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Food Science Quiz

Milk, Cheese, and Eggs

Percent of fat in fluid whole fluid milk 3.25%
Percent of fat in 2%, 1% and skim milk less than 0.5%
Percent of fat in half and half 10-12%
Percent of fat in cream 30-36%
Percent of fat in heavy whipping cream 36-40%
Percent of fat in butter 80%
Fermented, pasteurized milk, heated and cultured is: yogurt
Light cream cultured as yogurt is: sour cream
Remaining milk after churning butter; skim milk buttermilk
Soured milk produced by culturing buttermilk to convert lactose to lactic acid cultured buttermilk
Functions (2) of fat globules: 1. flavor 2. viscosity (thickness)
This is when whole milk stands and fat globules rise to the top (separate) Creaming
What prevents creaming? homogenization
Milk forced under pressure through fine orifices (small screen) that decrease fat globule size Homogenization
Adsorbed means: (such as casein proteins are adsorbed to fat dropplets and causes greater density to visible creaming does not occur again) attract and hold to the surface
Homogenized milk looks: more white, more opaque, and more viscous
Mild heat treatment that eliminates pathogens and some enzymes Pasteurization
This process destroys lipase so milk will not become rancid Pasteurization
80% of milk proteins are: caseins
20% of milk proteins whey
What in milk keeps the micelles colloidally dispersed? Their negative charge on their surface
What is the effect of heat on casein? no effect
What is the effect of heat on whey? denatures the protein
What is the effect of acid on casein? Causes the protein to reach its isoelectric point of 4.6 and it precipitates
What is the effect of acid on whey? no effect
What is the isoelectric point? the pH at which the protein is least soluble and there is no net charge on the amino acid (neutral state)
What is the pI for casein? 4.6
Where is the calcium displaced when milk is exposed to acid? in the whey (acid does not affect whey proteins)
Where is the calcium displaced when milk is exposed to rennin? micelle
What is a foam? an air-in-liquid dispersion, usually stabilized by protein
What is the difference between evaporated milk and sweetened/condensed milk? evap. milk gets rid of 60% water condensed loses 50% and 44% sugar is added
Cheese is: a curd of milk and a gel of casein (liquid trapped in a solid)
What is cheese made up of? water, protein, fat, Ca, P, vitamin A, carotenoid pigments
What is unripened cheese? Eaten same day its made or soon after
What is ripened cheese? let sit to age; ate long time after its made
What are the two types of unripened cheese? high moisture (soft-cream cheese) and low moisture (firm- mozzarella)
What are the four categories of ripened cheeses? Soft, semisoft, firm and very hard
Soft ripened is: 50% moisture
Semisoft ripened is: 35-45% moisture
Firm ripened is: swiss, gouda, cheddar
very hard ripened is: Parmesan, romano
What are the four steps in cheese production? 1. coagualte casein 2. separate curds and whey 3. add salt, color, microbes, etc. 4. Ripen (age/time)
What are two ways you can add acid in cheese production? 1. add acid 2. use bacteria that converts lactose to lactic acid
Where is rennin commonly found? from calf stomachs -- today from microbes!
Describe rennin: chymosin enzyme, protease that splits casein mycelle at k-casein (hydrophilic outside)
What are processed cheeses made of? shredded natural cheese and an emulsifier (blended and pasteurized)
What enhances as cheese ages? flavor (from over 400 compounds--hydrolysis of fat, beta-casein, lactose/lactic acid, citrates, proteins)
What is lacking in processed cheeses? flavor (because of presence of water and emulsifiers which dilute flavor)
At what temperature does fat melt/separate and cheese melt? 90 degrees C or greater (not good to go over 90C)
At what temperature do proteins denature, coagulate? 140 degrees C (cheese shrinks and toughens)
More ripened cheeses: blend better, can tolerate higher temperatures
Processed cheeses: blend rapidly and make smooth but adhesive sauces, lack flavor, best for blending (emulsifiers)
Cheese blends better liquids with these characteristics: more ripening, moisture, fat and emulsifiers.
Cheese in liquid is more grainy when: it is less ripe, has less moisture, less fat, and less/no emulsifiers
Name an unripened soft cheese Cottage cheese, cream cheese
Name a ripened very hard cheese Parmesan, Romano
What are some cheese variables? microbes, aging time, temp, humidity, acid/rennin added, type of milk, and percent of salt
How much does a standard large egg weigh in grams? 50 g
Why are eggs so important? They hold the highest quality protein of any food and they are affordable!
What is the composition of an egg? 75% water, 13% protein, 11% fat, 1% minerals
What is the egg white (albumen) composed of? protein and water (no fat!)
Draw an egg Include: Albumen (white) Shell membranes (2) Chalazae Yolk Germ Shell (calcium carbonate) Air Cell
What makes up the shell of an egg? Calcium carbonate crystals
What is special about the shell of an egg? It is porous but only allows air to pass through and is impervious to bacteria and other molecules
As the egg ages what happens? The air cell increases in size
What is the egg yolk composed of? 1/2 water, 1/3 lipid, 1/5 protein (lots of fat and cholesterol)
What does the protein Ovotransferrin do? binds iron and copper
What does Ovomucoid have? small amounts of glucose
What are globulins needed for? foaming
What does lysozyme do? kill bacteria
What does Ovomucin do? contributes to the thickness of the egg white
What does Avidin do? binds biotin to protect against microbes, this protein can be denatured by cooking
The white of an egg coagulates at a wide range of temperatures, why? because it is composed of several proteins that have different coagulation temperatures
What are the two types of egg yolk lipoproteins? low density and high density
What proteins are present in the egg yolk? low density and high density lipoproteins, cholesterol, lecithin, Lipovitellin, Phosvitin, Livetin, LD lipoproteins (phospholipids, cholesterol, TG, proteins)
What are the six sizes of eggs? Jumbo, Extra large, Large, Medium, Small, Pee Wee
What sized egg is standard for recipes if not mentioned in the recipe? large eggs
What egg is the best economically? Jumbo
The size of the egg depends on what? The hens age
What are the three levels of egg quality? AA, A, B
What are some methods to check egg quality? candling and break-out test
What are the requirements for a Grade AA egg? Shell-clean and unbroken, air cell small and centered, yolk centered and tall, white thick and clear
Fresh eggs have what characteristics? clean unbroken shell, tall yolk (centered), thick white, strong membranes, ph 7.6, small air cell
Old eggs have what characteristics? Short, off-centered yolk, weak memebranes, spreading white, large air cell, ph 9.0 (rises as it ages)
The date on the egg carton is called what? Julian Date
What does refrigeration have an effect on during egg storage? Slows moisture loss and CO2 loss
What part of an egg freezes well? white
Eggs can last how many weeks in the fridge? 8-12 weeks
Conalbumin is another word for? Ovalbumin
How are eggs resistant to spoilage? Shell and inner membranes act as lines of defense, egg white contains antibacterial agents (lysozyme, avidin, conalbumin)
What common pathogen is found in eggs? Salmonella enteritidis
What other pathogen can be associated with eggs, but rarely? Listeria monocytogenes
What are some functions of eggs in food? color and flavor, emulsifying agent, thicken, bind, structure/texture, foams
What are the effects of heat on egg proteins? denaturation, coagulation (protein-protein interactions--new bonding), gelation (protein-solvent interactions--alters conformation as well)
At what temperature range does egg white denature? 60-65 degrees C
At what temperature range does egg yolk denature? 65-70 degrees C
What factors other than heat influence coagulation? pH of dispersion, presence of salts, how fast the temp rises (cook faster increases coagulation)
Created by: rkcarlon