I don't have the link handy, but the blog is nonaknits. She has a tip for this, that I use whenever I'm doing any kind of knitting to purling. It involves wrapping your yarn around your needle clockwise on the purl. On the following row, you will knit or purl into the back loop to "untwist" this stitch. I hope that I've explained it good enough that you can understand, or someone else here might have the link handy for that post.