Dairy Technology II SS3 Livestock Farming Lesson Note

Why Process Milk?

Fresh milk is like a ticking clock; it spoils very quickly. Processing is our way of “stopping the clock.” By turning milk into yoghurt, cheese, or butter, we:

1. Make it last longer (Preservation).
2. Make it taste different (Variety).
3. Make more money (Value Addition). A cup of yoghurt often sells for much more than a cup of raw milk!

Making Yoghurt (The Power of “Friendly” Bacteria)

Yoghurt is made by “fermenting” milk. We use heat and specific bacteria to turn the milk sugar (lactose) into acid.

The Simple Steps:

• Pasteurization: Heat the milk to about 85°C for 30 minutes. This kills any “bad” bacteria that might be hiding inside.
• Cooling: Cool the milk down until it is “baby-bottle warm” (about 40-45°C). If it’s too hot, you’ll kill the good bacteria you’re about to add.
• Inoculation: Add a “starter culture” (this can be a few spoons of an old plain yoghurt). These are the “friendly” bacteria.
• Incubation: Keep the milk warm and still for 6 to 8 hours. The bacteria eat the sugar and turn the milk thick and tangy.
• Cooling & Flavoring: Once thick, put it in the fridge. You can then add sugar, vanilla, or fruit like strawberries.

Making Cheese (The Art of Curdling)

Cheese is essentially “concentrated milk.” We separate the solids (curds) from the liquid (whey).

How it’s done:

• Coagulation: We add something to the milk to make it “clump” together. In science, we use Rennet, but in many parts of Nigeria, farmers use the juice from Sodom Apple leaves (Wara) or even vinegar/lemon juice.
• Separation: The milk will divide into white chunks (Curds) and a yellowish liquid (Whey).
• Draining: We pour the mixture into a cloth or basket to let the liquid drain away.
• Pressing & Salting: The solid curds are pressed into shapes. Adding salt helps preserve it and adds flavor.

Note: “Wara” is a great example of local Nigerian cheese technology!

Making Butter (The Power of Shaking)

Butter is made from the fat in the milk. If you let fresh milk sit still, the cream (fat) rises to the top.

The Process (Churning):

• Cream Collection: Scoop off the thick cream from the top of the milk.
• Churning: Shake or stir the cream very vigorously. You are basically “beating” the fat globules until they stick together.
• The Break: Suddenly, the fat will clump into a yellow solid (Butter), leaving behind a watery liquid called Buttermilk.
• Washing: Wash the butter with cold, clean water to remove any leftover buttermilk (this prevents it from smelling bad later).
• Salting: Add a little salt and pack it tight.

Summary: What comes from where?

Safety and Quality Control

When processing milk, your kitchen or factory must be cleaner than an operating room.

• The “Sour” Rule: If the raw milk already smells sour, do not try to make yoghurt or cheese with it. The “bad” bacteria have already won.
• Sterilization: Always boil your containers and spoons before they touch the milk.
• Storage: Most processed dairy products still need to be kept cool to stay fresh.

Class Discussion / Practical Activity

1. Local Knowledge: Have you seen “Wara” being made in your community? What plant do they use to make the milk clump together?
2. Comparison: Why does yoghurt stay fresh in the fridge for 2 weeks, while fresh milk might only last 3 days?

The Butter Challenge: Give students a small, clean jar with some heavy cream. Have them take turns shaking it for 10-15 minutes until they see the butter form. (It’s a great workout!)