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Teacher Preparation


Learning Goal

Upon completion of this lesson participants will be able to understand and describe milk processing steps.

 

Resources & Materials


Lesson Delivery

 

Anticipatory Set

  • As you may know, processing of food products is vital to increase shelf life, increase food safety, and ensure food safety and quality for consumption.
  • Today we hope to guide you through the processing steps that dairy products go through before they reach your table.

 

Direct Instruction

1st Learning Goal: Upon completion of this lesson participants will be able to understand and describe milk processing steps.

 

Content Outline

At the Dairy

  • Dairy cows, like our Holsteins, can produce up to ten gallons of milk a day.
  • Most dairies milk their cows 2-3 times a day, to empty their udders and keep the cows comfortable.
  • The milk at the farm is called raw milk because it hasn’t been processed for human consumption yet.
  • As the cows are milked, the milk is immediately cooled through tubing and bulk tanks.
    • Bulk milk tanks will cool milk from about 101* F to 34-36* F in a short period of time and will maintain that temperature until the milk leaves the farm.
    • An agitator in the bulk tank mixes the milk periodically to maintain even temperature throughout.
    • The milk is never exposed to outside air or airborne contaminants.

Leaving the Dairy

  • Every day or two, milk is taken from the dairy in an insulated tanker truck to a dairy processing plant. Within the tanker the milk is kept at 38 degrees.
    • The tanker holds approximately 6000 gallons of milk and is always cleaned and sanitized before milk is loaded.
  • The hauler checks the milk to make sure it meets certain standards of freshness and collects several samples from each farm milk tank.
  • Once the milk arrives at the processing plant it is tested again before being unloaded.

Processing the Milk

  • Milk is transported to one of several processing plants that manufacture products like cheese, ice cream, milk, yogurt, butter, or milk powder.
  • The milk samples are tested at a laboratory by lab technicians to make sure the milk is safe and fresh to be processed for us to drink.
    • One sample is immediately checked for temperature. If the temperature of the milk is above 40°F, the entire load is discarded.
    • Another sample is tested for bacteria and antibiotics. In the rare event that the tanker of milk tests positive, the entire load is discarded.
    • Milk is never unloaded until it passes all tests.
    • The technician also tests the butterfat content. Butterfat is also called cream.
  • When milk passes “inspection,” processing begins.
  • Once the tank truck driver gets the okay from the lab, the pumping begins.
    • Milk is pumped into large, refrigerated storage tanks or silos.
  • One of the first stops is the separator.

The Separator

  • Milk is pumped into a separator that spins the milk to separate cream, which is lighter, from the skim.
  • The desired amount of cream can then be added back to the skim later to obtain milk standard for 1%, 2%, or whole milk which is 3.25% fat. Excess cream can then be used to make ice cream and butter.
  • Some of the milk is even pumped to mixing tanks. Here other ingredients are added to make flavored milk.

The Homogenizer

  • The milk is pumped into a homogenizer that breaks up the fat globules and makes them smaller.
    • Milk is forced through very small holes under great pressure.
    • This breaks the butterfat particles into tiny, uniform pieces.
    • A protein coat surrounds each butterfat piece. This keeps the butterfat from clumping back together.
  • This makes the milk have consistent flavor when bottled.
  • If milk were not homogenized, the cream would rise to the top. You would have the shake or stir the milk before drinking it.

Pasteurization

  • In 1865, a French scientist named Louis Pasteur discovered that heating liquids to high temperatures kills microorganisms.
  • Milk is pasteurized which kills bacteria that may be harmful to health.
    • Heating milk to 165* F for 15 seconds then quickly cooling it down to 35* F accomplishes this.
  • Pasteurization protects the purity and flavor of milk without influencing the nutrient value.

Preparing Milk for You

  • Milk is always bottled in sterile containers that are fed down a conveyor belt to the filling station.
  • Containers (bottles or cartons, in some countries they even use plastic bags) are automatically filled with the proper amount of milk, sealed and capped.
  • Milk is stored in a refrigerated room that is kept at 36 degrees until it is ready to be transported to grocery stores or schools.
  • Refrigerated trucks are used to deliver bottled milk to its retail destination.
  • It takes only about two days from the time milk leaves the cow until it reaches the grocery store.
  • Still, some milk doesn’t get bottled for drinking, instead it’s set aside for further processing to make ice cream, cheese, yogurt, butter, or other dairy products.

Milk is Safe

  • Milk is one of the safest food/drinks you can consume:
    • Human hands never touch the milk.
    • The milk is tested to make sure it is fresh and clean.
    • Milk is always kept cold as it travels from the cow to dairy processing plant and finally to the store or school.
    • These steps are important to make sure that milk is always safe and fresh for us to drink.

Learning Activity

Adults should be provided with the option to take an informational handout that covers basics about the dairy, how to schedule tours, and animal science department contact information.

 

Closing Announcements/Reminders

  • Answer any questions they may have
  • Thank them for coming to the Ferguson Family Dairy
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