How to make yogurt – Prokaryote project – Biology

Home » How to make yogurt – Prokaryote project – Biology
Print Friendly, PDF & Email
a brown-skinned girl pouring yogurt from a cup into a big pot of milk - how to make yogurt

A girl making yogurt in Mongolia: how to make yogurt!

Yogurt and bacteria

To see some prokaryotes in action, you can make your own yogurt. Yogurt is what happens to milk when bacteria get into it and reproduce. The bacteria eat the sugar(lactose) in the milk for energy to live and reproduce themselves. They break apart the sugar molecules to get energy. They have lactic acid molecules left over, which they push out of the cell to get rid of them. These lactic acid molecules react chemically with the protein molecules in milk and make the proteins unfold and stick to each other. That makes your liquid milk turn all gloppy – that’s yogurt.


A video showing how to make your own yogurt

How to make yogurt

Get some yogurt with live cultures in it at the store (you might have to look in the healthy food section; if it has live cultures in it, it will say so on the carton), and get a thermometer – any glass thermometer will do. Those live cultures are your bacteria. Use fresh yogurt you just bought that day. In the microwave, heat up a bowl of milk for about two minutes until it is warm. It should be just 110 degrees Fahrenheit – not more. That is a good comfy temperature for the bacteria to reproduce in. If it is too hot, wait for it to cool down a little, or add a little cold milk to cool it down.

When the milk is the right temperature, put a couple of spoonfuls of yogurt in another bowl. Add a quarter cup of the warm milk to it, and mix it up. Then add the yogurt-milk to your larger bowl of milk and mix it up. Cover the bowl with a dishtowel to keep out bugs and leave it on a sunny kitchen counter or back porch where it will stay warm, or put the warm bowl inside your microwave, which is insulated and will keep it pretty warm. You want it to be about 80-90 degrees Fahrenheit, so this is easier to do on a hot day.

Curds and whey

After about eight to twelve hours, your milk should all have turned into yogurt (if it hasn’t, give it a little longer). You can eat it plain, or add berries or jelly if you like it better that way. Or, to make thicker yogurt, pour the yogurt into a colander lined with paper towels in it, put the strainer over a bowl, and wait another four hours or so. The thin liquid in the bowl is whey, and the stuff in the strainer is curds (like in the nursery rhyme about curds and whey).

Did this help you learn how to make yogurt? Let us know in the comments!

What are prokaryotes?
What are eukaryotes?
Where did people first start eating yogurt?

Bibliography and further reading:

What are prokaryotes?
Biology
Chemistry
Quatr.us Home

By |2018-04-16T10:27:53+00:00May 28th, 2017|Biology|2 Comments
Cite this page: Carr, K.E. How to make yogurt – Prokaryote project – Biology. Quatr.us Study Guides, May 28, 2017. Web. September 25, 2018.

About the Author:

Dr. Karen Carr is Associate Professor Emerita, Department of History, Portland State University. She holds a doctorate in Classical Art and Archaeology from the University of Michigan. Follow her on Instagram, Pinterest, or Facebook, or buy her book, Vandals to Visigoths.

2 Comments

  1. Edyn Walker November 30, 2017 at 8:23 pm - Reply

    Is there anything about were do they get milk in the Indus Valley?

    • Karen Carr December 1, 2017 at 10:16 am

      In the Indus valley, people actually got their milk mostly from water buffalos, rather than from cows. That’s still true today. But they did use plenty of dairy products. Because it was so hot, milk went bad quickly, so they mostly made it into yogurt or cheese.

Leave A Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.