Smart Tag Flags Spoiled Food & Meds

A color-coded smart tag could tell consumers whether a carton of milk has turned sour or a can of green beans has spoiled without opening the containers, according to researchers at Peking University in Beijing, China. The tag, which would appear on the packaging, also could be used to determine if medications and other perishable products were still active or fresh. The report on the color-changing food deterioration tags was presented on March 17th 2014 as part of the 247th National Meeting & Exposition of the American Chemical Society in Dallas.

A release from the society quotes lead researcher Chao Zhang, Ph.D. as saying, "This tag, which has a gel-like consistency, is really inexpensive and safe, and can be widely programmed to mimic almost all ambient-temperature deterioration processes in foods." Zhang added that use of the tags could potentially solve the problem of knowing how fresh packaged, perishable foods remain over time and that a real advantage is that even when manufacturers, grocery-store owners and consumers do not know if the food has been unduly exposed to higher temperatures, which could cause unexpected spoilage, "the tag still gives a reliable indication of the quality of the product."

The release explains that the tags, which are about the size of a kernel of corn, would appear in various color codes on packaging. "In our configuration, red, or reddish orange, would mean fresh," Zhang said. "Over time, the tag changes its color to orange, yellow and later green, which indicates the food is spoiled." The colors signify a range between 100 percent fresh and 100 percent spoiled. For example, if the label says that the product should remain fresh for 14 days under refrigeration, but the tag is now orange, it means that the product is only roughly half as fresh. In that case, the consumer would know the product is edible for only another seven days if kept refrigerated.

The researchers developed and tested the tags using E. coli, food-spoiling bacteria that cause gastrointestinal problems, in milk as a reference model. "We successfully synchronized, at multiple temperatures, the chemical evolution process in the smart tag with microbial growth processes in the milk," Zhang said. The tags could also be customized for a variety of other foods and beverages.

A video, illustrating how the tag works, is available at

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