McCain Foods is blaming a shift in the market for French fries and the stronger Canadian dollar for its decision to close a plant in Prince Edward Island. When the plant in Borden-Carleton shuts down at the end of October, 121 jobs will be lost. The company said Thursday there has been a shift in demand for its French fries from North America to other parts of the world, which was a factor in its decision. The New Brunswick-based food company says production at its plant in P.E.I. has dropped by two-thirds over the last decade and it’s now the smallest and least utilized factory in McCain’s network of facilities across North America.