I'm trying to visualize what you are describing because I've never seen anything like shrinking on my boiled peanuts.
Did you boil green or dried peanuts? How long did they boil?
A photo of this shrinking and turning in would be very helpful for me to better understand the problem. I assume you are describing the peanut seeds themselves shrinking, not the shell. I just can't imagine peanuts shrinking while boiling, because they take in water as they boil and soften.
The only thing I can imagine is that you got a batch of shriveled peanuts to begin with. I've found a few shriveled, shrunken looking peanuts in my raw peanuts. Usually the shell gives a good indication that these are not good peanuts, so I remove them before boiling.
It's a good idea to inspect your raw peanuts before boiling them and remove any that don't look right. I always crack open the rejected peanuts to inspect the seeds themselves. This helps to better correlate the outer shell qualities with the peanut seeds inside them.
If you still have some of the raw peanuts from that batch, crack a few open and see how they look before boiling. Regardless, send us a picture of your shrinking, turning in peanuts to help us identify the problem.
Jan 30, 2013
Shrinking by: me
I think he is speaking of the shell caving in after the air has left it, which i have seen before myself boiling peanuts, but once you are done boiling the shell usually pops back out during the cooling and these peanuts usually draw in brine into the shell, if they haven't popped already while boiling green peanuts.