PHY123 final exam
what is the name of the bond that forms between water molecules and is constantly being broken when water is in its liquid state? a. hydrogen bond b. van der Waals bond c. covalent bond d. ionic bond
hydrogen bond
If you hike up a high mountain and cook a box of spaghetti at that higher elevation, you will find ... a. ... it takes more time to cook. b. ... it takes less time to cook. c. ... it never cooks. d. ... it tastes like chicken.
a. ... it takes more time to cook.
How many teaspoons of water contain 1.65x1023 water molecules? Note the molar mass of water is 18 g/mol. The mass of a cup of water is 237 grams. See Equation Sheet for other conversions. a. 1 teaspoon b. 5 teaspoons c. 10 teaspoons d. 50 teaspoons
a. 1 teaspoon
A gel forms when the gelatin concentration is sufficiently high. With enough gelatin molecules in the liquid, their long chains can overlap with each other to form a continuous network. At what concentration is the number of gelatin molecules sufficiently high such that a gel forms? a. 1% b. 50% c. 64% d. 80%
a. 1%
Which of the following statements is true? a. A difference in temperatures of 10°C is equivalent to a difference in temperature of 10 K. b. A difference in temperatures of 10°F is equivalent to a difference in temperature of 10 K. c. A difference in temperatures of 10°C is equivalent to a difference in temperature of 10°F. d. None of the above.
a. A difference in temperatures of 10°C is equivalent to a difference
Which weighs more (has more mass) one mole of sugar molecules or one mole of water molecules? a. A mole of sugar molecules b. A mole of water molecules c. A mole of sugar molecules weighs the same as a mole of water molecules
a. A mole of sugar molecules
Brining is the process of submerging a cut of meat in a brine solution, which is simply salt dissolved in water. The meat absorbs extra liquid and salt, resulting in a juicier and more flavorful final dish. This technique is particularly great for lean cuts of meat that tend to dry out during cooking. Which of the following words best describes the motion of the salt in the meat? a. Diffusion b. Viscosity c. Gelation d. Dispersion
a. Diffusion
Some common thickening agents used in cooking are xanthan gum, gelatin, pectin, alginate, egg, starch, and flour. What do these molecules have in common? a. Each of these ingredients contains long polymers. b. Each of these ingredients has primarily globular molecules. c. Each of these ingredients is also a gelling agent. d. Each of these ingredients is composed primarily of polysaccharides.
a. Each of these ingredients contains long polymers.
How is fish collagen different from mammal or bird collagen? a. Fish collagen is less cross-linked, and so melts and dissolves at much lower temperatures. b. Fish collagen is more cross-linked, and so melts and dissolves at much higher temperatures. c. Fish collagen has a volume fraction more than the critical volume fraction, unlike mammal or bird collagen. d. Fish collagen has a volume fraction less than the critical volume fraction, unlike mammal or bird collagen.
a. Fish collagen is less cross-linked, and so melts and dissolves at much lower temperatures.
Jell-O is a type of gel. What is in the continuous phase? a. Gelatin b. Water c. Sugar d. Salt
a. Gelatin
What is the relationship between gelatin and collagen? a. Gelatin comes from collagen. b. Collagen comes from gelatin. c. Collagen and gelatin are the same thing. d. Gelatin is a fat whereas collagen is a protein.
a. Gelatin comes from collagen.
What role does the enzyme chymosin, found in rennet, play in cheese production? a. It allows the micelles of casein proteins to become uncharged and form a continuous meshwork. b. It produces lactic acid that curdles the milk. c. It attacks the DNA of viruses making cheeses safe to eat. d. It stabilizes the fat globules so the milk does not separate.
a. It allows the micelles of casein proteins to become uncharged
A droplet of oil with a diameter of 5 cm is in water. It is whisked and broken into many smaller droplets with a diameter of 1 mm. Why is so much energy required in the whisking process to breakup the drops? a. It takes energy to increase the surface area between the oil drops and the water. b. It takes energy to heat up the oil so that it will breakup into smaller drops. c. It takes energy to bring the oil, which is at a lower density, down into the water, which is at a higher density.
a. It takes energy to increase the surface area between the oil drops and the water.
