Subject: Why are the lactose levels are different in whole and skim milk?

I am researching if whole milk or skim milk will sour first.  I have found 
that the bacteria in the milk turns the lactose into lactic acid which sours 
it and makes it curdle.  But I haven't found info (that I can understand) that 
explains what it is in the de-fatting process (that makes skim milk from whole 
milk)that reduces that lactose levels.  I have just found references that 
whole milk has more lactose and would then sour faster.

Re: Why are the lactose levels are different in whole and skim milk?