Why is the fermentation not starting in the recommended time?
The most common causes are oxygen limitation and temperature. Low dissolved oxygen levels may cause a long lag at the start of fermentation. Oxygen is a primary element needed for yeast to be able to produce cell walls. Temperature of the wort when the yeast is pitched is also critical. If the wort is above 85-90°F, this may decrease the cell viability. If the wort is too cold it can cause the yeast to slow down, therefore increasing the overall time needed for fermentation to start.