Unlike fats, starches can dissolve in water. What can you infer about starches from this property? a. Starches are polar. b. Starches are nonpolar. c. Starches have a large molar mass. d. Starches have a small molar mass.
a. Starches are polar.
How does a pressure cooker change the boiling point of water? a. Steam builds up inside, increasing the pressure and thus raising the boiling point. b. Steam builds up inside, increasing the pressure and thus lowering the boiling point. c. A vacuum is applied, lowering the pressure and thus raising the boiling point. d. A vacuum is applied, lowering the pressure and thus lowering the boiling point
a. Steam builds up inside, increasing the pressure and thus raising the boiling point.
If a steak is overcooked, it becomes tough and rigid. What is happening to the elastic modulus? a. The elastic modulus of the steak is increasing. b. The elastic modulus of the steak is decreasing. c. The elastic modulus of the steak is remaining constant.
a. The elastic modulus of the steak is increasing.
What is kinetic energy? a. The energy of motion. b. The chemical energy that holds molecules together. c. The stored energy in carbohydrates that provides potential energy to do work. d. The stored energy in fats that provides potential energy to do work.
a. The energy of motion.
Free fat or oil (i.e. not emulsified) can make foams unstable. Why? a. The free fat or oil will go to the interface between the water and air and prevent emulsifiers from settling there and stabilizing it. b. The free fat or oil will lead to a density mismatch with the water in the foam. The water will drain down but the oil will rise to the top of the foam. As the oil accumulates at the top of the foam, its weight will crush the foam. c. The free fat or oil will form bonds with the air bubbles in the foam which will increase the weight of the bubbles causing them to sink and burst. d. The free fat or oil will begin to heat up when exposed the air. The added heat in the foam will lead to pressure fluctuations inside the air bubbles, causing them to burst.
a. The free fat or oil will go to the interface between the water and air and prevent emulsifiers from settling there and stabilizing it.
If the elastic modulus of a food is increasing, but the interaction energy is remaining constant, how must the bond density (i.e. the number of bonds in the food) be changing? a. The number of bonds is increasing. b. The number of bonds is decreasing. c. The number of bonds is remaining constant.
a. The number of bonds is increasing.
Sometimes a recipe calls for cream of tartar or lemon juice to be added to egg whites at the beginning of the beating process. Why? a. The acid boosts the flavor profile of the egg-white foam given it a 'brightness.' b. The acid increases the viscosity of the egg whites leading to the foam being more stable since it takes longer to drain. c. The acid boosts the number of free-floating hydrogen ions in the egg white, which makes it harder for bonds to form between proteins that lead to the clustering of proteins and foam failure. d. The acid brakes down the water molecules into hydrogen and oxygen gas which then inflates the foam.
a. The sugar forms crystals that can penetrate living cells membranes making it inhospitable to microbes.
True/False: Liquid foams would last longer in outer space. a. True, because the loss of the gravitational force would reduce the thinning of the bubbles walls over time. b. False, because the process of coalescence would be unchanged in space.
a. True, because the loss of the gravitational force would reduce the thinning of the bubbles walls over time.
Amylose and amylopectin are starch molecules. The shapes of amylose and amylopectin molecules have a direct effect on their ability to thicken a sauce. Which is a better thickener: the compact bushy amylopectin molecule or the long straight amylose molecule? a. amylose b. amylopectin c. the shape doesn't matter, just the mass of the molecule
a. amylose
A cup of water can be cooled by adding ice cubes. As the water becomes colder, the average kinetic energy of the water molecules is____. a. decreasing b. increasing c. remaining constant d. cannot be determined
a. decreasing
A calorie is a unit of____ . a. energy b. fat content c. mass d. temperature
a. energy
Which of the following is not a microorganism? a. enzyme b. yeast c. mold d. bacteria
a. enzyme
The only carbohydrate found in any quantity of milk is____. a. lactose b. casein c. whey d. micelle
a. lactose
The Maillard reaction requires which two macromolecules? a. proteins and carbohydrates b. lipids and water c. proteins and water d. water and carbohydrates
a. proteins and carbohydrates
Which of the following foods has the largest elastic modulus? a.Rock candy. b.String cheese. c.Pancakes. d.White bread.
a.Rock candy.
