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Fix / Yogurt

Troubleshooting · New on 9 October 2026

Yogurt problems and fixes

Yogurt that did not set, came out runny, grainy, too sour or full of whey: likely causes, what to change, and when to throw the batch out.

The methodRecord the batch

Most yogurt problems come from temperature: milk too hot when the starter goes in, or an incubation that drifts too cool or too warm. A thermometer solves more problems than any other tool. 31

It did not set

Discard the batch. Do not try to rescue it.

Likely causes

  • Starter without live cultures 3
  • Culture killed by milk hotter than 46 °C (115 °F) 1
  • Incubation too cool or too hot 3
  • Equipment not clean 1

What to do

  • Discard the batch; a failed set may mean unwanted microbes 1
  • Next time check the temperatures with a thermometer and use a fresh, live starter 31

Set, but thin or runny

Likely causes

  • Milk heated too little or too briefly 14
  • Milk too cool going into incubation 3
  • Goat milk, which sets softer 3

What to do

  • Hold the milk at 85–93 °C for 10–20 minutes 1
  • Add nonfat dry milk to the cold milk 4
  • Strain it for a thicker texture 3

Too sour

Likely causes

  • Incubated long after it set 1
  • A starter carried on for many batches 4

What to do

  • Refrigerate as soon as it sets 31
  • Start from a fresh culture 4

Grainy or lumpy

Likely causes

  • Incubation too hot or uneven 4
  • Slow cooling or rough handling of the set yogurt 4
  • Milk powder or sugar added to hot milk 14

What to do

  • Keep the temperature steady and chill promptly 4
  • Stir powder and sugar into the milk before heating 14

Liquid whey on top

Likely causes

  • Incubated too long or not refrigerated soon enough 31
  • Moved or stirred while setting 3
  • Milk heated too little 4

What to do

  • Some whey is natural: stir it back in or pour it off 1
  • Chill as soon as it sets and do not move it while it sets 3
  • Add milk powder next time; 5% helps prevent separation 4

Bitter, yeasty or off flavour

Likely causes

  • Milk or starter not fresh, or a contaminated culture 31
  • Unclean equipment or an uncovered container 1
  • Undesirable bacteria in the milk supply 4

What to do

  • If it smells wrong, discard it 1
  • Use fresh milk, a new culture and clean, covered equipment 1

Mould or fuzzy spots

Discard the batch. Do not try to rescue it.

Likely causes

  • Contamination from the air, equipment or starter

What to do

  • Discard the whole container; do not scrape mould off yogurt 2
  • Clean the jars thoroughly and start from a fresh culture 1

Change one thing at a time

When a batch disappoints, compare it with the method, change one variable, and note the result in a Batch Card. Two changes at once hide which one helped.

Sources

  1. University of Alaska Fairbanks Cooperative Extension: Making yogurt at home (FNH-00062)Heat to 85–93 °C (185–200 °F) for 10–20 minutes, do not boil; culture is killed above 54 °C (130 °F) and grows poorly below 37 °C (98 °F); adding culture to milk over 46 °C (115 °F) can kill it; incubate 4–7 hours at 43 °C (110 °F); sets at pH 4.6; one 5 g freeze-dried packet or ¼ cup yogurt per quart; discard batches that fail to set or show microbial growth or odd odours; keeps about 10–21 days at 4 °C. Accessed 2026-10-09.
  2. UConn Extension: Handling food with mould (citing USDA FSIS)Yogurt, sour cream and soft cheeses such as cottage and cream cheese are discarded entirely if any part is mouldy. Accessed 2026-10-09.
  3. University of Illinois Extension: Making yogurt at homeHeat milk to 82–85 °C (180–185 °F); cool to 42–46 °C (108–115 °F); 2 tablespoons of yogurt per quart of milk; incubate 6–10 hours; ready when lightly gelled like thin pudding; refrigerate at or below 4 °C (40 °F) and eat within 14 days; use homemade yogurt as starter within 5–7 days; strain 2–4 hours for Greek-style and 8–24 hours for yogurt cheese, covered in the refrigerator; troubleshooting table. Accessed 2026-10-09.
  4. University of Kentucky Cooperative Extension: Making yogurt at home (IP-36)Nonfat dry milk at 1–6%, 5% recommended against whey separation; causes of grainy texture (high or uneven incubation temperature, slow cooling, rough handling), whey separation, too much sourness and bitterness; a fresh commercial starter is recommended over carrying one culture on. Accessed 2026-10-09.

Numbers on this page come from these sources. Where sources give a range, we quote the range rather than a single figure.

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