Last week, I brought in an unopened mayonnaise package that had separated layers to our food lab to see if they could tell what had happened.
The content checked out, but they could not get the product emulsify back to its white state. A call was placed to the manufacturer and the manufacturer attributed the separating to freezing. The manufactureer indicated that this has been an ongoing problem with the cooler than normal temperatures. Once the product freezes, the proteins break-up and those chains cannot be put back together.