Temperature is a measure of what molecular property of a food? a.The molecules moving and colliding with each other. b. The molecules sticking to each other. c. The molecules creating a vacuum around each other. d. The molecules undergoing chemical reactions with each other.
a.The molecules moving and colliding with each other.
In a liquid foam, the dispersed phase is____ and the continuous phase is____ . a. .... liquid droplets ... a liquid. b. .... air bubbles ... a liquid. c. ... solid particle ... a liquid. d. ... liquid droplets ... air.
b. .... air bubbles ... a liquid.
Students attempt to make homemade mayonnaise. They estimate the droplets in the mayonnaise to have a radius of 1 mm. In addition, using a reference, they estimate the surface tension to be 0.24 N/m. Finally, based on the ingredients used, they estimate the volume fraction of vegetable oil in the mayonnaise to be about 80%. What is the approximate elasticity of the mayonnaise? Assume the critical volume fraction to be 0.64 or 64% and be careful with units! a. 1 to 10 Pa b. 10 to 100 Pa c. 100 to 1000 Pa d. 1,000 Pa to10,000 Pa e. 0 Pa
b. 10 to 100 Pa
What is the difference between an atom and a molecule? a. An atom is made up of molecules. b. A molecule is made up of atoms. c. They are the same thing. d. Nobody knows.
b. A molecule is made up of atoms.
Which of the following statements is true about gelatin? a. Gelatin cannot be denatured but remains in a globular form. b. After being denatured, gelatin molecules forms weak bonds with each other. c. Upon heating gelatin breaks down into smaller molecules called collagen.
b. After being denatured, gelatin molecules forms weak bonds with each other.
What changes occur in droplets due to coalescence? a. Small droplets get smaller and large droplets get larger. b. Droplets combine to form even larger droplets. c. Droplets float to the top of the liquid.
b. Droplets combine to form even larger droplets.
When you marinate food such as meat or tofu, how does the marinade move through the food? a. Instantly, all at once b. From the outside toward the center c. Slowly, but evenly throughout all parts of the food at the same time d. From the inside out
b. From the outside toward the center
A fillet of tuna is cooked in a pan. How does heat move through the tuna? a. Heat moves at a constant speed through the tuna. b. Heat undergoes a random walk through the tuna. c. Heat starts moving through the tuna slowly, but speeds up the farther it gets in the tuna. d. Heat first propagates around the surface of the tuna and then starts moving towards the center of the tuna.
b. Heat undergoes a random walk through the tuna.
A suspension is composed of monodispersed spheres in water. If each sphere were to shrink and reduce its radius in by a factor of 2, how would the volume fraction change? The volume and surface area of a sphere is provided on the equation sheet. a. It would remain unchanged. b. It would decrease. c. It would increase.
b. It would decrease.
Orange juice has a pH of around 3, whereas black coffee has a pH of around 5. How does the number of hydrogen ions in orange juice compare with black coffee? a. Orange juice has 2x more hydrogen ions than black coffee. b. Orange juice has 100x more hydrogen ions than black coffee. c. Black coffee has 2x more hydrogen ions than orange juice. d. Black coffee has 100x more hydrogen ions than orange juice.
b. Orange juice has 100x more hydrogen ions than black coffee.
An identical amount of peanut oil and water are heated. If the same amount of thermal energy goes into each fluid, which one is hotter? a. They should have the same temperature. b. Peanut oil is hotter. c. Water is hotter.
b. Peanut oil is hotter.
Why does stretched dough creep back to its original shape? a. The electric attraction between the individual gluten molecules. b. The coiled spring like structure of individual gluten molecules. c. The hydrophobic ends of the gluten molecule. d. The hydrophilic ends of the gluten molecule.
b. The coiled spring like structure of individual gluten molecules.
Why does slow-cooked meat, long braises, stews, and barbecues taste tender even though the muscle fibers, which have been cooked for a long time, are very dry and stiff? a. Dry and stiff meat taste tender. b. The collagen in the connective tissue dissolves into gelatin. c. The carbohydrates in the meat breakdown into simple sugar molecules. d. The water is squeezed out of the muscle fibers and tenderize the meat.
b. The collagen in the connective tissue dissolves into gelatin.
