Confusion over date labeling leads to billions of pounds of food waste every year. Bob Brackett, PhD CFS, Director of the Institute for Food Safety and Health at the Illinois Institute of Technology and IFT spokesperson explains the difference between “use-by,” “sell-by,” and “best-by” dates.
Use-By: This label is aimed at consumers as a directive of the date by which the product should be eaten; mostly because of quality, not because the item will necessarily make you sick if eaten after the use-by date. However after the use-by date, product quality is likely to go down much faster and safety could be lessened.
Sell-By: This label is aimed at retailers, and it informs them of the date by which the product should be sold or removed from shelf life. This does not mean that the product is unsafe to consume after the date. Typically one-third of a product’s shelf-life remains after the sell-by date for the consumer to use at home.
Best-By: This is a suggestion to the consumer on which date the product should be consumed to assure for ideal quality.
Brackett also points out that smell and taste are not good indicators of whether or not a food is safe to eat.
MIT chemists have devised an inexpensive, portable sensor that can detect gases emitted by rotting meat, allowing consumers to determine whether the meat in their grocery store or refrigerator is safe to eat.
The sensor, which consists of chemically modified carbon nanotubes, could be deployed in “smart packaging” that would offer much more accurate safety information than the expiration date on the package, says Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT.
It could also cut down on food waste, he adds. “People are constantly throwing things out that probably aren’t bad,” says Swager, who is the senior author of a paper describing the new sensor this week in the journal Angewandte Chemie.
The paper’s lead author is graduate student Sophie Liu. Other authors are former lab technician Alexander Petty and postdoc Graham Sazama.
The sensor is similar to other carbon nanotube devices that Swager’s lab has developed in recent years, including one that detects the ripeness of fruit. All of these devices work on the same principle: Carbon nanotubes can be chemically modified so that their ability to carry an electric current changes in the presence of a particular gas.
In this case, the researchers modified the carbon nanotubes with metal-containing compounds called metalloporphyrins, which contain a central metal atom bound to several nitrogen-containing rings. Haemoglobin, which carries oxygen in the blood, is a metalloporphyrin with iron as the central atom.
For this sensor, the researchers used a metalloporphyrin with cobalt at its centre. Metalloporphyrins are very good at binding to nitrogen-containing compounds called amines. Of particular interest to the researchers were the so-called biogenic amines, such as putrescine and cadaverine, which are produced by decaying meat.
When the cobalt-containing porphyrin binds to any of these amines, it increases the electrical resistance of the carbon nanotube, which can be easily measured.
“We use these porphyrins to fabricate a very simple device where we apply a potential across the device and then monitor the current. When the device encounters amines, which are markers of decaying meat, the current of the device will become lower,” Liu says.
In this study, the researchers tested the sensor on four types of meat: pork, chicken, cod, and salmon. They found that when refrigerated, all four types stayed fresh over four days. Left unrefrigerated, the samples all decayed, but at varying rates.
There are other sensors that can detect the signs of decaying meat, but they are usually large and expensive instruments that require expertise to operate. “The advantage we have is these are the cheapest, smallest, easiest-to-manufacture sensors,” Swager says.
The new device also requires very little power and could be incorporated into a wireless platform Swager’s lab recently developed that allows a regular smartphone to read output from carbon nanotube sensors such as this one.
The researchers have filed for a patent on the technology and hope to license it for commercial development.