From here: https://cooking.stackexchange.com/a/13533/6168
Overly sour yogurt is a sign of inconsistent inoculation
From: http://www.thefreedictionary.com/inoculation
The act or an instance of inoculating, especially the introduction of an antigenic substance or vaccine into the body to produce immunity to a specific disease.
What is that quote talking about? How can "inconsistent inoculation" be prevented?