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Food safety just got smarter

Photonics Spectra
Apr 2009
Margaret W. Bushee, margaret.bushee@laurin.com

KINGSTON, R.I. – The hot-button issue of food contamination, it seems, is never far from the headlines, but until now, avoiding it has depended to a great extent upon the decidedly low-tech expiration date. However, thanks to technology developed by Brett Lucht and William Euler, chemists at the University of Rhode Island, soon a more fail-safe device, the smart bar code, will ensure that perishables such as meat, fish and milk are safe to consume.

SIRA Technologies of Pasadena, Calif., developed the smart bar code from the scientists’ patented discoveries related to thermochromic pigments – dyes that change color at a certain temperature – and polymers. The smart bar code will prevent a shopper from buying contaminated products, regardless of the sell-by date. It has the conventional electronic archiving function, but its ink serves as a time and temperature sensor as well.

PNBarcode_Label-pub2.jpg
The dark red rectangle on the lower part of the bar code indicates that the product is contaminated.

This innovation all started about a decade ago, when investigators at the university began studying thermochromic pigments because a cookware company wanted a polymer that could change the color of its products from red to yellow when the dishes were too hot to touch, before reverting to red. After three years of research, the scientists were successful; however, none of the 100 companies interested in the technology – for applications from health care to specialty fabrics – wanted to finance the cost of refining the polymer for its purposes.

Sweetening this outcome, however, was the unexpected finding of a polymer that changes color when heated but that does not revert to its original color – a characteristic that was just what SIRA needed. Since the 1990s, the company had been developing a bar code to sequester pathogens from animal blood by quantifying the colony with colored organic beads. Hindering this goal, however, was the fact that the pathogens continued to mutate. The technology from the University of Rhode Island allowed SIRA to develop a time- and temperature-sensitive bar code that can determine whether the conditions are favorable for pathogens.

Able to sense temperatures as low as 40°, the smart bar code can detect an accumulation of nonconsecutive readings over the time period when it is affixed to a product. For example, if milk is unsafe at 40° for a duration of three hours, three separate one-hour readings at this temperature will be sensed as three hours, activating the bar code. A previously light red rectangle on it automatically turns a deep burgundy or magenta, so the price can no longer be scanned; instead, a warning will be indicated.

According to Robert M. Goldsmith, president of SIRA, developing the technology, which was patented in 2004, into a smart bar code that is suitable for monitoring food safety and that complies with government regulations was labor-intensive and included several field trials. The company’s longer-term goal is to develop a bar code that senses temperatures as low as 0°, to safeguard frozen food.

The ink will be presented in June at the 2009 meeting of the Institute of Food Technologists in Anaheim, Calif., and distributors will be implementing the bar codes this month. Consumers can expect to see this smart technology as early as late 2009.


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