein per day
- U.S. average includes 3,300 kcal per day and about 100 grams of protein, 2/3 of which comes from animal origin
defined as the amount of energy needed to raise 1 gram of water 1 degree celcius
For an isolated...
energy out of one part = energy into another part or heat lost = heat gained
an English unit defined as the energy necessary to raise one pound of water, one degree Fahrenheit
is a device that measures the energy of a sample, this is a type of calorimeter is called a bomb calorimeter it measured the thermal energy released when a substance burns, this is the way the caloric content of foods is measured
The Greenhouse Effect
CO2 concentrations have risen from 280 ppm to around 400 ppm today, 99% of our atmosphere are atmospheric gases Nitrate (N2) and O2, the rest of the gases are greenhouse gases - H2O, CO2, CH4 (methane), the more complex the molecule the molecule the more effective it is at absorbing IR radiation and re-emitting it, sun average surface temperature super hot so really short wavelength/ high energy, carbon dioxide and the temperature of our planet from 800,000 years ago until the present day (super high), temperature of planet is rising but not as high as CO2 because water takes so much thermal energy to heat up change temperature
Tropical deforestation is mostly caused by...
What animal produces most methane?
A greenhouse gas, every thing of methane is equal to 20 molecules of CO2, 10% or 12% of U.S. total emissions is due to beef
What is the majority if corn and soy grown in the world....
feeds cattle, pigs, and chickens
Huge inefficiencies in grain b/c
2-5 times more grain is required to produce the same amount of calories through livestock as through grain consumption, it's as much as 10 times more in the case of grain-fed beef in the U.S.
Limits of Food Chains
energy captured by producers usually passes through no more than 4 of 5 trophic levels, the length of food chains is restricted by the inefficiency of energy transfers, !!!!!!!!!!! only 10% of energy in an organism at one trophic level ends up in tissues of an organism at the next trophic level, we are always losing energy when we move up the food chain
Consumption of meat and beans, legumes, nuts
we're overconsuming our meat % and undereating % of beans, nuts, legumes, most methane comes from our livestock
Feed Conversion Ratio
a measure of how efficiently a kilogram of animal feed is converted into animal weight or biomass, Chicken and salmon are efficient in energy retention !!!!!!!!!!!!
eggs can serve multiple purposes like be used to thicken, emulsify, clarify, bind, coat, leaven, and even color food products, can serve as interfering agent or as main ingredient
branch of physics that deals with deformation and flow of matter especially the non-newtonian flow of liquids and the plastic flow of solids
fish provide 17% of animal protein consumed globally, rich in micronutrients, contains some of the nutrient that few things do, the one things that's wild picked, with going up the food chain you have biomagnification
light is an electromagnetic wave,
peak to peak
how disturbed we make it
process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water. in plants it generally involves the green pigment chlorophyll and generates as oxygen as a byproduct, earths plants capture 3 trillion kwh solar energy each day, about 20 times more than we need
Plants are green...
because chlorophyll reflects , rather than absorbs middle of the light spectrum
Nick Lane says that b/c
chlorophyll powers the photosynthetic reaction by absorbing and transferring energy from light but according to Nick Lane it only absorbs blue & red light only actually uses red stuff which is the lower energy of the two, it wastes a lot of sunlight, maximum efficiency would require black leaves
Prevailing theory for photosynthesis and why chlorophyll uses red light not blue
higher energy wavelengths of light are just too hot to handle, damaging a plants photosynthetic machinery, most energy lost due to photons outside 400-700 mm active range, only 5.4% net leaf efficiency thats what they use to make it
Photosynthetic recovery time
20% of energy is lost in the recovery time, got a 15% increase in size when speeding this up
Beef and greenhouse gases
raising livestock accounts for nearly 15% to 50% of global greenhouse gases emitted each year, on average 50 grams of protein each day needed for adult but capita consume 68 grams per day by we eat 90 grams, lentils higher than 1/4 cup of beef in protein
are the largest consumed food, great source of fiber, carbohydrate folate, minerals, same area of farmland you get 2-4 times more than food than other cereal grains, they're more efficient, very hearty, grows in lots of elevations and land needs water to grow, not a massive global trade in transportation typically produced and consumed locally, good storage keep for long time with no processing
myoglobin gives the beef flavor and smell of it, proteins are driving the texture of the meat, coconut stand in for fat
endosperm - most of it, the part that flour is only made of, quick energy all the time, basically all carbs
Germ - smallest part of kernal, will became the new plant, most nutritious part, protein powerhouse, most limitation for shelf life of flour
outside of kernal, has good nutrition, rich in fiber, can be crushed up in whole wheat flour and can rupture air gaps so it doesn't rise as much
using whole wheat flour helps reduce food waste
in order for the bread to rise there needs to be good gluten structures, so that the bubbles are resilient to hold up and allow the bread to rise, the fiber of whole wheat can puncture these bubbles which is why white bread rises more, kneading dough increase the interactions and bonds formed between chains of gluten improving the elasticity of the lattice
when it rises, the release of CO2 as the yeast feasts on sugar this happens before you put in the oven and when it's in the oven, before bread reaches 120 f when yeast dies
once in oven, gas trapped increases in temperature and that results increased volume, the phase change of the liquid water in dough into water vapor also allows these bubbles to expand
cutting top of bread right before it goes in the oven allows for the steam to escape in prescribed locations rather than rupturing the crust in random location
Bread as pressure cooker
crust of bread acts as tiny pressure cooker, air pockets provide a place for steam to form and since steam gets considerably hotter than water, never exceeds the boiling point, helps to move completely cook the starches higher temps cook these
Why is steam oven helpful for bread baking?
