The latest entrant is the Happy Meal Project, a burger and a packet of fries that have soldiered on undecayed for 143 days. Started by New York photographer Sally Davies, as a part-art, part-food science experiment, the Happy Meal Project involves Davies documenting a Happy Meal every few days until it spoils. At day 137, the meal still looks pretty great. For its part, McDonald's has remained largely silent. The fast food giant's Chinese arm released a statement this May to counter the hysteria over Joann Bruso's year-long experiment. It announced that all its patties are made of 100 percent USDA-approved beef and are completely preservative-free. Sneakily, though, it made no mention of its fries, bread, cheese or sauce.

McDonald's French fries, for example, which have repeatedly proven their hardiness to spoilage, contain citric acid as a preservative. But a bigger factor might be the fat content of the fries. About 50 percent of the total 250 calories contained in a small order of fries come from fat. McDonald's fries are also coated in a nice, thick layer of salt, something we've been using as a natural preservative for the last 2,500 years. The beef patty is also high in fat - varying between 37 and 54 percent of the total caloric content - and has been cooked at a high temperature. "It's also very thin, which once again means high heat per surface area," says Sean O'Keefe, a professor of food science at Virginia Tech. Davies noted that over time, her patty just shrank and hardened, losing whatever moisture it once contained.

Ultimately, says O'Keefe, the McDonald's haters have gotten their science wrong. "The ingredients are similar to anything you'd see in processed fast food," he says. For better or for worse, McDonald's is no more a chemical laboratory of secret compounds designed to embalm us from the inside than any other processed food maker. A Happy Meal manages to stay unspoiled because it is fatty, salty and practically empty of nutrients - which, really, are all good reasons to avoid it anyway.