-PHOTO TAKEN 01JUL03- A worker checks on a monitor the quality of a cork stopper at the Subercentro factory in Ponte Sor, 150 km from [Lisbon] in the Portuguese Southern Province of Alentejo, in this picture taken on July 1, 2003. Portugal is the world's biggest producer of natural cork, a time-consuming business which could be squeezed out by plastic stoppers that are far easier to make and claim to preserve the taste of wine better.