allows for more oven spring because it allows bread to expand further before the rust is set, carmelization of sugards in crust in steamy environment the moisture dissolves the sugars on the crust and then as crust dries, these sugars carmelize, giving that brown crispy crust allowing bread to stay crunchy after it cools
Dough & Batter
Dough - is malleable, yeast leavened
Batter - is typically pourable, baking powder leavened
controlling the nucleation sites for the liquid to solid phase change, incorrectly- white film, chalky texture correctly- smooth, not chalky, dark brown
we want them to be very small, higher melting point, get them by tempering, melted then cooled quickly
we want to delay the making of crystals, have a mate finish, as soon as the shininess goes away you know the crystallization is happening/ crystals are forming, ensuring crystals don't form until you want them to
Genetically Modified Organisms (GMOs)
an organism produced through a genetic modification, most of our food are GMOs, have potential to benefit crops, to withstand many types of weather, scientists don't think GMOs are a big health problem
when DNA snips come from the same species
when DNA comes from completely different plant or animal
Caterpillars have a lot of...
Bugs are high in...
protein and some calcium
Lab grown meat lacks one central element
Fat - these bring the flavors and textures, are hard to achieve
to prepare food by the use of heat as by boiling, baking, or roasting
Michael Pollan said cooking always affecting a transformation (psychological & chemical) that helps us enjoy something we might otherwise not be able to stomach
Bee Wilson said food is the great human universal nothing is sure in the world but death and taxes should really be death and food
What makes human species special?
have memory, judgement, and passions, we can cook
The cooking hypothesis
an attempt to account for the dramatic change in primate physiology - larger brains, smaller digestive system, that occurred in Africa approximately 1.8 million years ago with the emergence of homo-erectus , our evolutionary predecessor, cooked food can harness more of its energy, chewing raw meat causes to lose calories that you gain, life is about energy we rely on external energy
Michael Pollan said 3 Gastronomical Revolutions in human history
1. humans began cooking over fire... a community experience
2. Next, with discovery of cooking vessels boiling allowed cooking to more into the house... a family experience
3. Most recently the microwave oven allows us for the first time to cook with a new form of heat transfer (radiation)... an individual experience you don't cook for a family
What is considered a "second stomach"
a cooking vessel, digests so we can eat
- cookbooks are a great witness to history, asia made many cooking pots
Microwaves got popular...
why your pan handle gets hot, the transfer of energy through a material without any motion of the material as a whole, cooking on electric resistance burner or induction cooktop or oven all cooking with conduction, thermal conductivity through lattice vibration, highly conductive surfaces can reduce thawing time (aluminum is high!!! Polyethylene is low!), heat by conduction = K area X difference in temperature / thickness
flat lines, sometimes called a mode of thermal energy
(K) a physical property that describes how fast a given material can move heat around, materials with good thermal conductivity are able to transfer heat from one part of the pan to another very quickly and efficiently, which provides even heat, metals and gases are good conductors, is in units of Watt/ (mK), kelvin is a measure of temp. we can see thermal conductivity is a measure of how much thermal power moves through a distance due to a temperature difference
natural currents for current for boiling water, the transfer of energy through a material by this movement of the material itself, cooking in convection oven, halogen convection oven and solar dehydrates are example of cooking with convection, 2 types of convection
- Forced convection : use fan or blower to force convection, convection oven
- Natural convection : natural currents induced by density difference create convection, water at bottom gets hotter faster bottom layer less dense than colder upper level so that sinks down, warm low density fluid rises
example is the candle ash tea bags
Different metals and their thermal conductivity
- steel more conductive than steel
Most --> least
- copper - aluminum - iron - stainless steel - glass
Forced & natural Convection
stirring, natural convection-can lead to "boundary layers" around food which creates a type of insulating layer, this forms when friction btwn food and the cooking medium slows the movement of this cooking medium, if you disturb this boundary layer-sitr the medium- you can greatly speed up the cooking process
Heat Transfer Coefficient
similar to diffusivity for conduction, term that combines convection, density, viscosity and flow velocity of the fluids involved, in general forced convection increases the heat transfer coefficient by tenfold or more
why you can feel the fire through gap between you and fire, the transfer of energy by the emission of electromagnetic waves, which carry energy away from the emitter, cooking in microwave, boiling, grilling, and solarcooking, all matter emits thermal radiation all the time, it's emitted by atoms and molecules which having absorbed energy release it again not in the form of faster movement (kinetic energy) but as pure (radiant energy)
- radiation is created by the movement of electrically charged particules often electrons within atoms.
- this movement creates electrical and magnetic fields that radiate or spread out as waves
- conversely when such energetic waves his other atoms they cause increased movement in those atoms
The Electromagnetic spectrum
most cooking goes on in the infrared region, emissivity - close to o =low close to 1= high, why things overcook - changes in reflectivity are usually to blame when food at first responds slowly to radiant heat and then suddenly overlooks
they tend to react chemically with foods and produce undesireable results, highly reactive cookware materials include iron copper aluminum and carbon steel, noreactive cookware materials include stainless steel and enamal, materials that are highly reactive also tend to have highly desireble thermal properties
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