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From: Food Quality & Safety magazine, April/May 2005

Can't Stand the Heat, Get Out the TTIs

The importance of time-temperature controls is increasing in the face of more stringent regulations, new market demands and more consumer awareness. Simple time-temperature indicators (TTIs) may be the best answer.

by Bill Hartman

Storage time and temperature have historically been recognized for their effect on food quality. Perishable food products simply deteriorate more rapidly at higher temperatures. To minimize this loss of quality, it is crucial that food products be protected during storage and throughout the entire distribution path, commonly referred to as the cold chain.

The importance of time-temperature controls is increasing in the face of more stringent regulations, new market demands and more consumer awareness. Simple time-temperature indicators (TTIs) may be the best answer. TTIs are cost-effective tools that can ensure and demonstrate cold chain integrity. However, to properly leverage the benefits of temperature monitoring, the relationship between time and temperature and food quality must be better understood.

The importance of time-temperature controls is increasing in the face of more stringent regulations, new market demands and more consumer awareness. Simple time-temperature indicators (TTIs) may be the best answer.

Effective Cold-Chain Monitoring

Although temperature-monitoring tools have improved considerably from the ice cube test, the basic concept remains: Bacteria grow more rapidly on improperly stored food and this can impact food quality. Companies must manage this time-temperature relationship to ensure food distribution channels remain within adequate operating limits.

Successful food companies know the optimum storage conditions for their products. Incorporating this knowledge into food supply-chain management will help ensure that these storage temperature requirements are met. If the cold chain is compromised at any point, food quality can be compromised. Consistent and accurate temperature monitoring must be implemented.

Several methods of temperature monitoring have been developed throughout the years. From in-truck chart recorders that document trailer temperatures to retail case thermometers, the science of temperature monitoring has evolved. One new technique that has been gaining momentum is the use of simple and proven TTIs.

TTIs provide a convenient system to determine the integrity of a product’s cold chain through use of irreversible visual color changes that track the accumulative effect of temperature exposure.

The rate of color change depends on the amount of total heat energy input to the sensor. At higher temperatures, the color reaction occurs relatively quickly. As the exposure temperature drops, the reaction rate, and hence color change, slows.

Usually produced as pressure-sensitive adhesive labels, the TTIs can be somewhat customized to match the time- temperature storage requirements of specific perishable products. The reaction of the TTI must match the particular time and temperature storage curve or common spoilage rate of different foods. This will ensure that a visual change in the TTIs will correlate with a potential change in product quality. TTIs are made in a variety of formulations to account for different food spoilage rates (such as 5- 10- or 15- day shelf life for foods at 35ºF).

Properly selected TTIs can indicate remaining shelf life of a perishable product from the factory to the end-user. The TTIs accompany the products with placement on the packaging to best reflect the condition of the foods. Consumers and retailers can be satisfied by the provision of additional product quality information. TTIs can provide such a solution with convenience and reasonable costs.

Because cost-efficacy and ease-of-use are important, TTI technology is continually evolving, and at least one type now eliminates the need for indicator refrigeration prior to application thus alleviating logistical hassles.

This TTI is comprised of an indicator and an activator label. The chemical reaction will not take place until the two components are joined. This ensures that any indicator changes are a result of a compromise in cold chain integrity, and not improper indicator storage.

Importance of Food Quality

Protecting perishable seafood has always presented one of the most difficult challenges to cold chain management. Some seafood processors, in particular, have been quick to adopt quality controls on the basis of temperature and are using TTIs to track cold chain integrity.

TTIs fulfill the requirements of the recent FDA Import Alert 16-125, which details the requirements for special packaging used to extend the shelf life of fresh seafood. TTIs are utilized to approximate the time-temperature limits that could compromise the quality of fresh seafood distributed in reduced oxygen packaging (ROP). The TTIs are formulated according to the FDA predictive curve, called the Skinner-Larkin curve. This model depicts anaerobic bacteria growth in seafood over a range of times and temperatures. The progressive color changes in the selected TTIs indicate limits for shelf life and possible abuses. The results comply with regulations, meet buyer demands and protect consumers.

The growing importance of food quality is reflected in the increase in corresponding government recommendations. The USDA and FDA addressed this issue through the establishment of HACCPplans.

To meet these recommendations, food manufacturers establish these critical control points along the production and distributions lines. At each point, specific factors are measured and must be controlled within certain limits. Due to their effect on food deterioration, time and temperature are often evaluated factors. Cold chain integrity must be ensured at these points. Time-temperature monitoring throughout the distribution process is crucial in meeting HACCP standards.

The government is not the only entity putting food qualityhigh on the priority list.. Consumers are becoming more educated and are demanding that products meet higher quality standards. To satisfy consumers, retailers are placing more pressure on distributors and producers to ensure cold chain integrity.

Distributors are also faced with a changing infrastructure environment. Food processing and distribution plants are becoming smaller in number and larger in size. This creates longer distribution channels and a greater need for temperature control over lengthy periods.

The saturation of the food products industry is another factor highlighting the need to monitor temperature variations. With decreasing profit margins and heavy competition, food processors must differentiate their products. Reassuring consumers and retailers of controlled temperature storage can lead to market leadership.

Because of these issues, the food industry is increasing its focus on the relationship between time and temperature and food quality. Food companies must enhance temperature control through the entire supply chain. Therefore, it is time for the integrity of the cold chain to be demonstrated in a way that is easily discernable to retailers and consumers.


It is common knowledge that temperature abuse can cause perishable product quality issues. Increased focus on the link between temperature and food quality is calling for greater vigilance along the entire distribution line. The trend has been toward heightened government and consumer interest in food quality issues. The pressure is on food industry players to manage the integrity of the cold chain from beginning to end.

Time temperature indicators can effectively serve this purpose by helping to confirm appropriate storage temperatures. A result of the advances in temperature-monitoring technology, TTIs will become a crucial tactic in the battle to maintain quality products.

Bill Hartman is business development director, Industrial Products Division for Avery Dennison. Reach him at 440-878-7274 or



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