Extensive customer research assured Pennsylvania's Wawa Dairy that a switch to PET from high density polyethylene (HDPE) for single-serve juices and teas would positively impact sales. Still, summer's 30 percent spurt raised eyebrows.

The dairy is a captive supplier to Wawa Inc.'s 500-plus convenience stores in Philadelphia and south to Virginia. The fast-growing retail chain would have sold more juice on the strength of new stores alone last summer, but managers say the higher quality packaging also played a role. A Federal filler will be installed in the coming months to handle PET and HDPE pints, the dairy's fastest growing drink size. Research indicated consumers expect to find milk products in HDPE, so PET is not being used to package pints of milk.

Distinctive packaging is a priority, and the company isn't shy about paying a premium if consumer research supports a change. A patented square bottle is used for half-gallon drinks, for example. The heavy-duty, grippable unit weighs 72 grams, about 30 grams heavier than conventional HDPE half gallons.