Guide to yogurt making: all the tips and tricks

I have been making homemade yogurt for five or six years. What began as a quirky hobby and means to save money has become so natural to me that I don't even think about the process, the advantages, or the unusualness of this activity anymore. It's really quite a simple and forgiving process, but there are many ways in which to damage (or think you've damaged) the finished product.

You see, because yogurt-making is a somewhat long but mostly hands-off process, the easiest thing that can go "wrong" is forgetting that you're making yogurt at all during one or another of the steps. Then comes the frantic Google search as you try to find out if you've ruined it all (spoiler: you probably haven't). In some cases I found ready answers, and in others I had to experiment and learn from the results.

So, with half a decade of experience in over-culturing, over-cooling, boiling, and forgetting my yogurt, I have decided to create the guide that I needed when I began my yogurt adventure (you know, be the change you want to see in the world and all that).

Guide to Yogurt Making: All the Tips and Tricks

The Supplies

You do not need a yogurt maker to make yogurt! Most likely you already have everything you need in your own home.

• A yogurt starter (more on this below)
• Milk
• A stove and pot to heat the milk
• A kitchen thermometer
• Glass jars with lids to hold the yogurt
• Some means to keep the yogurt at a consistent temperature for culturing. You can use a yogurt maker if you have one, but I've heard of using the pilot light in your oven, hot towels, a cooler filled with just-boiled water... You can get creative. My personal method is a heating pad on medium heat, inside a small cooler with a towel draped over the top. This works quite well for me, but I've also tried the boiling water and pilot light methods and had moderate (though less consistent) success with those as well. You may have to play around with it to find what works for you; make sure to test the temperature of your yogurt the first few times to get a feel for how it's working.

On Yogurt Starters

There are websites that sell so-called "heritage" yogurt cultures. They claim that commercial yogurt starters (i.e. the starter used for any yogurt that you'd buy in your grocery store) are not as viable as heritage cultures. The idea is that once you start a batch of yogurt, you can use a spoonful from that batch as the "starter" for the next batch, and thus have a self-perpetuating system so that you never have to buy yogurt again. According to these companies, commercial starters are not capable of indefinitely self-perpetuation and "wear out" after 3–4 batches.

In my early days of anxious yogurt production, I bought these heritage cultures multiple times and tried to build a lasting yogurt starter from them. Some people may be able to perpetuate their yogurt indefinitely from these heritage starters, but my experience was that after some number of batches (5, 8, 12, whatever), my yogurt stopped reliably producing more yogurt, and I'd have to buy more cultures and restart.

After spending more money than I should have trying to make the heritage cultures work, I tried the not-recommended method of using a spoonful of yogurt from the store (my rationale was, a quart of store yogurt costs about the same as a single heritage starter, but you can eat the rest of the container of yogurt, so if it doesn't work, at least you get something out of it). The result? I have still had to restart my yogurt cultures from time to time, but less frequently than with the heritage cultures! (In fact, sometimes I restart on purpose — when going out of town, for instance, it's easier to let the cultures die and just spend the few extra dollars buying a quart of yogurt when I get back, than trying to time my yogurt production exactly around travel).

Note that brand does make a difference; I have had more success with "nicer" brands like Nancy's than the cheapest store brand.

Lastly, make sure to make new yogurt every 5–7 days; yogurt is perfectly safe to eat after seven days, but after that the cultures may not be sufficiently active to produce more yogurt (though I've had success up to Day 9 or so).

The Process

Making yogurt is really quite a simple, forgiving process, but there are some key steps:

1. Heat milk on the lowest heat till it reaches 180ºF. (Estimate several hours for the heating/cooling process!)
2. Remove milk from stove and cool to 105–110ºF. 
3. Put your yogurt starter in your glass jar (~1 Tbl yogurt per quart of milk), pour in a little of the cooled milk, and whisk. Once smooth, pour the yogurt-milk mixture back into the pot and whisk gently.
4. Pour milk mixture into jar (s) and culture at a steady temperature of ~105ºF for 3–24 hours.
5. Remove yogurt from culturing environment and chill.

That's the simple part — but what happens if something goes wrong at one of these steps? Is your yogurt a lost cause? That's what the section below is all about (organized in chronological order for steps 1–5).

What can go wrong

What if I forget my milk on the stove and the temperature goes above 180º?

Your milk is still usable! Just remove from heat and proceed to step 2. (I actually think yogurt sometimes turns out a bit thicker this way, though I still try to avoid heating beyond 180º, because higher temperatures destroy more of the milk proteins.)

What if the milk is taking forever to heat and it reaches 167º and doesn't want to go higher?

