Introduction: Greek Yogurt, From Scratch!
It's amazing the things you don't pay attention to or simply forget from when you were a kid. A couple of years ago I discovered how fantastic homemade yogurt can be: easy to make and really great tasting. It turns out that my Armenian grandmother used to make it all the time, on her wood stove! I never paid attention to it, and always wondered -- but never asked -- what the jar of white stuff was, sitting on the floor behind the stove in her kitchen. It turns out to be one of the most healthful, flavorful and economical foods you can make on your own. Far cheaper than the store-bought versions, and pretty simple once you get the hang of it.
I have essentially taken the process my grandmother -- and countless others before her -- used and "modernized" it a bit. It's still cooking, cooling and incubating fresh milk with a little starter, but I have developed a method of culturing the milk that doesn't require the wood stove to be burning 12 months a year. I have gotten into a good rhythm, producing 2 or 3 batches a month for a couple of years now. The starter for the next batch is a few ounces from the current batch.
This process may be a bit more "technical" than others, and I include some alternatives I've seen that are also successful. What I think I've done is to create a pretty consistent and reproducible result every time. If you're willing to invest a little bit of money and a few gadgets into the process, you will be rewarded with a really tasty result that's 1/3 the cost of what you could find in stores. Or, if you want to give the process a little more attention during each batch, then skip the more technical elements and stick to the basics. Either way, you end up with fantastic, fresh yogurt!
Step 1: Components
Aside from fresh milk, there are a few components I use to make yogurt. This method starts with a gallon of milk, so the containers all support that capacity. These are the kitchen components I use for the different steps, essentially in the order I use them. You likely have most of these in your kitchen already.
- 6-quart stock pot or "dutch oven"
- Candy thermometer or digital thermometer that has accuracy between 40 deg and 200 deg F
- Spoon, ladle or silicone spatula
- Soup bowl
- Stainless steel whisk
- Yogurt culture
- Large salad bowl 1/2 filled with ice water
- 1-gallon glass jar with a lid
- 9" x 19.5" electric seedling heat mat
- Temperature controller
- Towels, for insulation
- 4-quart mixing bowl
- Smaller bowl that nests inside the mixing bowl
- Tea towel or other cloth, for straining the yogurt
Step 2: A Brief Note About Cleanliness and Bacteria
I make a solid effort to keep all utensils and containers clean and dry, but I don't sterilize everything. I start with utensils and containers clean and dry from the dishwasher. If you're unsure that all the soap residue has been completely rinsed from these, then rinse them thoroughly and make sure they're dry before using. The pot I wash thoroughly and rinse with filtered water before letting it air dry. The jar gets washed, rinsed and air dried right after the straining step, so it's ready for the next batch. Beyond that, I don't feel the need to have a "sterile field" to make yogurt.
Your own cooking environment can have an impact on the types of bacteria present in your yogurt. There are naturally occurring bacteria all around us, and some may well be the "thermophilic" (active above room temp) type that cultures yogurt. The yogurt you make will be your own special blend of the starter you choose and whatever happens to make its way into your next batch. That's what makes it your own. Enjoy it!
Step 3: Heat the Milk
I start with a gallon of the freshest milk I can find. I typically use 2% milk with no antibiotic or GMO additives. Use whatever you can find, just make sure it's nice & fresh.
I have also used full-fat unpasteurized milk from a dairy farm, and the results are spectacular. The yogurt has a golden hue to it from the milk fat, and the mouth feel unctuous, almost like thick whipped cream. I don't have easy access to raw milk where I live, but when I can find some, it's a real treat!
Update(16 Sept, 2015): I made a batch of raw goat's milk this summer. It was very successful in terms of consistency, with the familiar goat cheese taste. Goat cheese fans will love it. It's great in savory recipes, but it's not my favorite breakfast yogurt...
- Reserve about a 1/4 cup of milk, so the milk with the starter will fit in the 1 gallon jar.
- This does not get used in the process, so just use it anywhere you use fresh milk. In coffee, perhaps?
- Pour the rest of the milk into the stock pot and position the thermometer above the bottom of the pan.
- I use a digital cooking thermometer, but I have also used a candy thermometer with good success.
- Heat the milk on medium-high heat and gently stir constantly.This takes me about 25 minutes for a gallon.
- Heat set too high or not enough stirring can cause milk protein "grains" to form.
- At 190 deg. F take the pot off the heat.
Heating the milk affects the milk proteins and helps thicken the yogurt. It also has a pasteurizing effect and eliminates other bacteria so the starter can do its job all on its own.
Update(16 Sept, 2015): A friend suggested to keep the milk at the 190 deg. F temp for 5-6 minutes before cooling. This helps further thicken the final yogurt. I have found that it results in more yogurt solids, so it ends up with a little more than 2 quarts of yogurt and a little less than 2 quarts of whey. Yay, more yogurt!
Step 4: Cool the Cooked Milk & Add the Starter
The heated milk needs to cool, either on its own or in an ice bath. I use an ice bath with the thermometer in place to speed the process and keep a skin from forming.
The amount of starter needed is relatively small, and too much can actually cause problems during incubation. The ratio I use is about 1.5 tablespoons per quart, so for a gallon of milk I use about 1/3 cup of yogurt from my last batch.
