Oven temperature too low
Oven temperature is always critical to good baking. Oven performance should be checked frequently to ensure correct temperature and detect hot spots.
Old batter
Batters should be used or frozen as soon after mixing as possible. Batters refrigerated longer than 48 hours will have significant loss of leavening.
Hot spots / cool spots in oven
Pans should be rotated 180° halfway through baking.
Inadequate pan greasing
Provide adequate coverage of pan release on pans before depositing batter; grease tops and cups of muffin pan. Grease only tops of pans when using paper liners.
Pans were not rotated in a convection oven
Under baking / over loading of oven
Follow package directions for proper baking temperatures and times. Fully loaded ovens reduce oven temperature in the first few minutes of baking. Bake times may need to be extended. Centers of muffins should spring back when lightly touched.
Follow package directions for proper baking temperatures. Have oven checked for accuracy using an oven thermometer.
Over baking / oven temperature too high
Follow package directions for proper baking temperatures and times. Have oven checked for accuracy using an oven thermometer.
Uneven heat
Pans should be rotated 180° after 5 -7 minutes of baking.
Deck oven is used to bake muffins
Deck ovens may provide uneven bottom heat. Place a sheet pan under the muffin tins when using a deck oven.