Why Your Yogurt Isn’t Turning Out: Easy Fixes

Homemade Yogurt

Is your raw milk yogurt runny?  Does your homemade yogurt separate?  Is it foamy?  Too sour? Too liquid?  Not sour enough?  Each week through Nourished Kitchen’s facebook page, and by email, I receive several questions about troubleshooting homemade yogurt.  Here’s a list of the most common questions on making homemade yogurt, working with starter cultures and troubleshooting your yogurt when things go a little awry.

How do I make yogurt?

To make yogurt, you need milk and a starter culture.  The starter culture is typically freeze-dried yogurt that contains live active bacteria, and each yogurt may offer a different flavor or array of beneficial bacteria.   There is a wide variety of yogurts from which to choose, each with their own unique characteristics though they share the common benefit of producing a cultured dairy product that is rich in food enzymes, increased B vitamins and beneficial bacteria.  After culturing with a powdered starter, you can use the yogurt you have prepared as a starter for future batches of homemade yogurt (this does not apply to raw milk yogurt, see below).  You also need milk which can be any mammalian milk, cow’s and goat’s milk being the most commonly used varieties.  For questions on non-dairy yogurt, continue ready below.

What are “thermophilic” and “mesophilic” yogurts?

Thermophilic means “heat loving” and it refers to yogurts that culture best at a slightly elevated temperature of 108 – 112 F.  This includes the yogurts you typically purchase at the store, and Greek and Bulgarian yogurts.  Mesophilic, by contrast, refers to yogurts that culture best at room temperature or at 68 – 78 F.  Mesophilic yogurts include viili, matsoni, piima and other styles.

How do I know my yogurt is done?

You know your yogurt is done when, after culturing it for the recommended period of time (8 to 12 hours for thermophilic yogurt, and 24 to 48 hours for room temperature yogurt), it pulls away from the sides of the jar when you tilt it.  This indicates that the proteins have coagulated and your yogurt has finished culturing.

Why is my raw milk yogurt runny?

Raw milk yogurt is runny for two reasons: 1) raw milk is rich in food enzymes and these food enzymes will continue to digest the milk and produce runny or liquid yogurt and 2) raw milk’s proteins have not been denatured through heat.  Scalding or pasteurizing milk denatures its proteins to some extent, and this allows them to be reorganized and better coagulated during the culturing process.  A runny or liquid texture is the natural state of raw milk yogurt.

Why did my homemade yogurt separate or turn lumpy?

Culturing yogurt for too long, at too high a temperature, or with an unreliable  or compromised starter culture can cause yogurt to separate or turn lumpy.  If your yogurt turns lumpy, strain it to remove the whey, then beat the yogurt solids in a bowl with a whisk until it turns smooth.  Also, make sure to culture thermophilic yogurts at temperatures of 108 to 112 F and room temperature yogurts at 68 to 78 F.  Also, make sure to use either a purchased powdered starter, or a fresh starter no older than 1 week.  After 1 week, the cultures in yogurt may deteriorate and may not be as effective at culturing milk to produce the style of yogurt you prefer.

Why is my yogurt too sour (or not sour enough)?

The hotter the temperature at which yogurt cultures, the sourer it will be.  Similarly, the longer it cultures, the sourer it will be.  In our home, I love a slow-cultured yogurt that has been cultured for 24 hours which is longer than most thermophilic yogurts; however, the typical culturing time is 8 to 12 hours.  If your yogurt is too sour, culture it at the lower range of temperatures listed for your starter, and for a shorter duration until it acquires the flavor you like.

If you like a sourer yogurt, simply culture longer until it acquires the flavor you like.  Note that, with extended culturing, it may separate or turn lumpy (see above).

Why is my yogurt foamy/stringy and why does it smell like beer/bread?

If your yogurt is foamy, stringy or smells yeasty like beer or bread, it is likely contaminated by yeast.  This can be yeast from baking, or wild yeast naturally present in your home and on your hands.  To prevent it from happening, make sure to practice good hygiene in the kitchen, using clean equipment.  Also, avoid baking yeast-based breads (including sourdoughs) on the day you make yogurt to avoid cross-contamination.

Why is my homemade yogurt grainy or gritty?

If your yogurt tastes fine, but has a weird gritty or grainy texture, this typically indicates that you heated the milk too fast. Allow the milk to come to 180 F more slowly next time.  When I make yogurt, typically 1 gallon at a time, it will take 45 minutes or longer to come to the right temperature.

Why is my homemade yogurt moldy?

Very rarely, someone experiences mold on the surface of their yogurt when making room temperature yogurts.  This can be due to a few issues: 1) poorly cleaned jars and utensils, 2) very old milk that wasn’t properly heated and then cooled down prior to culturing, 3) a compromised starter culture.  Discard the yogurt, and start fresh with a new starter and clean materials.

Can I use any milk when I make homemade yogurt?

When making traditional and room temperature yogurts, you can use any mammalian milk.  You do not need to make adjustments to the recipe, they will all perform, more or less, the same way.  Common milks include cow’s milk and goat’s milk.

If you wish to make yogurt from non-dairy milks, you will need to seek out and use a starter culture designed for non-dairy milks (like this one). Non-dairy milks will culture, but typically do not thicken like dairy-based yogurts.  To create a thick non-dairy yogurt, you will need to add gelatin, agar agar or another thickener.

Why do I have to heat pasteurized milk to make yogurt?

It may seem silly to scald pasteurized milk prior to making yogurt, but it’s effective in ensuring that you make the best quality yogurt you can.  Pasteurized milk can often become contaminated with stray microbes during packing, after pasteurization is complete.  Bringing the milk to 180 F and then cooling it down to the appropriate temperature for culturing will kill any stray microbes, ensuring the milk will not be contaminated as it cultures.

How do I make my yogurt thicker?

You can make your yogurt thicker by using whole milk, or adding cream to your whole milk yogurt.  Some home yogurt makers add milk powder, but due to its refined nature and the presence of oxidized cholesterol, this is not a solution I use in my kitchen.  You can also thicken yogurt by straining it.  To strain your yogurt, place a fine-mesh sieve (like this one) over a large mixing bowl, and line the sieve with a double layer of cheesecloth or a single layer of butter muslin (available here).  Pour the yogurt into the muslin-lined sieve, and let it sit until thickened to your liking, about 6 to 18 hours depending on how you like it.

Where to learn more about yogurt making.

Still have questions about yogurt? Want to perfect your yogurt and other homemade foods?  Check out the resources listed below:

  • Get Cultured! An online cooking class with 50+ videos devoted to *ALL* things fermented and cultured.  There’s three sections on culturing dairy, including yogurts, kefir, clabber, butter and more.  Check it out here.
  • The Art of Fermentation.  A comprehensive book on fermentation in history and the fermentation movement as a whole, with a great deal of information on yogurts and other cultured dairy products. Check it out here.