Overcooked eggs become both rubbery and watery. Why? a. The high temperature leads to water evaporating inside the egg. b. The protein network becomes overdeveloped and squeezes out the water. c. The high temperature converts the starch in the egg into water.
b. The protein network becomes overdeveloped and squeezes out the water.
Flour or cornstarch is sometimes used as a thickening agent. Which descriptions accurately depicts how flour thickens a sauce. a. The gelatin in the flour forms crosslinks as the sauce cools and a mesh network develops. b. The starch granules absorb a great deal of water and becomes amorphous networks of starch and water intermingled. c. The flour emulsifies the oil in the sauce thus forming oil droplets and thickening it. d. The flour releases carbon dioxide that form bubbles in the sauce and thickens it.
b. The starch granules absorb a great deal of water and becomes amorphous networks of starch and water intermingled.
Why does sugar preserve fruits? a. The sugar forms crystals that can penetrate living cells membranes making it inhospitable to microbes. b. The sugar binds up water and draws moisture out of living cells making it inhospitable to microbes. c. The sugar makes the fruit sweet to eat making it inhospitable to microbes. d. The sugar increases the acidity of the fruit preserve making it inhospitable to microbes.
b. The sugar binds up water and draws moisture out of living cells making it inhospitable to microbes.
Heat flux is the rate of thermal energy loss or gain. As a cup of coffee cools, it loses thermal energy. What are the key factors to consider when determining the heat flux? a. The grinding process for the beans prior to brewing. b. The temperature difference between the coffee and the surroundings. c. The type of coffee beans used to make the coffee. d. The Maillard reaction when the beans are roasted.
b. The temperature difference between the coffee and the surroundings.
On a candy thermometer, different temperature ranges are labeled with different types of syrups. For example, hard ball occurs at about 240°F to 265°F and is used to make marshmallows. Hard crack occurs between 300°F to 310°F and is used to make butterscotch. Why does the type of syrup depend on upon temperature? a. As the syrup is heated, the proteins are denatured and coagulate. The higher temperature results in more denatured proteins and a stiffer syrup when cooled. b. The temperatures refer to the boiling temperature of the syrup, which depends upon the sugar concentration. As the sugar concentration increases, so does the boiling point. Thus each label represents a different sugar concentration. c. The fat globules in the liquid breakdown and thicken the syrup. The higher the temperature, the more fat globules that are broken down. d. The strength of the hydrogen bonding in the water depends on temperature. As the higher increases, the hydrogen grow stronger and the liquid thickens.
b. The temperatures refer to the boiling temperature of the syrup, which depends upon the sugar concentration. As the sugar concentration increases, so does the boiling point. Thus each label represents a different sugar concentration.
Starch is often used to thicken a sauce. When starch is added to a sauce, the starch granules swell and take up more volume. How is the volume fraction of the starch granules in the sauce changing during this process? a. The volume fraction of the starch granules is decreasing. b. The volume fraction of the starch granules is increasing. c. The volume fraction of the starch granules is remaining constant.
b. The volume fraction of the starch granules is increasing.
Why is it easy to overcook tender meat on the grill? a. The lid of the grill traps water vapor. The water vapor is constantly condensing on the meat and steaming it. The rate of steaming can exceed 10°F a minute in a grill. Thus, it only takes a minute or two to overshoot the ideal range of temperatures. b. To be cooked but juicy, the internal temperature of meat must be heated to within a narrow range of values. However, the rate of change of the temperature can exceed 10°F a minute on a grill. Thus, it only takes a minute or two to overshoot the ideal range of temperatures. c. The collagen in meat is very sensitive to temperature. Initially it denatures which causes the meat to be juicy. However, if cooked too much, it coagulates and makes the meat tough and difficult to chew.
b. To be cooked but juicy, the internal temperature of meat must be heated to within a narrow range of values. However, the rate of change of the temperature can exceed 10°F a minute on a grill. Thus, it only takes a minute or two to overshoot the ideal range of temperatures.
