Without actually smelling a milk carton, it can be difficult to tell whether the milk in your fridge has gone bad. And since smelling soured milk is anything but an enjoyable experience, Chinese scientists have come up with a "smart tag" that can monitor the freshness of milk.
The new "smart tags" were unveiled at the recent American Chemical Society's (ACS) National Meeting that was held in Dallas, Texas. Using a combination of nano-materials, enzymes and agar, the scientists were able to create a gel-like substance that could be used as tags in milk products and quite possibly, other perishable products as well.
The tiny gel cubes were conceptualized and created by a team of scientists from Beijing's Peking University. The team was spearheaded by the lead researchers Chao Zhang, also from the Peking University.
"Food safety is a constant concern for humans. Besides adulteration and contamination, another major threat comes from the spontaneous spoilage of perishable products, which is basically inevitable and highly dependent on the temperature history during the custody chain," said Zhang and his colleagues. "For advanced quality control and assessment, time-temperature indicators (TTIs) can be deployed to document the temperature history.
The tags were made using a variety of materials and substances including lactic acid, acetic acid, vitamin C, agar and tiny compounds made out of silver and gold called nanorods. The substance can change color to reflect the freshness of the milk inside a carton. For fresh, unspoiled milk, the tags will show a red color. Over time, the tags change color to orange, yellow and finally green depending on the freshness of the product. Green means that the milk is spoiled and no longer suitable for consumption.
Similar concepts and ideas have been around for years. However, other food freshness indicators are often expensive to produce making them impractical for use in disposable food containers. The new "smart tags" created by Zhang and his team are very affordable and easy to manufacture.
While the "smart tags" were only recently unveiled at the ACS meeting, the foundation used to create the tags was published in April 2013 in the scientific journal ACS Nano.
"We present proof-of-principle demonstrations that our TTI can be specifically tailored and thus used to track perishables, dynamically mimic the deteriorative processes therein, and indicate product quality through sharp-contrast multicolor changes," said the study's authors. "The flexible programmability of our TTI, combined with its substantially low cost and low toxicity, promises a general applicability to each single packaged item of a plethora of perishable products."
