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4-3 Milk

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by

Kristin Shapiro

on 5 February 2013

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Transcript of 4-3 Milk

Biochemistry of Milk Milk is a emulsion (therefore also a colloid & solution) unit 4-3 Milk Contains:
Mostly water
Protein
Fat
Vitamins & minerals
Carbohydrates 2 main proteins in milk: Casein: in a structure called micelles
Stable at pH of 6.6
Changes to pH cause casein to break down: forms lumps (curds) Whey: Protein found after fat & casein had been removed
easily coagulated by heat Fat in milk small globules of fat are dispersed in milk (is an emulsion)

Each globule has a thin membrane that surrounds it and keeps it separated from the others

Membrane is made of proteins, phospholipids and water. cream is milk that is extra rich in fat and floats to the top of freshly drawn milk (creaming) Size of globule depends on the animal producing the milk
Fat influences flavor, texture, and price. More fat = more $$$$ Carbohydrates in Milk lactose is main sugar Under heat, amino acids within the protein react, producing a slightly caramel flavor Lactose



galactose & glucose


these are used by body for fermentation during digestion by lactase Lactose: from cells of lactating mammary gland
Adds body to milk & sweet taste Lactose intolerance: inability to digest milk due to lack of amylase. Lactose that remains undigested gets fermented by bacteria in the intestine Minerals & Vitamins in milk Most of the minerals present are in the form of salt.

Trace elements include cobalt, copper, iodine, iron, magnesium, nickel and molybednum… depends on soil of cows feed.

Vitamin Riboflavin is present in highest amount. Gives off green tint in fat free milk. Other vitamins include thiamin, niacin, and Vit A Salt keeps milk from curdling by stabilizing the casein micelles.

Acids remove calcium ions, causing curdling. Pasteurization
Homogenization
Fortification Processing Milk pasteurization Milk is heated to high temperatures for a short period of time to destroy bacteria.
Denatures enzymes that cause milk to spoil
Small effect on nutritional value. homogenization Process used to eliminate creaming.
Under pressure of 2,000 to 2,500 pounds per square inch, milk is forced through small opening in a machine called a homogenizer.
Fat particles are broken down and surrounded by an emulsifier that keeps them permanently separated. fortification Most milk producers fortify milk with vitamin D (helps your body absorb & use calcium and phosphorus)

Process: Milk is exposed to ultraviolet light, which converts some of the milk fat components to Vit D.

When fat is removed to make low fat varieties, most of the vit A is removed. By law, vit A has to be added back when removed. The addition of a nutrient to a food. Ultrahigh-Temperature Milk
Concentrated Milk
Cream
Dry Milk
Cultured milk products:
Buttermilk *
Sour Cream*
Yogurt*
Cheese* Types of Milk Products Whole milk heated at low pressure causing 60% of water present to evaporate at temp. way below milks normal boiling point.

Carrageenan is added to stabilize casein proteins Sweetened Condensed Milk Evaporated Milk Concentrated Milk 50% of water has been removed and sugar is added.

44% sugar

Milk does not need sterilization because sugar acts as preservative. Cream Half and half- 10.5- 18% fat

Light cream/ coffee cream- 18 -30% fat

Light whipping cream 30-36% fat

Heavy whipping cream 36+% fat Dry Milk Milk is pasteurized and then water is removed leaving milk solids

Nonfat has a longer shelf life that whole or low fat because it has been dried longer

Can be returned to its liquid form by mixing it with water.

Sometimes added to casseroles to enrich. Cultured Milk Products Cultured is the term for any milk product that has been fermented to produce a distinct flavor or texture.

A culture is a controlled bacterial population added to milk.

Steps:
Pasteurize milk
Add lactic acid to break down lactose and creates low pH
Inoculation takes place (starter added)
Incubation period- give time to ferment
Cooled to stop or slow fermenting. Buttermilk Originally fluid left over from production of butter.

Today cultured product from skim or low-fat milk. Also sold in powder for baking. Sour Cream Culture added to cream to make sour cream.

Held at certain temperatures until proper acidity is reached.

Doesn’t have sour taste…

Lower in fat that salad dressings, good for dips and sides Stretococcus lactis Yogurt Contains lactose, lactic acid, B vitamins, and protein… low in calories

Prepared by adding bacterial culture to milk that has been heated.

Gelatin or vegetable gum often added to guarantee firmness and body… or they can add more milk solids. cheese Made by coagulating the casein protein in milk.

Once curds form, whey is drained away.

Heating and cutting the curd helps drainage.

Curd is then treated

Most cheeses are then given time to age or ripen. Ripening cheese Creates a physical and chemical change in the cheese.

Held in a temperature and humidity controlled environment for at least 60 days.

Producers create flavors by controlling enzymes & other factors

Classified as strong, sharp or mild. Moisture content 4 categories of cheese are based on moisture content.
Very hard cheeses- parmesean, romano
Hard cheeses- cheddar, colby & provalone
Semisoft cheeses- muenster, roquefort, and stilton
Soft cheeses- brie, cambert, & mozzarella


Unrippened- high moisture content- cottage, cream, mozzarella Making foams
Heating milk Cooking with Milk foams Fat content- the higher the fat, the better the foam

Temperature- cold temperatures increase viscosity. Below 7˚C is best

Amount- using small amounts gives better results than whipping large amounts.

Sugar content- sugar decreases volume and stiffness of foam, while increasing the time it takes the foam to form. Add sugar after cream has reached desired consistency. Heating milk Milk is sensitive and highly reactive to heat.

Milk should be cooked over low heat or in double boiler to prevent scorching. Ultra-high temperature milk (UHT) With special processing, milk can be stored without refrigeration for three months or more if unopened.
Prepared by heating for a short period of time at Ultra High Temperatures.
Placed in specially sealed packaging that keeps spoiling bacteria out.
Flavor not real good right after processing, but improves with time…unless stored for too long!!!
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