This article summarizes the application and validation of a specific temperature‐time indicator (TTI) to monitor the shelf life of refrigerated salmon throughout its cold chain distribution. Reaction kinetics of the spoilage process was characterized by determining the kinetics for microbial population growth and chemical degradation (break down of nucleotides). The combined effect of these reactions on perceived organoleptic quality deterioration (appearance, odor, texture, gapping and color) was measured by a trained sensory panel. The TTI color change reaction from green to yellow was monitored with a colorimeter. The activation energies (Ea) for the spoilage reactions in the salmon and the TTI color change reaction were determined and compared for the required similarity. The color change reaction in the TTIs had Ea of 22–23 Kcal/mol, while the microbial growth and chemical degradation reactions were found to have Ea in the order of 17 and 15 Kcal/mol, respectively. Performance of the TTIs was tested under controlled constant and variable time‐temperature storage histories by comparing TTIs color change readings with sensory panel scores. Additionally, TTIs and data loggers were placed in a shipment of refrigerated salmon that traveled from Puerto Montt, Chile, to Gainesville, FL, U.S.A. via a combination of truck and air. Results showed that the TTIs used in this study with Ea of 22–23 Kcal/mol were capable of predicting the shelf life of refrigerated salmon within 10% error in cases of moderate temperature abuse (0–7C). However, TTIs with lower Ea closer to 18–19 Kcal/mol would be needed to accurately predict shelf life if product were to be subjected to more extreme temperature abuse with temperatures reaching 12–14C.
PRACTICAL APPLICATIONS
The list of products monitored by time‐temperature integrators or indicators (TTIs) has been steadily increasing, these include: fresh fruits and vegetables, fresh fish, flowers, frozen foods, dairy products, chocolates, photographic films, medical films, drugs and vaccines, cosmetics, beer, dog food, etc. TTIs can be used to monitor the distribution, and food and biological materials, and more diverse products. A tentative classification of the various applications of TTIs in food products would be:
monitoring the distribution and storage;
optimization of inventory management;
shelf‐life prediction; and
sanitary and quality prediction.
Several studies have focused on the application of indicators for frozen and chilled foods. Our studies in the evaluation of chilled fish fillets have shown that indicators can be used satisfactorily to evaluate the quality of the product during distribution. The distribution of fish is one of the areas that had the greatest potential for implementation of the TTIs.
