Changes

A: You should if your commercial blend is nearing it's expiration date or wasn't handled properly, or if your batch size is much larger than the intended pitch rate. Otherwise a starter isn't necessary. It is often stated that making a starter may alter the proportions of the various organisms included in the blend. This may be true and it may or may not effect the flavor profile of the resulting beer but having an underpitch of unhealthy cells is a worse approach. Changing proportions is less likely with blends consisting of a single type of organism. While some yeast labs say not to make a starter for mixed cultures, others advise that it is perfectly fine. See [[Mixed_Cultures#The_Yeast_Bay_on_M.C3.A9lange_and_Farmhouse_Sour_AleStarters_and_Other_Manufacturer_Tips|advice from Yeast Bay]] as an example of how to make a starter for a commercial blend.