Diagnostic indicators for food packaging

The idea of diagnostic packaging is that the package itself or a smart indicator label attached to the package can give information about the product quality directly, about the package and its headspace gases or about the storage conditions of the package. A freshness indicator indicates the microbial quality of the product by reacting directly to the metabolites produced in the growth of micro-organisms. If perishable food products are stored above the suggested storage temperature, a rapid microbial growth takes place. The product is spoiled before the estimated "use by" -date and in the worst case growth or toxin production of pathogenic bacteria takes place. Time-temperature indicators attached on the package surface integrate the time-temperature history of the package throughout the whole distribution chain and hence give indirect information on the product quality. For many perishable products exclusion of oxygen and high concentration of CO₂ improves the stability of the product as the growth of aerobic micro-organisms is prevented. As a result of potential package leak the protecting atmosphere is deteriorated. Package leak can also increase the microbial spoilage by enabling the product contamination with harmful micro-organisms. It is possible to check the package integrity immediately after packaging procedure, but a leak indicator attached into the package gives information on the package integrity throughout the whole distribution chain. The development and testing of diagnostic indicators in confidential and non-confidential projects has been one of the key focuses of the packaging research at VTT Biotechnology for about ten years. Non-confidential research financed by European Commission, Finnish Ministry of Agriculture and Forestry, Association of Finnish Fish Retailers, National Technology Agency (Tekes) in Finland and industrial sponsors has been carried out. During these projects prototypes of leak indicators and freshness indicators especially for poultry products have been developed and tested. Related to the development of freshness indicators metabolites reflecting the quality of poultry meat have been investigated. We have also carried out projects where the already commercially available indicators have been applied for the quality control of packaged, fresh fish and poultry products. In this presentation the different types of diagnostic indicators will be briefly reviewed and examples of case studies carried out at VTT Biotechnology will be described.