Freshness sensors gain market acceptance.

Increasingly, the food industry is faced with a dilemma as consumers desire fresh foods while changing distribution practices demand increased shelf life and the government requires safer products. Controlling a product's temperature is the primary way to maintain its quality and safety. However, abusive temperature conditions that occur when a product is stored and as it is distributed make it difficult to control its environment.

Time-temperature indicators (TTIs) are a simple way to evaluate the temperature exposure of products on a case-by-case or even package-by-package basis. A TTI is a simple, inexpensive device, usually a self-adhesive label that exhibits an irreversible measurable change in response to the cumulative effect of both time and temperature.

Tags that rely on chemical or physical reactions to indicate how temperatures may have abused processed foods have been commercially available for more than a decade. Although food manufacturers in some countries use the technology, companies based in the United States have been slow to embrace it. That is beginning to change, however, as major processors and their retail clients become more familiar with TTIs.

You activate the tags by pressing the raised areas on a strip. This causes nontoxic fluids to mix within internal pouches. A popping sound, similar to the breaking of air pockets in bubble-wrap protective packaging, indicates that an enzymatic reaction has occurred.

After activation occurs, the sensing area--a 3/8-inch dot--changes from white to green. If the time-temperature exposure of the tag surpasses a preprogrammed safe limit, the indicator dots change from green to yellow. The tags can be designed to monitor different types of perishable food products such as home meal replacement products, dairy items, meat, precut produce and seafood. In addition, you can program the tags for chilled (refrigerated) or frozen environments in time durations up to 120 days.

TTI tags mimic the process of pathogen growth in terms of both growth rate and temperature sensitivity. Thus, they can be tuned to change color when a critical safety risk point is reached. In one application, the TTI technology effectively monitored the shelf life consequences of salmon fillets during their transport and refrigerated storage. The TTI color changes simulated sensory judgments and objective measurements for product quality as influenced by constant and variable changes in product temperature. Furthermore, the tags simulated the progressive loss of quality during the storage time.

Further information. J. L. Cox, Cox Technologies Inc., 69 McAdenville Rd., Belmont, NC 28012; phone: [phone]; fax: [phone].