For me, "use-by" dates are mere guidelines. The contents of my fridge are a mycologist's dream. Cheese happily matures and gets a bit green around the edges (for extra flavour), lettuce flops (no longer good in a salad, but totally fine if it's blended into a soup) and half-consumed wine is left out until it turns to vinegar (that's for cooking with).
I'm oddly proud of my slatternly ways in the kitchen. I rarely throw food out, so I'm doing my bit to conserve the Earth's resources and I'm probably even responsible for creating entirely new life forms.
There's a bit of Iberico ham in a drawer somewhere that allegedly went off in October (that's October 2012), but I'm saving it for a special occasion. It's cured with plenty of food-preserving salt, so it'll probably last forever. One evening, I'll have a decadent time with my special ham and a lovely glass of Barolo. My boyfriend won't be joining me, having been put off by my suggestion we eat a perfectly good piece of beef sirloin recently. It had only been in the fridge for a week and a half, and it smelled fine, but he wasn't convinced, pointing to that pesky sell-by date, as though mere numbers on a label could support his claim. Since the incident, he's regarded my meals with a very dubious expression. On the plus side, he now offers to cook a lot more often.
Although I don't recommend that readers follow my lead, I've found that the sniff-it-and-see method of judging whether food is off is a far more accurate measure than the dates on the packet – on occasion, milk has turned green before the use-by date and even I've been forced to admit it can't be salvaged.
But now there's a new invention that can accurately tell consumers – and hoarders such as me – whether food really is past its best. It's a "smart" patch, and it was presented to the American Chemical Society (ACS) meeting in the States this week, the idea being that it changes colour depending on how much the food has deteriorated. The patch is made from futuristically named "plasmonic nanocrystals", which measure the temperature of the food over time, from production to plate. The tag sits on the outside of food packaging and will change colour from golden orange (no deterioration) to yellow (some deterioration) and finally it will appear bright green (enough bacteria to floor a rhino).
Dr Chao Zhang, the lead researcher, said: "A real advantage is that it will show you if the food has been unduly exposed to higher temperatures, which could cause unexpected spoilage." Another result is it will also save people from throwing away food because of the use-by date, when in reality the food is bacteria-free, and will keep. Waste not, want not.
Robert Martin, the head of foodborne-disease strategy at the Food Standards Agency, isn't worried that the tags will put the FSA's best-before labels out of business. "It is a legal requirement that food manufacturers label their products with an accurate best-before or use-by date," he says. But how accurate are those dates on the packet? "The use-by date relates to the safety of the food and the FSA advises people not to consume these products after this date as they could put your health at risk. Best-before dates are applied to a wide range of foods and are more about quality than safety. So when the date runs out, it doesn't mean that the food will be harmful, but it might no longer be at its best, and flavour or texture may deteriorate." See? It's just a bit of mould and loss of flavour. Nothing to worry about.
I'll definitely use the patches when they become available, just to prove to my boyfriend that the food is fine. "See, dear, the patch is yellow, so that means it's only the texture that's deteriorated." So, anyone for dinner at mine?