Shares of Dean Foods Co.(NYSE: DF) are jumping after it was revealed that hedge fund kingpin David Tepper has purchased a sizable stake in the company.

As of 2:02 p.m. (EDT), Dean stock is up almost 8 percent.

According to an SEC filing, Tepper’s fund Appaloosa Management has acquired 7.35 percent stake in the company.

In calendar 2010, Dean plunged 52 percent, making it the worst performing stocks on the S&P 500 index.