A series of complex browning reactions are the Maillard reactions. What are the Maillard reactions? a. When oil molecules are heated and exposed to oxygen, they undergo a transformation. The double bond of an unsaturated fat opens up and exposes the carbon atom to reactive molecules that can break the long oil molecules into hundreds of smaller molecules which produces brown coloration and full, intense flavor. b. When carbohydrates and proteins are heated together, an unstable intermediate structure is formed. This structure then undergoes further changes, producing hundreds of different by-products. All these by-products produce brown coloration and full, intense flavor. c. When water is heated, the water molecules begin to violently jiggle and come apart. The fragments of the water molecules can then recombine into a hundreds of flavor molecules including some that produce a brown coloration. d. When sugar is heated, the sugar molecules (e.g. sucrose) melt into a syrup and then undergo chemical transformations. This results in the formation of hundreds of different reaction products such as organic acids, sweet and bitter derivatives, fragrant volatile molecules, and brown colored polymers.
b. When carbohydrates and proteins are heated together, an unstable intermediate structure is formed. This structure then undergoes further changes, producing hundreds of different by-products. All these by-products produce brown coloration and full, intense flavor.
You are trying out spherification for the first time and want to make a 'ravioli' with a gel thickness of 1 mm. You find a website that states the diffusion constant for the calcium ions is 4.2 X 10-9 m2 /s. How long should you leave your pureed pea with sodium alginate in the calcium bath? a. about 5 seconds b. about 1 minute c. about 5 minutes d. about 1 hour
b. about 1 minute
Fruit preserves are a kind of physical called a gel. The key to creating a fruit gel is pectin, long chains of several hundred sugar-like subunits. What type of food molecule is pectin? a. fat b. carbohydrate c. protein d. surfactant
b. carbohydrate
This types of protein clumps together in acid conditions and is responsible for the consistency of yogurt. a. lactose b. casein c. whey d. micelle
b. casein
Sauteing is a method of cooking food that uses a small amount of oil or fat in a shallow pan over relatively high heat. What mode of thermal energy transfer plays a dominant role in this cooking method? a. convection b. conduction c. condensation d. radiation
b. conduction
Both carbohydrates and proteins have polar regions. Water molecules are attracted to these regions and cluster around them. When they do this, they effectively surround the larger molecules and separate them from each other. If they do this more or less completely, so that each molecule is mostly surrounded by a cloud of water molecules, then that substance has______ in the water. a. dissociated b. dissolved c. dissected d. disintegrated
b. dissolved
The fat globules in milk is made up of a membrane that surrounds the globules. The membrane is composed of phospholipids and proteins. Because of this membrane, fat globules in milk are sensitive to_____but can tolerate_____ . a. heat ... freezing. b. freezing ... heat c. acids...bases. d. bases...acids.
b. freezing ... heat
Substance W is a liquid at room temperature, while Substance Y is a solid at room temperature. This suggests that the strength of the intermolecular forces between molecules of W is a. greater than the strength of the forces between molecules of Y. b. less than the strength of the forces between molecules of Y. c. equal to the strength of the forces between molecules of Y.
b. less than the strength of the forces between molecules of Y.
______ have many different chemical enviroments along its chain: parts that attract water molecules, parts that avoid water molecules, and parts that are ready to form strong bonds with similar parts of similar molecules. a. Carbohydrates b. Proteins c. Lipids d. Fats
b. proteins
As you knead dough, a gluten network forms, which increases the elasticity of the dough. This suggests ... a. the average spacing between the bonds of the network is increasing. b. the average spacing between the bonds of the network is decreasing. c. the bonds of the network are getting weaker. d. the water in the dough is evaporating leaving behind an elastic protein network.
b. the average spacing between the bonds of the network is decreasing.