Be patient! You can turn the heat up a little, but not much. There is something special about 180º; if you stop before you reach that temperature, your yogurt will not be as successful.

What if I forget my milk while it's cooling and it drops below 105º?

Your milk is still useable! Return to stove and heat on the lowest heat until it reaches 105-110º and then proceed to step 3.

What if took too long to heat/cool the milk and now I have to leave my house while it's still cooling down?

If the temperature has made it to 180º but you don't have time to wait for it to cool to 105º, put a lid on the pot so it will cool more slowly. If you're not away too long, it might not have dropped below 105º when you return, and you can just proceed to step 3. If it drops below 105º, just return to stove and reheat to 105º. I've even had good results putting the heated milk in the refrigerator overnight and reheating to 105-110º the next day and making yogurt at that point.

What if I forget I had yogurt culturing and it stays in its culturing environment for hours longer than planned?

Note there is a wide range for culturing times (3–24 hours), so if it goes a little longer than planned, don't sweat it. The longer yogurt cultures, the more sour it will taste (because the yogurt cultures are eating the sugars in the milk), but it's still edible and viable. The sweet spot for me is 5 hours, but I have no problem pulling it out after 4 or leaving it for 8 if that's what works best for my schedule. Make it work for you and don't stress it.

What if I test the temperature during/after culturing and it's fallen below 105 or gone above 110?

Figuring out how to culture yogurt in your environment may require some experimentation, but you'll likely figure it out after a few batches (for example, I found that I could make significant changes to the temperature by adjusting my heating pad between the low, medium, or hot settings, or adjusting how many towels I put on top). See below for the various effects on yogurt texture from culturing too cool or too hot.

What if my yogurt looks kind of thin and wobbly when I pull it out of the culturing environment?

Put it in the fridge before you despair — the chilling time really does help firm up the texture.

What if my yogurt turns out thin and runny?

There are various reasons why yogurt can have a thinner texture than expected. This is more common with raw milk, for example (see below). The temperatures really do matter — stopping the milk before it reaches 180º will result in thinner yogurt, and a culturing environment that falls below 100º will also result in thin, runny yogurt.

If you've followed all the steps correctly and it's still thinner than you'd like, you can strain it: line a strainer with a clean tea towel and place over a bowl. Pour the yogurt into the strainer and place in the fridge for 1–5 hours, until the desired amount of whey has dripped out of the yogurt (leaving you with thicker, "Greek" yogurt in the strainer). You can then toss the whey or use it in a variety of ways (protein in smoothies, hair wash, add to dried beans when soaking, etc.).

What if my yogurt's texture is grainy, lumpy, or otherwise inconsistent?

Heating your milk too fast in step 1 or culturing your yogurt too hot in step 4 is the most likely culprit for grainy texture or separation. 

Of course, some inconsistency in texture is normal (especially if you use milk that's not homogenized — expect to have a "cream" layer of yogurt at the top). After the yogurt has chilled and before eating, you'll want to stir it.

What if my yogurt totally fails to culture and all I have is warm, weird-smelling milk?

Let it go and try again. You'll get this.

Miscellaneous Tips

How long does homemade yogurt last?

Quite a while for eating purposes (I've kept it for a month, though that's probably not recommended). After about a week, yogurt cultures are no longer sufficiently viable to make more yogurt, though.

What kind of cultures do you need to make Greek yogurt?

This is a trick question! There are no cultures specific to Greek yogurt — Greek style just means that the yogurt has bee strained. See the question above about fixing thin yogurt to learn how to go about this.

How do you make your yogurt more or less sour?

The sourness of your yogurt is mainly dependent on how long it's cultured. The longer you culture = the more sour the yogurt. Fiddle around with it to figure out how you like it.

Can you make yogurt from raw milk?

Yes, this is what I always do! However, heating it to 180º means that it's technically not raw anymore; you've essentially home-pasteurized the milk. Early on in my yogurt days I attempted recipes that only heat the milk to very low temperatures, thus keeping it raw. The issue is that the healthy bacteria present in raw milk are then competing with the yogurt bacteria. The result is that the yogurt never gets very thick (it's more like kefir at this point). Since I eat yogurt for the benefit of the fermented cultures anyway (not the raw milk bacteria), I've made peace with the slow, low pasteurization process that allows those bacteria to take over the milk and produce a thicker yogurt (though commercially-pasteurized milk probably still makes an even thicker yogurt). And, by heating the milk very slowly and capping it at 180º, you can still maintain the integrity of the milk proteins, which are destroyed by ultra-high temperature (UHT) pasteurization, the method used to treat most commercially-sold milks.

That's it for this guide to yogurt making! I hope my experiences are helpful to someone else trying to get started in this world. 

Happy spring,