Research on tags that are applied to the exterior case of a product and change color as food deteriorates was presented at the National Meeting and Exposition of the American Chemical Society (ACS). ACS is the world’s largest scientific society. The convention, featuring 10,000 reports was attended by thousands of scientists and is being held at the Dallas Convention Center and hotels through March 19, 2014. One of the products featured during the meetings was a smart tag that turns color when food goes bad. The deterioration tag is activated when placed on a food product and turns a specific shade when the food inside the container is spoiled.
Currently, the gel-like square attaches to the outside of each container and monitors the levels of temperature deterioration and subsequent freshness. It would conceivably be helpful not only for end-consumers but also for store owners to determine if the product may have been exposed to higher than normal temperatures which may accelerate product spoilage. Therefore, without opening a product’s packaging, the tag will provide a reliable indication of the freshness quality of the food inside.
The smart tag may be useful not only as a color indication of when food goes bad, but could also be used to tell when other perishable products such as medications spoil. According to Chao Zhang, Ph.D., the tags can be customized for other beverages and a variety of foods. The current color configuration begins with fresh food having a tag indication of red which gradually changes through a spectrum of orange, then yellow, and finally green when the product is spoiled.
The tags were tested on milk after being developed for E. coli as a reference model. According to researchers, the tags were successfully used at a variety of temperatures to correctly determine the chemical processes and microbial growth in the milk. According to Zhang, the tags are approximately the size of a corn kernel.
The tags work because they contain tiny metallic nanorods that can display different colors depending on phases and stages of the product. The research utilized gold nanorods which are inherently red and as such, dictate the initial color of the tag. Included in the tags are small amounts of vitamin C and silver chloride which react both controllably and slowly. As time passes, the silver deteriorates onto the gold nanorods which begin to form a silver layer. The silver layer changes both the chemical composition and the shape of the particle so it allows the tag to begin a color change. As the silver layer increases and thickens, the color progresses through a set series of colors. At this time, it evolves from red to orange, then yellow, green, and eventually to blue and violet.
One of the major concerns of consumers would be the price of the tags. Although the nanorods are made up of both gold and silver, the tag is inexpensive. The projected price at this time is for each individual tag to cost considerably less than one cent, or $0.002 to be more precise. Additionally, the tags are nontoxic and some of the elements, such as the vitamin C, are even edible.
These tags are currently patented in China with preliminary results having been published in ACS Nano. The next step for the company and the product is to market the idea and convince both customers and manufacturers of the usefulness of a smart tag that will turn color when food goes bad.
By Dee Mueller