A simple syrup consist of 1 cup of water (about 237 grams) and 1 and 1/2 cups of sugar (about 300 grams). The molar mass of water is 18 g/mol and the molar mass of sugar is 342 g/mol. Will the syrup contain more sugar molecules or water molecules? a. sugar b. water c. equal amounts of each
b. water
A garlic aoili is an emulsion where oil (the dispersed phased) is suspended in water (the continuous phase). To create a thick aoili sauce, what volume fraction of water is needed? a. About 0.01 or 1 % b. About 0.9 or 90 % c. About 0.2 or 20 % d. About 0.8 or 80 %
c. About 0.2 or 20 %
Two liquids are poured through a funnel. Liquid A takes longer to flow through the funnel than Liquid B even though the same volume is poured. This information tells you what about these two liquids? a. Liquid A is at a higher temperature than Liquid B. b. Liquid A is at a lower temperature than Liquid B. c. Liquid A has a larger viscosity than Liquid B. d. Liquid A has a smaller viscosity than Liquid B.
c. Liquid A has a larger viscosity than Liquid B.
Grilling and broiling are the modern, controlled versions of the oldest culinary technique, roasting over an open fire or glowing coals. In grilling, the heat source is below the food; in broiling, above. Broiling is largely a matter of what type of heat transfer? a. Conduction b. Convection c. Radiation d. Emulsion
c. Radiation
The viscosity of ketchup changes as it starts flowing from the bottle. The phenomenon is called a. Phase inversion. b. Foam collapse c. Shear thinning d. Critical volume flux
c. Shear thinning
When water undergoes a phase transition from a gas to a liquid, a large amount of energy is released. For this reason,_____ does an especially quick job of bringing the surface of the food up to the boiling point of water. a. Baking b. Broiling c. Steaming d. Microwaving
c. Steaming
What physical property determines the temperature that a material melts or boils? a. The mass of the material b. The volume of the material c. The interaction energy of the molecules in the material. d. The expiration date on the packaging of the material.
c. The interaction energy of the molecules in the material.
One of the keys to good cooking is knowing how to heat food to be the desired doneness at its center without overheating the outer regions. This is not a simple task, because different kinds of foods heat through at different rates. One of the most important variables is the thickness of the food. How long would a piece of meat that is one inch thick take to cook as compared to a half-inch piece? a. The one inch piece would take less than twice as long to cook. b. The one inch piece would take about twice as long to cook. c. The one inch piece would take more than twice as long to cook.
c. The one inch piece would take more than twice as long to cook.
In an egg, what is the ratio of water molecules to proteins? a. There are 10 water molecules for every protein. b. There are 100 water molecules for every protein. c. There are 1,000 water molecules for every protein. d. There are 10,000 water molecules for every protein.
c. There are 1,000 water molecules for every protein.
Which bag will result in more tablespoons of salt, a 1 lb bag of table salt or a 1 lb bag of kosher salt? The mass of 1 tablespoon of table salt is 19 grams The mass of 1 tablespoon of kosher salt is 16 grams a. Since both bags weigh 1 lb, there will be equal number of tablespoons from each bag of salt. b. There will be more tablespoons of table salt. c. There will be more tablespoons of kosher salt.
c. There will be more tablespoons of kosher salt.
How much energy (in joules) is needed to heat an empty oven from room temperature to a temperature of 177 °C (i.e. 350 °F)? Assume the oven has an internal capacity of 80 liters, which corresponds to about 97 grams of air inside the oven. The specific heat capacity of air is about 1.007 J/(g·°C). a. approximately 11,000 J b. approximately 13,000 J c. approximately 15,000 J d. approximately 17,000 J
c. approximately 15,000 J
A twizzler is stretched by pulling on both ends. When the twizzler is no longer being pulled, it slowly returns to its initial length. The deformation that occurred was ... a. plastic b. entropic c. elastic d. thermo-reversible
c. elastic
Mayonnaise is a type of dispersion called an emulsion. What substance makes up a majority of the dispersed phase of mayonnaise? a. water b. air c. oil d. egg whites
c. oil
Pectin is a polysaccharide (made from a variety of sugars, including galactose, xylose, arabinose) that play a critical role in creating the right consistence in jams. When fruit is cut up and heated near the boil, the pectin chain are shaken loose. However, upon cooling, they do not re-form a gel partly because ... a. pectin molecules decompose into smaller molecules (sugars) as soon as they dissolve into the water. b. pectin molecules are extremely volatile and evaporate at a very low temperature. c. pectin molecules in water accumulate negative electrical charge and repel each other.
c. pectin molecules in water accumulate negative electrical charge and repel each other.
