Since I shared my Instant Pot yogurt making recipe in 2022, I’ve gotten a ton of questions about the yogurt making process (also I can’t believe I am still doing this every couple weeks years later).
Below, find a selection of the most common questions I’ve gotten about homemade yogurt (plus a few others!) covering the basic process of making yogurt and the microbiology behind it. If I didn’t answer your question, please leave it in the comments below!
Does it matter what type of milk I use?
You can generally follow the same recipe for skim milk, 1% milk, 2% milk, or whole milk. Whole milk will produce the creamiest yogurt of these options. My personal preference is using 1% milk but I have had luck with all of these types.
Can I use raw milk to make yogurt?
Yes. But a warning: You will see a lot of recommendations to heat the milk to a lower temperature if you are using raw milk (110°F instead of 180°F). I personally cannot recommend this. Since raw milk is not pasteurized and you have no idea what bacteria is actually in there, you may end up culturing bacteria other than yogurt bacteria. Microbes found in raw milk can include pathogens like Listeria, Salmonella, Campylobacter jejuni, and Escherichia coli. I would feel uncomfortable using milk that hasn’t been pasteurized.
What about using non-dairy milk? Can I use almond milk, soy milk, or coconut milk to make yogurt?
Yes! However, you might want to add a thickener to your yogurt such as pectin, agar-agar, cornstarch, etc. So far, the only non cow milk yogurt I’ve made was soy milk yogurt using cornstarch as a thickener.
How do I know when my yogurt is done?
The time it takes for your yogurt to finish depends on several factors including the temperature of incubation and the amount of starter culture you put in. Putting in more starter culture could make the fermentation process go faster and incubating at temperatures that are too low can make it go longer. The yogurt will be done when it jiggles a little bit (think: jello). It’s okay if some of the whey has separated out.
My yogurt is runny. What happened?
It’s possible you don’t have enough fermentation happening (ex: if your temperature is too low or you used too little starter). In these cases, give it more time. It’s also possible that your starter culture is dead and so no fermentation has occurred — in this case, I’d toss the batch.
How long will my homemade yogurt last?
My yogurt stays fine for 14 days. Many people will save a bit of their previous batch of yogurt to make the next batch but I don’t do this because I feel like it could be a bit long after sitting in the fridge for two weeks and the yogurt microbes might not be as happy. I prefer to freeze yogurt from the store in an ice cube tray and use that to start the next batch.
What are the most common bacteria that make yogurt?
Streptococcus thermophilus and Lactobacillus delbrueckii subspecies bulgaricus (aka L. bulgaricus) are the primary bacteria used together to make yogurt. Some yogurts will have other lactobacilli and bifidobacteria in them as well (see below).
Can I use probiotic capsules to make yogurt?
I’ve received a lot of questions about using probiotic supplements (like the ones from the pharmacy) to make yogurt. I haven’t done that myself but have found success stories on the internet with specific species of bacteria – you’ll have to check Reddit, other blogs, etc. for these. This person on Reddit actually documented several probiotic capsules and how well they worked or didn’t work for making yogurt. It seemed like half of this person’s experiments worked and they ended up concluding that the probiotics that worked for yogurt were the ones that contained S. thermophilus plus some other bacteria for best results.
From a microbiological point of view, this makes sense because many of these probiotic capsules do not contain the core yogurt bacteria mentioned above. Lactobacillus rhamnosus and Bifidobacterium longum are two species of bacteria common in probiotic supplements, but they are only used sometimes as optional strains in yogurt (i.e. they aren’t S. thermophilus or L. bulgaricus that are the “core” bacteria for making yogurt).
So if you’re trying to use probiotic supplements to make yogurt, you may want to look at starter capsules or powders specifically for yogurt. There are several freeze dried starters available for that (ex: from Cultures for Health).
Does the “live culture” I see on yogurt containers means there are probiotics?
Not necessarily. Probiotics by definition are live microorganisms that give a health benefit (ex: better digestion). While probiotics are a type of live culture, not all live cultures are probiotic.
Are there certain strains of bacteria I could use to give my yogurt specific health benefits?
I would say that the health benefits of adding certain strains is limited. Aside from the “core” yogurt microbes mentioned above, there’s evidence on how certain strains of bacteria can help in specific health contexts. For example, some Lactobacillus rhamnosus has been shown to reduce acute diarrhea and alleviate irritable bowel syndrome symptoms. That said, yogurt typically contains fewer bacteria than a probiotic supplement and not every strain survives stomach acid well. Because probiotic supplements have more bacteria and some of these supplements are also delayed-release (ex: coated to withstand stomach acid), you could see a better effect from supplements than yogurt.
Alrighty, that’s it for now! I hope this was helpful and if you still have some burning questions about making yogurt, please leave them in the comments.
You can also find my yogurt making recipe here and if you’re interested in trying another fermented milk experiment, see this blog post about making kefir.
Featured image source: Mustafa Türkeri