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Food Science Quiz
Milk, Cheese, and Eggs
| Question | Answer |
|---|---|
| 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
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