After whipping egg whites, you notice the volume increases by a factor of 5 from the initial volume of 1 cup to 5 cups. Therefore, you surmise that 4 cups of air have been incorporated into the foam. What is the volume fraction of the air in the foam? a. 0.5 b. 0.64 c. 0.7 d. 0.8
d. 0.8
E. coli divide every 20 minutes. At 9 am during food preparation, cross contamination leads to a piece of spinach with E. coli on it. How many times will it divide before it is served on a salad for lunch at 1 pm? a. 3 times b. 6 times c. 9 times d. 12 times
d. 12 times
A typical yogurt culture has a doubling time of about 30 minutes at approximately 105 °F. If the yogurt is held at this temperature for 4 hours and there were initially 1 million bacteria, how many bacteria are there now? a. about 1 million b. 8 million c. 128 million d. 256 million
d. 256 million
The plot below represents data collected from food being heated. What would the time constant be for this temperature change? a. 30 °F b. 300 °F c. 40 minutes d. 90 minutes
d. 90 minutes
Why will a cast iron pan absorb more heat and hold it longer than aluminum? a. Cast iron is an excellent conductor of heat and less dense than aluminum. b. Cast iron is a poor conductor of heat and much less dense than aluminum. c. Cast iron is a excellent conductor of heat and much denser than aluminum. d. Cast iron is a poor conductor of heat and much denser than aluminum.
d. Cast iron is a poor conductor of heat and much denser than aluminum.
A microorganism uses what type of protein to break larger molecules into smaller molecules? a. Carbohydrates b. Alginates c. Triglycerides d. Enzymes
d. Enzymes
Inadequate or excessive salt concentration, or temperatures, or exposure to the air lead to what problem in vegetable fermentation? a. Growth of lactic acid bacteria b. The conversion of sugars into acids, carbon dioxide, and/or alcohol. c. Preservation of the vegetable in a brine or acid. d. Growth of undesirable microbes.
d. Growth of undesirable microbes.
Lecithin is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues composed (wikipedia). In class, we discussed the using the lecithin in eggs as an emulsifier. Why is lecithin a good emulsifier? a. Lecithin is also found in olive oil and bonds with oil droplets. b. Lecithin has an abundance of hydrogen atoms. c. It is very long and straight. d. It's molecular form has a hydrophobic end and a hydrophilic end.
d. It's molecular form has a hydrophobic end and a hydrophilic end.
Lactose intolerance is a condition in which people have symptoms due to the decreased ability to digest lactose, a sugar found in milk. What is the cause of lactose intolerance? a. Lactose intolerance is due to not enough of the milk sugar lactose to break down the enzyme lactase found in milk. b. Lactose intolerance is due to the volume fraction of the milk fat triglyceride being below the critical volume fraction. c. Lactose intolerance is due to the volume fraction of the milk fat triglyceride being above the critical volume fraction. d. Lactose intolerance is due to not enough of the enzyme lactase to break down the milk sugar lactose.
d. Lactose intolerance is due to not enough of the enzyme lactase to break down the milk sugar lactose.
What type of basic food molecule is collagen? a. water b. Lipids (fats and oils) c. Carbohydrates d. Proteins e. None of the above
d. Proteins
____ is understood to be a manifestation of starch retrogradation which is the recrystallation of the starch granuales as the water migrates out of the granules. a. Melting b. Tempering c. Rising d. Staling
d. Staling
The final consistency of a tomato puree depends not just on how much water has been removed, but also on how long the puree spends at either moderate or high temperatures. Ripe tomatoes have very active enzymes whose job is to break down pectin and cellulose molecules in the fruit cell walls, and so give the fruit its soft, fragile texture. When tomatoes are first crushed, the enzymes and their target molecules are thoroughly mixed together and the enzymes start breaking down the cell-wall structures. If a raw tomato puree is cooked quickly close to the boil, the result is a thicker sauce as compared to slowly letting the temperature rise. Why? a. At the boil, the enzymes swell with water and take up more space. Since the volume fraction of enzymes increases, the viscosity of the puree also increases. b. At high temperatures, the enzymes form bonds between the lipid bilayer in the cell membrane. These bonds cause the cells to form structures called 'cell rafts' which take up a lot of space and cause the puree to thicken. c. The pectin and cellulose enzymes become very active at the boil. The enzymes will break down a lot of the cell-wall reinforcements, and these liberated molecules will give rise to a noticeably thicker consistency to the puree. d. The pectin and cellulose enzymes are denatured and become inactive, while at the same time the cell walls are disrupted by the heat. The cell-wall pectin that escape into the fluid phase during the concentration heating are longer molecules and more efficient thickeners as compared with molecules that were partly broken down by the enzymes.
