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I'm sure you know that yogurt comes from milk, but did you know that bacteria are also a key ingredient?
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Yes, bacteria! But don't worry, these are good bacteria and are often called probiotics.
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Your gut has thousands of types of bacteria happy living inside whose job it is to aid digestion.
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Yogurt is thought to be a good vehicle to bring more of these good bacteria in.
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So in this video we're going to learn a bit more about how yogurt is made.
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First we need milk.
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Before we start the next steps, all of our equipment needs to be sterilised to kill any unwanted bacteria and other microorganisms.
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Now we are ready to start.
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The milk is heated to somewhere between 85 and 95 degrees Celsius for between 15 and 30 minutes.
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This is a process called pasteurisation and is also done to kill any bacteria and other microorganisms that are naturally found in the milk.
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The milk is then homogenised.
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This breaks down the fat droplets in milk to make them smaller, so that they stay suspended in the yogurt rather than sinking and making it all lumpy.
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So we've sterilised our equipment, then pasteurised and homogenised the milk.
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Now the mixture is cooled to 40 to 45 degrees Celsius and we add our special yogurt making bacteria.
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The mixture needs to be cooled first so that the bacteria aren't killed by the high temperature.
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You might be wondering why on earth are we adding bacteria when we've gone to all the effort so far of killing all the bacteria.
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We're adding lactic acid bacteria, which are also used in cheese manufacturing.
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The two species used to make yogurt are lactobacilli and streptococci.
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But don't worry, you don't need to learn these names, just remember that lactic acid bacteria are added.
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These lactic acid bacteria are known as the starter culture.
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The bacteria ferment the milk and change it into yogurt.
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Lactose is the main sugar in milk and during fermentation the bacteria turn the lactose into lactic acid.
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The bacteria also start to digest the milk proteins.
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Fermentation takes many hours, and during this time the mixture is kept at the optimum temperature of 40 to 45 degrees Celsius, so that the bacteria can work its fastest.
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As fermentation produces lactic acid, a type of acid, the pH of the milk drops to about pH 4.4.
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This is why natural yogurt has a sharp tangy taste.
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As the pH levels drop, the milk solidifies to become raw yogurt.
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Once the pH drops to a low, the lactic acid bacteria that make the yogurt also stop working, so the yogurt doesn't become too solid.
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The pH drop also stops any bad bacteria growing.
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The solidification happens because the proteins begin to coagulate.
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Coagulation is when something which is liquid turns into a more solid state.
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So you've sterilised the equipment, then pasteurised and homogenised the milk.
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Added lactic acid bacteria, so fermentation happens and then coagulation.
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The mixture is now stirred and cooled to five degrees Celsius and we've made the natural and flavored yogurt.
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At this stage we can add flavorings and fruit.
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Now it's ready to be packaged and sold - delicious!
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Can you match the words to the definitions of the different stages of the yogurt making process?
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Pause the video and give it a go!
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Did you get them right?
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Now what about completing the missing words?
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Again pause the video and work them out.
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Did you get them right?
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So there we have the process of yogurt making - from milk to a tasty strawberry flavored yogurt.
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If you liked the video, give it a thumbs up and don't forget to subscribe.
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Comment below if you have any questions.
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Why not check out our fuseschool app as well? Until next time!