The deflated finale of your grocery store trip is finding rotten milk or rancid meat after lugging those goods up to your 5th floor walk-up (even though it clearly says right there you've got at least a day before it's supposed to be thrown out!) Well, you really shouldn't have to play roulette with grocery goods, and something called "active packaging" is on its way to help us out. Already in use in are some products like Guinesses' nitrogen-widget beer can (pictured at right), which tries to imitate the foamy head of on-tap beer. And while the beer market has been one of the main vehicles for active packaging, (they're also looking to tout the self-cooling beer can), other industries have been slower to jump on. Maybe the biggest yet-to-be tapped potential is in supermarkets to help shoppers determine food freshness. Temptime, a New Jersey company, has started selling a Time Temperature Indicator, or TTI, and supermarkets in France are already using the product in their freshest goods. TTI uses a polymerizing chemical on its bulls-eye label that tracks the temperature and sitting time, and changes color accordingly — clear to dark, with the cooler the product the slower the reaction time. And California-based Landec has developed a membrane wrapper called Intelimer that changes permeability along with temperature change, letting products "breathe" depending on how hot or cold it is. Whether these technologies will really improve upon products or just raise prices remains to be seen, but anything that eliminates moldy bread from our lives is a good thing.