Yogurt has been eaten for centuries. Long before there was factory made yogurt people have been making this probiotic rich milk ferment.
The version of yogurt which you can buy at the store isn’t really yogurt at all but rather a thin version of what yogurt really is. It used to be a culture made up of a wide variety of bacteria which was strong enough to perpetuate itself as long as it had fresh milk to ferment.
The yogurt you can buy at the store today is made from a collection of bacterial cultures which have been identified as the main ones which are in the original yogurt.
There are three ways to make homemade yogurt.
Use a packaged yogurt starter
This method produces a version of yogurt like the store bought type. The powder is made up of the main cultures which produce the store bought version and is easy to store.
To make yogurt using a package simply warm your milk up until it almost boils and then cool it to body temperature. Once it is cool mix in the powdered yogurt starter and place in a warm location like the oven with the oven light on. Leave undisturbed for 12-24 hour depending on the amount of lactose you want the yogurt to contain.
The longer you leave it the more lactose is consumed by the cultures in the yogurt starter.
There are yogurt makers which keep the yogurt at the ideal temperature. They are great if you find that you like your yogurt fermented longer and use the oven daily.
Use store bought yogurt as the starter
Store bought yogurt has living cultures in it which fermented the milk into yogurt. They are fresh and still viable.
The method is the same as above except you mix in about ¼ to 1 store bought yogurt rather than the powdered starter.
Since the yogurt you get at the store only has a few of the bacterial cultures which made up the original yogurt this method will work with fresh store bought yogurt but if you try to culture more yogurt from the fresh batch you will find it slowly changing flavor and consistency until it no longer makes yogurt but rather simply goes off.
This is because the starting culture does not have the diversity of heritage yogurt which is able to maintain itself over a long period of time.
Use a heritage starter
Heritage yogurt can be used indefinitely just as long as it is fed a fresh supply of milk on a regular basis. There are types which need a warm environment to multiply like the store bought powders or types which do not need heat.
When you purchase a heritage yogurt starter it will come in a powder like the store bought yogurt starters.
Follow the instructions on the package. Some types do not require external head above room temperature whereas some do.
Once you have made one batch of yogurt with your starter then you can use a little bit of your current batch for the next batch. This is called backslopping in fermentation lingo as sounds much like what it is.
As long as you continue to make fresh batches of yogurt from previous batches you will not have to purchase another starter.
