Making sure your home is always clean, sanitized and free of germs is always at the top of our priorities. But there are some bacteria, like the ones that turn milk into yogurt, that are actually good for you.
Yogurt is now ubiquitous and can be found in any supermarket or corner store but its origins go back a long way. Nomadic tribes in places like Central Asia, Eastern Europe, and the Middle East would carry milk in pouches made of animal skin. The beneficial bacteria that kick-started the process of fermentation thrived in these places because of the temperatures.
Slowly but surely, yogurt made its way all across the world and is now consumed in large quantities because of its health benefits and characteristic taste. In order to make yogurt at home, you need a starter culture. So what is yogurt starter culture and where can you get it?
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What Is Yogurt Starter Culture?
A yogurt starter culture contains bacteria that ferment the milk by feeding on the lactose and converting it into lactic acid. This lowers the pH balance of milk, i.e makes it more acidic and gives it the tart taste that’s mostly associated with yogurt.
Different starter cultures will produce yogurt that has a taste, texture consistency specific to that culture. Yogurt starter cultures are broadly divided into types — commercial, direct-set starter cultures and heirloom, re-usable cultures.
The first step towards discovering what is yogurt starter culture was in 1904. The Bulgarian scientist Dr. Stamen Grigorov analyzed the contents of yogurt and identified the main bacterium that caused the milk to ferment. It came to be known as Lactobacillus bulgaricus. Later, scientists also identified other bacteria including Streptococcus thermophilus.
Commercial yogurt manufacturers and microbiologists began isolating and blending strains of these bacteria to create customized starter cultures. After testing, they were able to predict what kind of yogurt would be produced by a particular starter culture and the process of making yogurt became more standardized. This suited industrial production because the results were guaranteed.
When you add a small amount of store-bought yogurt to milk and let it ferment, you are using a commercial starter culture. It is believed that these starter cultures, also known as direct-set or single-use cultures, can only be used once to produce a new batch of yogurt. If you use this new batch of yogurt to inoculate more milk, the results will become unpredictable and the taste will fade over time.
Heirloom starter cultures, also known as re-usable or mother cultures, are bacterial cultures that have evolved over time. Nature takes over and scientists do not pick and choose which strains of bacteria will work best. Families in many parts of the world have traditions of making homemade yogurt and will save small amounts from a previous batch to make a new batch.
These starter cultures last for generations. A Jewish bakery in New York has preserved the tradition for more than a hundred years. Indians who immigrated to the United States in the ‘80s and ‘90s hid yogurt in their clothing so that they could take it through security checkpoints.
Heirloom starter cultures are known to preserve their taste and quality over multiple batches. These cultures should be reused every week so that the bacteria remain strong. You can purchase heirloom cultures online or request a friend who makes yogurt at home to give you a few spoonfuls.
How to Activate Yogurt Starter Culture
What do you do once you’ve purchased heirloom starter culture or have some leftover yogurt? Here are some tips to get you started.
If you do not have an heirloom starter culture, use some store-bought yogurt to begin the process. Try and find yogurts that are organic, without too much-added sugar and preservatives.
Heat the milk at 180 degrees until it comes to a boil. This thickens the milk. Then let it cool down to 115 degrees where it’s not too hot but it’s not completely cold either.
It’s now time to add the starter culture. Add 2 tablespoons for 4 cups of milk. Transfer the milk to a jar and keep it in a warm place for 6-12 hours. If you’re unable to find a warm place, wrap the jar in kitchen towels.
Once the yogurt has set, you can place it in the refrigerator to thicken it further and increase the acidity. If you want an even thicker version, you can strain it or use a cheesecloth and let it drain. The whey that is left behind can even be consumed as a drink by adding a little salt or sugar.
Using an Insulated Cooler
If you’re making yogurt using an insulated cooler, as popularized by Sandor Katz, you’ll need to start off by heating water to approximately 115 degrees. Then pour this water into the insulator.
Follow all the steps in the basic method regarding the milk and the starter culture. Heating the milk is essential because it breaks down the proteins and allows the milk to be reconstituted by the fermentation. Heat the milk slowly and stir constantly if you want your yogurt to have a better texture.
Place the container with the milk and the starter culture inside the cooler and let it sit for 4-8 hours. You can keep a thermometer inside the container and check it periodically in case you need to add more warm water to the cooler. The longer you let the milk ferment, the stronger the flavor will become.
Using an Electric Yogurt Maker
Yogurt makers give you more ease and flexibility. You have to follow the steps in the basic method until you put the mixture of milk and yogurt starter culture into a container. Many yogurt makers include jars while some have an in-built container.
They also come with timers, so you won’t have to worry about whether you’ve left milk out for too long. Yogurt makers also keep the temperature constant and ensure that the fermentation process is smooth.
Nothing beats the flavor of food that you have made with your own hands. Yogurt is a rich source of proteins and vitamins and homemade yogurt has improved health benefits because it doesn’t contain any of the preservatives that are added to commercial yogurts.
Making yogurt at home can also be a communal activity, so if your friends and family are interested, you can talk about what exactly a yogurt starter culture is and begin your fermentation journey together.