Lecture 15: Milk, Dairy, and Cheese Flashcards
Kumiss
Commonly produced in Russia from raw mare’s milk
Kefir
- Milky beverage fermented from cows by Balkans
- Commonly produced in Southwest Asia
- Basically watered down flavored yogurt
What is the Greek word for “milk drinkers”?
Galaktopotes
When did the colonists introduce dairying to America?
1625
By what year did dairying become a modern industry?
1850
What is milk?
A white, opaque fluid of female mammals for the total sustenance of their offspring
Colostrum
- First fluid secreted by the mammary glands of female mammals
- Clear solution of concentrated protein, vitamins, and antibodies
What factors affect how milk’s composition varies?
- Species of cow (size, genetics)
- Region, climate, season
- Type of feed
- Care for animals
Common dairy breeds
- Holstein
- Brown Swiss
- Guemsey
- Jersey
What are the 2 types of milk proteins?
- Caseins
- Whey proteins
What determines the type of milk protein?
Their reaction with acid or chymosin (rennin)
What do caseins form?
Curds, clumps
What are micelles formed from?
Casein and minerals (phosphate, calcium) in milk
What causes casein particles to clump/curdle?
Chymosin or acid
How is cream made? (2 ways to do this)
Separation of fat globules from the water phase
- fat globules rise b/c it’s less dense than water
- separated by centrifuge
Who developed pasteurization?
Louis Pasteur
Why was pasteurization first developed?
To prevent wine and beer from spoiling
Difference between pasteurization and sterilization
- Pasteurization reduces number of microorganisms, but doesn’t kill them all
- Sterilization kills all microorganisms
What are the 2 time/temp combos for milk to be pasteurized?
- 144 F for 30 mins
- 160 F for a few secs
HTST
High Temp Short Time pasteurization (160 F for a few secs)
UHT
Ultra High Temp pasteurization
- doesn’t sterilize milk product, but drastically reduces # of microorganisms
- extends shelf life
- gives milk product cooked lavor
What does homogenization do to milk?
Breaks down the fat globules to prevent them from rising to form a separate layer of cream on the top
How is milk homogenized
Milk is forced through a small nozzle onto a hard surface
How much fat does whole milk have?
4%
Why does milk have to be fortified?
When fat is removed, other lipids including fat-soluble vitamins go with it
What does fortification add to milk?
Fat-soluble vitamins A & D
What are the modern concerns surrounding milk products?
- Use of antibiotics
- Use of hormones
What causes cream to be whipped?
- Foam of air in water
- Proteins stabilize the air bubbles
- Fat increases the viscosity of the liquid
What happens if the cream is whipped past the stiff phase?
- Phase reversal to butter
- Butter squeezes out all the water –> produces butter and buttermilk
Churning butter
Churning breaks the bubble structures and collapses the fat globules together to form butter and the liquid residue (buttermilk)
What makes butter yellow?
Natural vitamin A
Why is butter packaged in aluminum?
Keeps the light out –> light causes rancidity
What affects the quality of butter?
Ratio of amorphous (free) fat to crystallized fat
Tempering
Process of using different temps to ensure different kinds of crystals form in food
-important for texture
Why is salt added to butter?
- Preservative
- Enhances taste
What percentage of butter is the liquid water portion?
16%
What part of the butter becomes rancid? Why?
Liquid water portion can harbor bacteria and start turning rancid
What is the original origin and purpose of margarine?
-Goal was to produce a food easy to carry that provided a lot of calories for Napoleon’s armies
Today, how is margarine made?
- Made of hydrogenated (partially saturated) vegetable oils
- Emulsified with cultured skim milk
- Flavored and colored
What is a concern surrounding margarine?
Trans fats
Fats vs. Oils
- Oils = unsaturated fatty acids; liquid at room temp
- Fats = saturated fatty acids; solid at room temp
Through what process is vegetable oil converted to margarine?
Catalytic hydrogenation
How does catalytic hydrogenation convert vegetable oil to margarine?
Saturates some of the double bonds –> partial hydrogenation
Downside of catalytic hydrogenation
Converts cis-unsaturations to trans-double bonds –> TRANS FAT
In essence, what is ice cream?
A foam stabilized by freezing the liquid phase
4 component phases of ice cream
- Liquid containing sugar, protein, salts
- Ice crystals
- Fat globules
- Air cells
What is undesirable when making ice cream?
Lactose crystals
What does the law require for a food to be labeled “ice cream”?
- 10% milk fat
- 20% total milk solids
- <4.5 lbs per gallon (weight)
What are major factors that determine quality and price of ice cream?
Fat and air content
Standard of Identity
Code of Federal Regulations spells out exactly what standards a product must have to be labeled a certain food name
Creaming
Process of removing milk fat, usually via a centrifuge
What milk products are fermented?
All curdled milk products
How does fermentation prevent/retard undesirable spoilage and pathogens?
- Producing acid
- Competing for nutrients
Starter culture
Bacterial agent added to milk to assure a good fermentation
Probiotic
Live strains of good bacteria that help our digestive system work efficiently
Prebiotic
Nutrients bacteria feed on to increase their numbers
Synbiotic
Products are both probiotic and prebiotic
Acidophilus milk
- Fermentation replaces some lactose with lactic acid –> sour taste
- Lactose intolerant peeps can drink it b/c less lactose than regular milk
How is today’s buttermilk made?
Not drawn off butter churn, but cultured low-fat or skim milk
What is yogurt made from?
Whole or skim milk plus dried milk solids
Who popularized yogurt?
Elie Metchnicoff
How was cheese discovered?
- When the fourth stomach of a milk-fed calf was used as a vessel for carrying milk
- Stomach contained rennet
- Rennet causes solids to separate from liquids in milk
Rennet
An extract of milk-fed calves’ fourth stomach
Cheddaring
Curds cut into blocks and piled up
How are cheeses prepared for ripening?
Surface is often coated with waxes or other materials to protect the cheese within
“Green” cheeses
Unripened cheese
What determines the hardness of cheeses?
Water content
For ice cream, the term “overrun” refers to ___?
Air content
