How is Yogurt Made?

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Yogurt is made when specific bacteria are added to milk in a controlled environment and allowed to ferment. The majority of yogurt made in the United States is produced with cow's milk, but the milk of other species, including sheep, goat, and camel, is also used to make yogurt in other parts of the world. Yogurt is much thicker than plain milk and often has chunks of material in it. It also has a distinctive tangy flavor, caused by the bacterial fermentation.

For a dairy product to be called yogurt, it must contain two bacteria: Streptococcus thermophilus and Lactobacillus bulgaricus. Many types of yogurt incorporate other species as well, including Lactobacillus acidophilus and Lactobacillus casei. In many countries, yogurt must also contain live bacteria and remain unpasteurized, with pasteurized yogurts being specially labeled. Pasteurized yogurt has a long shelf life and does not need to be kept refrigerated, but it also doesn't have the health benefits of live yogurt.


When yogurt is made, milk is heated to approximately 200° Fahrenheit (93° Celsius) and kept at that temperature for 10-30 minutes, depending upon the thickness desired. For thicker yogurt, the milk is heated longer. Next, the milk is rapidly cooled to approximately 112° Fahrenheit (44° Celsius) and mixed with a yogurt starter, which contains the necessary bacteria. This dairy mixture is placed in clean containers and incubated for a minimum of four hours at 100° Fahrenheit (37° Celsius). The longer the incubation, the more tart the yogurt, because more acids will develop.

To stop the incubation, the yogurt is placed in a cool environment such as a fridge. Kept cold, it will keep for approximately ten days. Yogurt can be made at home using commercial yogurt as a starter.

The most important step in the yogurt making process, and what creates the characteristics consumers think of when they imagine yogurt, is the introduction of the bacteria. The bacteria consume natural milk sugars and excrete lactic acid, which causes the milk proteins to begin to curdle and create a more solid mass. At the same time, the increased acidity of the dairy is too high for most harmful bacteria, so the yogurt keeps itself clean. Other bacteria can be added for flavor or health benefits, especially Lactobacillus acidophilus.

Yogurt is rich in protein and minerals and can in theory be drunk by people suffering from lactose intolerance, because it contains an enzyme that breaks down lactose in the intestines. Yogurt containing Lactobacillus acidophilus is often ingested by women attempting to avoid yeast infections, because it creates an environment too acidic for Candida albicans to thrive in.


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Post 82

This is a very informative page. Thank you!

Post 80

So making your own yogurt won't get you in trouble with anyone, right?

Post 76

@anamur: I think commercially, this is how companies make their yogurt, in a controlled environment, measuring the temperature and using special yogurt cultures. But all of this is not necessary when you're making yogurt for yourself at home.

My mom has been making yogurt for the family for years. What she does is she just boils the milk and then lets it cool down until it is warm. It should not be hot enough to burn your finger but it should not be cool either. Then she puts a couple of spoonfuls of yogurt into the milk. Puts the lids on, covers in a blanket and keeps it anywhere between four and eight hours, depending on the time of the

year and temperature at home.

You can open it up in between and check to see if it has gotten firm, which means the milk is cultured. Then you put it in the fridge and eat the next day! It's so easy! No science required at all!

Post 75

I was hoping to make yogurt at home because I eat a lot of it and it's not very cheap. But this sounds so complex! How can I possibly control the temperature and where do I get yogurt starter?

Post 74

@anon247128: That's actually normal. The yogurt bought from stores last longer because they put artificial preservatives in them that are actually bad for you. Natural yogurt should not last more than two weeks. Just make it in small batches that you can finish up in a week.

It might seem like more work but it's worth it. Natural yogurt tastes better and is a lot healthier than store-bought ones.

Post 61

I made yogurt myself, but it won't keep more than two weeks. Why?

Post 59

Nice to know how to make it because i can go home and make it for my family.

Post 55

thanks a lot. i really don't care if the article is wrong because it saved me from getting into crap with my old boring biology teacher.

Post 54

This is a poorly written article. The milk is usually heated to 80 degrees Celsius, then cooled to about 37 Celsius. This article fails to mention that a starter culture is added to grow the bacteria. Then it's incubated at about 42 Celsius.

To the person who said "All the recipes require boiling the cow or ewe milk at temperatures that destroy all the probiotics and enzymes to keep the yogurt healthful." The milk is not being boiled. It is heated to kill harmful bacteria, and in that process some beneficial bacteria does get killed. But because you add the yogurt starter before incubation, you are growing beneficial bacteria back into the milk. So the probiotics are restored and you don't have to worry about harmful bacteria.

Post 52

That was cool! Helped me on my assignment! Thank you wisegeek. I'll use your help again!

Post 51

Don't believe any of the hype about the health benefits of Greek Yogurt or any other kind of yogurt.

All the recipes require boiling the cow or ewe milk at temperatures that destroy all the probiotics and enzymes to keep the yogurt healthful.

Don't be conned! If you still want to eat it, that's fine, but don't think it provides the health benefits you were probably expecting.

Post 48

This site helped me and my kid learn what is in yogurt and now that I know I think I will stick with Blue Bunny ice cream. Each to their own.

Post 38

But what are the health and safety issues when making yogurt?

Post 26

well my friend and i argued over what yogurt was made of and you proved me right thank you. oh yum curdled milk

Post 12

gee golly wizards! I am a yogurt jedi-master now!

Post 11

no wonder i hate yogurt my mother makes me eat it every day. don't get me wrong im crazy about science and this really helped me realize what about yogurt i never liked...i never knew before that it was a bacteria with a tangy flavor *eww*

Post 6

Recently I have started to make my own yogurt. I make it from non fat milk, and use store bought yogurt with live cultures as a starter.

The stores offer a variety of yogurt, so it is good to check out different ones to see which one suit your taste the best. Yogurt making is an easy process, it is healthy, and it tastes very good.

I am noticing though, that the texture is not the same as store bought. Home made is a tad more grainy, where the store bought is more smooth.

The taste though, is not affected at all.

There are yogurt makers on the market, mine is 1 qt size, that are very reasonably priced, and make the yogurt making process a breeze.

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