Name ______Period _____ Days______Date ______
The Biochemistry of Milk
The Complex Nature of Milk
Vital to health - nutritious
Versatile for cooking – 87% ______(a solvent for over 250 chemical compounds, the milk sugar lactose, water-soluble vitamins, trace minerals and mineral salts)
Milk is a ______, a ______, and an ______
Proteins
80% of milk protein is ______
Casein molecules associate with each other in tiny, raspberry-like structures called ______– an aggregation, or cluster of molecules often found in colloidal dispersions
As long as milk keeps its normal acidity, level (pH - 6.6), casein remains stable…if an acid is added, the casein ______to form ______. When cooking, you can prevent curdling by using ______ to thicken the milk. The starch surrounds the casein and prevents coagulation.
20% of milk protein is ______
Whey is the ______found in the ______ that remains after fat and casein have been removed from milk
Whey is also called ______protein. Heat will easily coagulate whey, although heat has little effect on coagulating casein.
In addition to the proteins, casein and whey, milk contains a number of ______that are also protein molecules. Most of these are ______during pasteurization.
Another way to coagulate milk is with the enzyme rennin, which is used to clot milk in the first stage of cheese making.
Fats
Milk is an ______ because small globules of ______are dispersed throughout the water. Around each fat globule is a thin membrane containing proteins, phospholipids and bound water, suspending clusters of fat in droplets.
______ – fat droplets form larger clusters that rise and float to the top.
Cream is milk that is extra rich in emulsified fat droplets
The fats in cow’s milk are the most complex lipids known. The lipids include over 400 different fatty acids.
Milk fat contains very little ______ compared to egg yolk.
The fats in milk influence the flavor, texture and price – the ______fat, the ______ the price.
Carbohydrate
Milk sugar – ______
______– enzyme that breaks lactose into glucose and galactose
______– no lactase in intestines – lactose remains undigested, then certain intestinal bacteria attack and ferment the lactose, producing acids and gas – this causes discomfort
______milk products (yogurt, buttermilk)
Vitamins and Minerals
Minerals – in the form of salts – chlorides, phosphates, citrates of potassium, ______, sodium, and magnesium (salts prevent milk from curdling)
Trace ______ – cobalt, copper, iodine, iron, magnesium, nickel, molybdenum
Vitamins:
______ – breaks down when exposed to light – this is why milk cartons are opaque
Thiamin
Niacin
Vitamin A
Processing Milk
______ – heated to a high temperature for a short time – destroys ______bacteria
______ – eliminates creaming – under pressure, milk is forced through small openings to break down fat and keep the fat molecules permanently separated
______ – Vitamin D is added (helps the body absorb calcium and phosphorus), and Vitamin A (a fat-soluble vitamin) is added back to low-fat milk products (by law)
Types of Milk Products
______ milk
______ – in sealed box – long shelf-life (3 months or more if unopened)
Concentrated milk – ______– ______ is added to stabilize the casein – off white color is caused by chemical reaction of lactose and amino acids
______ – 50% of water is removed, 44% sugar is added – used in dessert recipes
______
Half and Half – 10.5% to 18% fat
______cream or Coffee cream – 18% to 30% fat
______cream – 30% to 36% fat
______cream – at least 36% fat
Whipping cream is often UHT pasteurized to lengthen shelf life
______ – dried into powder form – milk solids can be reconstituted by adding water
Non-fat dry milk has longer shelf life – no fat to oxidize and spoil the product
______ milk products
______ – buttermilk, yogurt, cheese
Process – pasteurized, lactic-acid bacteria breaks down lactose (lowers the pH), ______(starter is added), ______, ______
Cheese
Made by ______the ______protein
______– aged – makes the flavor and texture distinct
Moisture content varies
______– Parmesan, Romano
______– Cheddar, Colby, provolone
______– Muenster, Roquefort
______– Brie, Camembert, mozzarella
______– cottage cheese, cream cheese, mozzarella
Storing Milk Products
Keep it ______!!
Use closed, ______containers – ______is light-sensitive
______cans or UHT boxes after opening
Store non-fat dry milk at room temperature – keep moisture out
Keep cheese cold, although it tastes better when served at room temperature – wrap carefully to keep it from drying out
Cooking with Milk
Making ______
More fat = higher ______(thickness) = better whipped cream
Cold temperatures increase viscosity – whip cream when it’s ______!! Use cold mixing bowls and beaters
Whip small amounts
Adding sugar decreases the volume and stiffness of the foam, so add sugar after whipping the desired amount of air into the foam
______Milk
Milk ______– it’s highly sensitive and highly reactive to heat – heat denatures and coagulates the whey proteins of fresh milk, causing them to precipitate, then it settles to the bottom, and scorches – use a ______to prevent this
When heated till scalding in open containers, evaporation causes a ______to form on top (marshmallow or whipped cream prevents this)
______can occur at high temperatures – use low temperatures and non-acid ingredients to prevent this
______action
Some desserts use rennet to make clotted milk - use moderate temperatures so enzyme is not inactivated
______
Causes milk to curdle (like when you add fruit to your milk and cereal or lemon juice to tea and milk)