TheStreet's Jim Cramer says Tyson Foods' bid for Hillshire Farms is all about "critical mass" in supermarkets. When food companies like Tyson are up against large supermarket chains like Safeway and Kroger, they need to be able to fight for premium space and displays for their products. Cramer thinks this is what is driving deals in the food and beverage space. Cramer says investors should watch Pinnacle Foods because it's a good company with a nice yield, and it seems to have gotten lost in the shuffle of recent M&A deals. Cramer likes Pinnacle's stock because it is too low, but on the other hand, Cramer thinks Hillshire Farms stock is too high and investors shouldn't chase it at this point.