282 Novel food packaging techniques modified-atmosphere package because the Oz-absorbing component with adjusted capacity for the residual O2 is included in the indicator and, moreover the indicator is included in a film composition which protects against oxidation of the indicator during packaging 13.4.4 Carbon dioxide indicators CO2 is widely used as a protective gas in modified-atmosphere packaging During the first 12 days after the packaging procedure CO2 is dissolved into the product and its concentration in the head-space is decreased, the final concentration being even as low as half of the original. After this period (1-2 days)a considerable decrease in CO2 concentration is an evident sign of leakage in a package. However, CO2 is also produced in microbial metabolism and its accumulation in a package headspace can be considered to be a sign of microbial growth. A leak in a package( decrease in the CO2)is often followed by microbial growth (increase in the CO2)and, in the worst case, the CO2 will remain constant even in the case of leakage and microbial spoilage. For these two reasons, CO2 indicators as leak indicators appear not to be as reliable as O2 indicators In their patent Balderson Whitwood"o describe a reversible CO2 indicator suitable for modified atmosphere packages. The indicator consists of, for example, five indicator strips. The strips contain CO2-sensitive indicator material consisting, for example, of an indicator anion and a lipophilic organic quaternary cation. +/The colour change of each strip has been designed to take place when the CO2 concentration is below a certain limit(e.g. 25%, 20%, 15%, 10% or 5%). The concentration of CO2 is indicated by a change of colour in one or more of the strips. Sealed Air Ltd has produced a visible CO2 indicator for MAPs 13.4.5 Safety aspects A self-evident requirement for internal indicators placed in the package headspace is their absolute safety. The legislative aspects are discussed in Chapters 19 and 22. 13.5 Future trends Package integrity is an essential requirement for maintaining the high quality of e.g., sterilised and modified atmosphere packaged foods. The increasing focus on quality assurance is putting demands on verification of food package and seal grity. On the other hand, much effort is and will also be put into the development of new materials and packaging systems with minimised risk of cage failur Non-destructive package leak detection systems installed in-line are not yet very widely used, mainly because of high costs and lack of reliability/sensitivitymodified-atmosphere package because the O2-absorbing component with adjusted capacity for the residual O2 is included in the indicator and, moreover, the indicator is included in a film composition which protects against oxidation of the indicator during packaging. 13.4.4 Carbon dioxide indicators CO2 is widely used as a protective gas in modified-atmosphere packaging. During the first 12 days after the packaging procedure CO2 is dissolved into the product and its concentration in the head-space is decreased, the final concentration being even as low as half of the original. After this period (1–2 days) a considerable decrease in CO2 concentration is an evident sign of leakage in a package. However, CO2 is also produced in microbial metabolism and its accumulation in a package headspace can be considered to be a sign of microbial growth. A leak in a package (decrease in the CO2) is often followed by microbial growth (increase in the CO2) and, in the worst case, the CO2 will remain constant even in the case of leakage and microbial spoilage. For these two reasons, CO2 indicators as leak indicators appear not to be as reliable as O2 indicators. In their patent Balderson & Whitwood44–46 describe a reversible CO2 indicator suitable for modified atmosphere packages. The indicator consists of, for example, five indicator strips. The strips contain CO2-sensitive indicator material consisting, for example, of an indicator anion and a lipophilic organic quaternary cation.47 The colour change of each strip has been designed to take place when the CO2 concentration is below a certain limit (e.g. 25%, 20%, 15%, 10% or 5%). The concentration of CO2 is indicated by a change of colour in one or more of the strips. Sealed Air Ltd has produced a visible CO2 indicator for MAPs. 13.4.5 Safety aspects A self-evident requirement for internal indicators placed in the package headspace is their absolute safety. The legislative aspects are discussed in Chapters 19 and 22. 13.5 Future trends Package integrity is an essential requirement for maintaining the high quality of, e.g., sterilised and modified atmosphere packaged foods. The increasing focus on quality assurance is putting demands on verification of food package and seal integrity. On the other hand, much effort is and will also be put into the development of new materials and packaging systems with minimised risk of package failures. Non-destructive package leak detection systems installed in-line are not yet very widely used, mainly because of high costs and lack of reliability/sensitivity 282 Novel food packaging techniques