Your initial starter can be any live culture yogurt you can buy in the grocery store, or there are sources for yogurt cultures online, as well. Once you have a successful batch made, some of that can be used as the starter for your next batch! I have been using previous batches for about the last 30 batches, almost a year.
Update(16 Sept, 2015): I'm now up to almost 2 years of propagating fresh batches with previous batches!
- Cool the milk in an ice bath to 125 deg F stirring regularly to speed the process.
- I use a large mixing bowl 1/2 filled with ice water that the stock pot fits into.
- Ice water in a stopped-up sink works well, too.
Step 5: Incubation
This is where the more "technical" part of my process begins. The bacteria need a slightly elevated temperature to do their work. This range is somewhere between 108-115 deg F depending on the cultures used. I have developed a process for incubating the milk at a consistent 108 deg F. I can set it up and walk away until the incubation process is finished. I leave it for 12-14 hours before I remove the incubation heat.
The essential function of the incubation process is:
- Keep the milk and starter mixture warm and undisturbed for several hours.
There are many ways of accomplishing this. Place the jar in an oven with a pilot light, or behind a hot wood stove. I have a friend who uses hot water in a covered camping cooler and mostly submerges the jar for several hours. You can use a heating pad with a towel over it, put the jar on that and cover it all with a large pot. Another technique uses a crock pot. I have a combination of an electric seedling heating mat and a digital temperature controller. This keeps the jar at a steady 108 deg. F until I turn it off.
- Pour the milk & starter mixture into the glass jar and cover.
- Attach the temperature probe to the outside of the jar.
- Make sure the probe has direct contact with the glass jar.
- I use a small piece of foam between the probe and the heat mat so the temp reading comes from the jar and not the heating mat.
- My controller has Celsius only, so I use 42 deg C.
108 deg F is at the low end of the incubation temperature range. I have tried a higher temp for less time, and that works, as well. I use the low end so the time frame is more forgiving. I have left a batch to incubate for 16 hours (I forgot about it!) and I have taken it out in as little as 10 hours and the results are not too noticeably different. Essentially, the longer a batch incubates, the more sugars the bacteria consume, which affects how tart a batch will taste. Experiment and find a combination that works for you.
A little History of My Temperature Controller
I first started with making yogurt by putting the jar to incubate on the hot water heater, which is next to the furnace in the basement of our house. This worked great all winter, but come spring when the furnace stopped firing on a regular basis, the results were disappointing. The batch would not set up and the bacteria just didn't have enough heat to do their job. I switched to the seedling heating mat plugged directly into the wall, and kept checking the temperature of the batch with a quick-read digital thermometer, opening or closing the towel wrap to regulate the temperature. This was time-consuming and unpredictable.
I discovered a temperature controller available online that could serve to regulate the heating mat power. This device monitors temperature for a set range and activates one 120-volt relay for heating and another for cooling. It required some hands-on skills -- working with AC voltage and electrical wiring -- to build the assembly around it to use it for controlling the heating mat.
Once I built the temperature controller, it was a matter of attaching the temperature probe to the jar, wrapping the heating mat around the jar, and bundling it up in towels for insulation. Now I can plug it in and forget about it until the incubation process has completed. I usually aim for just after dinnertime to put up a new batch, so it's ready to chill first thing in the morning.
I am considering an instructable for assembling the temperature controller. If you're interested in having one built for you, please let me know.
Step 6: Cooling & Straining the Fresh Yogurt
At this point, the yogurt is ready to eat. You can transfer it to a mixing bowl and whisk it up to make it smooth, and chill it to stop the fermentation process. I prefer to strain it to remove much of the whey. This is the classic "Greek" style of yogurt, thick and without the liquid whey that unstrained yogurt has.
This cooling step is one I have not seen in other recipes. I have found that cooling the cultured yogurt in the jar before straining it results in a firmer texture. It seems to let the yogurt solids collect more easily. I have tried straining the warm cultured yogurt, but I've found that a noticeable amount of yogurt solids end up in the whey. Chilling it in the big jar for 12-18 hours results in clear whey with almost no yogurt solids in it.
- Cool the jar of cultured yogurt for 12-18 hours before straining
- In the winter I put the jar outside until it's cool, then transfer to the refrigerator.
- In summer I put the warm jar in the refrigerator and surround it with ice packs from the freezer to keep the refrigerator from getting too warm.
- Update (16 Sept, 2015): I've been tinkering with this step, and I've determined it's really important for the yield of yogurt to whey. a short amount of time cooling seems to cause more of the solids to end up in the whey. So, don't skip this step if you're going to strain it for Greek style yogurt.
The result should be 1 part thick Greek yogurt and 1 part whey from 2 parts milk.
From a gallon of milk I get 2 full quarts of thick yogurt and 2 quarts of whey. Both go into containers and into the refrigerator. When I finish the first quart it's time to start the next batch!
Chill the yogurt and enjoy the fruits of your labor! It should easily keep for 2 weeks or more stored covered in the refrigerator.
Step 7: All the Whey...
This process generates a lot of whey that is super nutritional and has a lot of uses in the kitchen and in the garden, too. I use it for soaking beans and to replace water in some baking recipes. When I get too much to keep in the refrigerator, I pour the excess into the composter.
There are lots of ideas online for using whey left over from making Greek yogurt, including food preparation, cosmetics, animal feed and gardening. Here are some ideas from different websites for what to do with the whey you generate from straining your yogurt: