Is your raw milk yogurt runny? Does your homemade yogurt separate? Is it foamy? Too sour? Too liquid? Not sour enough? 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.
Jump to Basics | Flavor | Texture | Other Problems
Yogurt-Making Basics
Every society that raises animals for milk has a recipe for yogurt. These recipes vary from region to region, and their flavor is influenced by the milk they use, how long they culture that milk, and the starter culture (if any) people add to the milk. As a result, there are many different varieties of cultured dairy foods.
Making Yogurt
Making yogurt and other fermented and cultured milk products is simple. It typically involves mixing fresh milk with a starter culture and allowing that milk to sit until thickened and sour. Sometimes, cooks will strain the yogurt to provide a thicker consistency.
- You can make yogurt with raw milk, and you can also make homemade yogurt from pasteurized or scalded milk.
- Your starter culture contains bacteria that transform the milk into yogurt.
- Some of these bacteria benefit from consistently elevated temperatures (108 - 112 F), and these are referred to as thermophilic (heat-loving) yogurt. Greek and Bulgarian yogurts are good examples.
- Some of these bacteria benefit from lower, room temperatures of about 65-78 F. These are referred to as mesophilic and include room-temperature cultured dairy foods such as matsoni or milk kefir.
- The time required to make yogurt and similar cultured dairy foods varies from about 6 hours on the low end to 48 hours on the high end.
How do I know my yogurt is done?
You know your yogurt is done when, after culturing it for the recommended period of time (6 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.
Problems with Yogurt's Flavor
Sometimes your yogurt just doesn't taste quite right. Often, this is because of your personal preference and expectations. For this reason, most problems with yogurt's flavor can be easily remedied by making small changes to the culturing process.
Rarely, there may be a problem with your starter culture. And, if that's the case, discarding your starter and beginning again is the best remedy.
Why is my yogurt too sour?
Both temperature and time influence how sour yogurt will taste. That's because as yogurt cultures, the bacteria in the starter culture will eat the naturally occurring milk sugar (lactose) and release lactic acid. The acid they release makes the yogurt taste sour.
- Culturing yogurt for too long or too high a temperature can make it taste extra sour.
- Most homemade yogurts are thermophilic. This includes popular options such as Bulgarian and Greek yogurt. Culture them at 108 - 110 F for about 6 hours for a mildly sour yogurt.
- For room temperature yogurts, such as matsoni, culture the yogurt at room temperature for about 24 hours.
Why isn't my yogurt sour enough (or sour at all)?
Time and temperature influence how sour your yogurt will be. If your yogurt isn't sour enough, try culturing it longer or at a slightly higher temperature.
- Increase time or temperature. The longer your yogurt cultures, the sourer it will be. For brightly sour yogurt, try culturing it beween 110 - 112 F for 8 to 12 hours.
- Sometimes yogurt will thicken but never taste sour. So, if you've cultured your yogurt at the recommended time and temperature, and it's thick and doesn't taste sour at all, you have a damaged starter. Discard your starter and acquire a new one. Then start the process over.
Why does my yogurt taste weird or bad?
Homemade yogurt and similar cultured dairy foods should taste pleasantly sour. So a sour flavor (more or less pronounced) is normal.
- If your yogurt tastes weird, bad, putrid, or otherwise off-putting, it's because of microbial imbalance in your starter and potential cross-contamination. Often this happens because the yogurt or starter is expired or too old.
- Discard any bad- or weird-tasting yogurt and your starter culture. Get a fresh starter as well as fresh milk, and then start over.
Problems with Yogurt Texture
Sometimes your yogurt may taste fine, but the texture is strange. The most common problem is that yogurt is runny. Sometimes, yogurt can also be stringy, viscous, fizzy or carbonated, gritty, or curdled.
Some of these issues are easily fixed by changing your ingredients or technique. However, most issues with yogurt texture are a problem not with technique, but with the quality of your starter. For those, you'll need to start over.
Why is my yogurt runny?
There are a few reasons why your yogurt might be runny. Yogurts made with raw milk are naturally runny due to both food enzymes and the milk's protein structure. In addition, yogurts made with pasteurized milk can be runny due to an old starter or culturing the yogurt at the wrong temperature or for the wrong length of time.
If you're using raw milk:
- Raw milk yogurt is naturally runny. That's because it's rich in food enzymes which can contribute to a runny texture.
- Raw milk yogurt hasn't been heated and its proteins don't coagulate well. Scalding or pasteurizing milk denatures its proteins, 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.
- To thicken raw milk yogurt that's too runny, consider straining it or adding a thickening agent such as pectin or gelatin. Some people have success by adding powdered milk.
If you're using pasteurized milk:
- Too little starter culture can make yogurt runny. Try using ¼ cup starter to 1 quart of milk. If you're using a powdered starter, follow the instructions of the package.
- Cold temperatures and too little time can mean your yogurt stays runny. Try culturing your yogurt for at least 6 hours and up to 12 hours at 108 to 112 F.
- If it doesn't thicken and doesn't turn sour, your starter might be dead or expired. Discard this batch and start over with fresh milk and a fresh starter.
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 your 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.
Other causes of lumpy yogurt:
- Pay attention to temperature. Culture thermophilic yogurts at temperatures of 108 to 112 F and room temperature yogurts at 68 to 78 F.
- Keep your starter fresh. 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.
- Using a starter culture that contains additives or thickeners (which are often found in store-bought yogurts) can create off-textures.
- Disturbing your yogurt while it ferments can also cause lumpiness. Yogurt cultures best in a still environment, and agitating, bumping, stirring, and moving your yogurt during this process may cause lumpiness.
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 yeasted bread (including your favorite sourdough recipes) on the day you make yogurt to avoid cross-contamination.
Other ways yogurt can be contaminated by yeast:
- Brewing yeasted beverages at the same time as you make yogurt can create cross-contamination. So avoid brewing homemade beers, kombucha, jun, ginger bug, vinegar, and water kefir at the same time you make yogurt.
- Baking at the same time as making yogurt can cause cross-contamination.
- Using contaminated materials, such as a wooden spoon you've used to mix yeasted bread can cause cross-contamination - even if you've washed it.
- Fermenting yogurt and fruit together can create off-flavors, so only add fruit to plain yogurt after it's finished culturing.
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. It can take upwards of 45 minutes to bring a gallon of milk to 180 F.
Other reasons your yogurt might be gritty:
- Heating milk too quickly is the biggest culprit behind gritty yogurt. So, try heating it more slowly.
- A compromised starter culture can also cause your yogurt to be gritty. Many store-bought yogurts contain additives and thickeners, which can cause yogurt to turn gritty, lumpy, or grainy. Use an heirloom starter or plain store-bought yogurt that contains only live cultures and milk (no additives, thickeners, food starch, inulin, etc.)
- Failure to mix your starter thoroughly into your milk can also cause it to be gritty.
Why is my yogurt curdled?
As with gritty and lumpy yogurt, sometimes yogurt will take on a curdled appearance. This is most likely due to culturing yogurt for too long or at too high of a temperature.
Other reasons your yogurt might curdle:
- Culturing yogurt for too long will cause it to curdle before it separates into curds and whey. Try culturing your yogurt at a slightly lower temperature or for less time.
- A starter culture that contains additives or thickeners can cause it to curdle. So use a powdered heirloom starter or fresh, additive-free plain yogurt from the store that contains nothing but live cultures and milk.
- Too high of a temperature can cause your yogurt to curdle, so pay attention to temperature. The optimal temperature for most homemade yogurts is 108-112 F.
Why is my yogurt watery or separated?
Yogurt can become watery when the whey separates from the milk solids (or curds). Many factors can contribute to separated, watery yogurt, but the biggest and most likely culprit is over-culturing.
- Culturing yogurt at too high a temperature can cause it to separate. You may also notice an intensely sour flavor or lumpy texture. It's safe to eat, but you may want to run it through a blender first to improve its texture.
- Very old yogurt will also separate and become watery. If your yogurt has been in your fridge for a while and is separated, it's best to discard it as it's likely past its prime.
Other problems you might see
Most problems you'll face when making yogurt at home have to do with its flavor and texture. Further, most of these issues are resolved by paying careful attention to the quality and freshness of your starter, the cleanliness of your work area, as well as time and temperature.
Occasionally, other issues arise. Perhaps your yogurt simply didn't culture at all, or maybe you've noticed spots of mold.
Why is my homemade yogurt moldy?
Very rarely, you may see mold on the surface of their yogurt. This can be due to a few issues. Poorly cleaned jars and utensils, old milk, improper handling, and a compromised starter culture are the biggest culprits. If you see mold, discard the yogurt, and start fresh with a new starter and clean materials.
- Use clean utensils and jars to prevent stray microbes from contaminating your yogurt. This practice helps not only with mold but also yeast.
- Use fresh milk. Old, expired milk can give yogurt a strange, unpleasant flavor and leave it open to contamination by mold.
- Room-temperature yogurts are more likely to mold than those cultured at elevated temperatures.
- Old starter culture can contribute to mold in yogurt. The beneficial bacteria in your starter culture will weaken with prolonged storage, meaning they may not effectively acidify the milk, resulting in contamination by mold. Make yogurt every 7-10 days to keep your starter culture healthy.
- Discard any moldy yogurt or starter, and start fresh.
Why is my yogurt fizzy?
Occasionally your yogurt might have a fizzy quality when opened or it may taste carbonated. Fizzy yogurt is usually a result of contamination by yeast. It's best to discard the yogurt, your starter, and begin with fresh ingredients.
Nothing happened when you tried to make yogurt.
Occasionally your yogurt may not culture at all. You may follow all the instructions, use clean materials and fresh milk, and, still, nothing happens. If you follow the instructions and nothing happens, your starter culture is dead.
- If you purchased a commercial, heirloom culture, let the manufacturer know that it was dead and ask for a refund. This is rare, but it does happen.
- If you purchased a plain yogurt from the store to act as a starter, discard the starter and the milk and try either a new starter or buy a commercial, heirloom starter which tend to have a better success rate.
- If you used your own yogurt from a previous batch as a starter, it was probably too old. Discard it and the milk, and then start fresh with a new, purchased starter.