d. The pectin and cellulose enzymes are denatured and become inactive, while at the same time the cell walls are disrupted by the heat. The cell-wall pectin that escape into the fluid phase during the concentration heating are longer molecules and more efficient thickeners as compared with molecules that were partly broken down by the enzymes.
A potato is cooked using two different methods: method #1 and method #2. For both methods, the temperature of the food follows the following expression ... T(t)= (T food- T external) e^-t/T +Texternal However, for method #1, 1 is a larger value. In the kitchen, what would be the apparent difference between the two methods? a. The potato prepared using method #1 would reach a higher temperature when cooked for a long time. b. The potato prepared using method #2 would reach a higher temperature when cooked for a long time. c. The potato prepared using method #1 would cook faster. d. The potato prepared using method #2 would cook faster.
d. The potato prepared using method #2 would cook faster.
How will tripling the thickness (i.e. depth) of the lasagna affect the cooking time? For example, cooking a lasagna that is 6 inches thick rather than 2 inches. a. Tripling the thickness will triple the cooking time. b. Tripling the thickness will not affect the cooking time. c. Tripling the thickness will reduce the cooking time by a third. d. Tripling the thickness will increase the cooking time by a factor of 9.
d. Tripling the thickness will increase the cooking time by a factor of 9.
What critical role does yeast play in bread making? a. Yeast attack microbes that spoil dough and prevent it from rising. b. Yeast convert sugars into flavor molecules that are then used in the Maillard reaction. c. Yeast convert sugars into gluten that serves as the elastic structure in dough. d. Yeast convert sugars into carbon dioxide that help to inflate dough.
d. Yeast convert sugars into carbon dioxide that help to inflate dough.
A microorganism in kimchi divided 30 times over the course of fermentation. If there was just one microorganism to start with, how many are there after 30 divisions? a. about 1 million b. about 10 million c. about 100 million d. about 1 billion e. much more than 1 billion
d. about 1 billion
Ingredients for a Hershey's cup of hot chocolate for one: 2 tablespoons sugar 2.5 teaspoons Hershey's Cocoa Dash salt 1 cup milk 1/4 teaspoon vanilla extract To scale this recipe to serve 20 people, how much Hershey's Cocoa would you need? Please refer to the equation sheet if conversions are needed. a. about a 1/4 cup b. about a 1/3 cup c. about a 1/2 cup d. about 1 cup
d. about 1 cup
How much energy (in joules) is needed to heat a cup of water from room room temperature to a temperature of 93 °C (i.e. 200 °F)? Assume the mass of the water is 300 grams. The specific heat capacity of water is about 4.18 J/(g·°C). a. approximately 90 J b. approximately 900 J c. approximately 9,000 J d. approximately 90,000 J
d. approximately 90,000 J
Proteins can unfold. This change involves breaking the bonds that maintain the molecule's folded shape and undoing its natural structure. It is important to note that this change is not a change in composition, but a change in structure. This process is called ______. a. coagulation b. dissolving c. sublimation d. denaturation
d. denaturation
There's a particular group of proteins that are important to the cook not so much for their direct contribution to the food texture and consistency, but for the way they change the other components of the food they are in. These proteins ae biological catalysts that increase the rate of specific chemical reactions that would otherwise occur very slowly. These proteins are called______. a. DNA b. hormones c. cryptochrome d. enzymes
d. enzymes
In the expression ... T(t)= (T food- T external) e^-t/T +Texternal what does T in -t/T physically represent? a. initial temperature of food b. final temperature of food c. temperature of the environment d. the time it takes to heat the food a little past half of its final temperature
d. the time it takes to heat the food a little past half of its final temperature
