MAP performance under dynamic temperature conditions 565 temperature within cold stores and truckloads, there is a need to measure temperature at the level of the individual packs. Cheap versatile time temperature indicators(tTi)have been developed to give an indication of the temperature history to which individual packs have been exposed(See chapter 6). Even though these TTIs can give an indication of temperature abuse somewhere in the chain, they are not intended to reconstruct a complete temperature history and, therefore, cannot be expected perfectly to explain the resulting product quality To give an example, a TTI will not discriminate between one week's storage at 4oC disrupted by either 12 hours of continuous 12 C or six two-hour periods at 12C. However, for the packed product this might make a difference, especially as the product needs time to heat up. With 12 hours of continuous 12C th product will actually be at 12C for part of that time. Exposed to the six two- hour periods of 12C it depends on the time in between the warm periods how warm the product eventually will get. As a consequence, the two identical TTI readings from this example, can relate to two completely different qualities in the final product. Also the order of imposed temperatures will not make a difference to a TTI reading. However, for product quality, the order of the subsequent temperatures the product was exposed to might make a difference For instance, pre-climacteric fruit generally responds less vigorously to temperature than the same fruit in its climacteric stage. With the effect of temperature on fruit physiology depending on the physiological stage of the fruit, two comparable temperature profiles(in terms of the total temperature sum) can have different effects in terms of product quality as this depends on the timing of the temperature relative to the physiological development of the fruit The other important aspects of the established Ma conditions are the gas conditions, which are inextricably related to temperature. As for temperature, several indicators have been developed to monitor oxygen(O2) and carbon dioxide( CO2)in individual packages. As with TTls, these gas indicators give only an indicative value. The potential strength of the different types of indicators arises from their combined application where information on temperature and gas conditions together can give a better indication of the realised MA conditions in individual MA packs. However, defining MAP performance by the realised MA conditions in terms of temperature and gas conditions is only an indirect measure The ultimate unambiguous measure of the success of MAP is the final quality of the product. Some aspects of product quality can be related to volatile produced by the product (ethylene as a measure of ripening stage, specific volatiles produced during spoilage or anaerobic conditions, etc. ) This opens the door to adding product specific indicators to the range of indicators already available, resulting in the type of integrated freshness indicators as described in Chapter 7. Such freshness indicators might come close to giving a good evaluation of MAP performance incorporating several aspects of product qual into the equation. However, other aspects of product quality might never lend themselves to measurement in this waytemperature within cold stores and truckloads, there is a need to measure temperature at the level of the individual packs. Cheap versatile time temperature indicators (TTI) have been developed to give an indication of the temperature history to which individual packs have been exposed (See chapter 6). Even though these TTIs can give an indication of temperature abuse somewhere in the chain, they are not intended to reconstruct a complete temperature history and, therefore, cannot be expected perfectly to explain the resulting product quality. To give an example, a TTI will not discriminate between one week’s storage at 4ºC disrupted by either 12 hours of continuous 12ºC or six two-hour periods at 12ºC. However, for the packed product this might make a difference, especially as the product needs time to heat up. With 12 hours of continuous 12ºC the product will actually be at 12ºC for part of that time. Exposed to the six two￾hour periods of 12ºC it depends on the time in between the warm periods how warm the product eventually will get. As a consequence, the two identical TTI readings from this example, can relate to two completely different qualities in the final product. Also the order of imposed temperatures will not make a difference to a TTI reading. However, for product quality, the order of the subsequent temperatures the product was exposed to might make a difference. For instance, pre-climacteric fruit generally responds less vigorously to temperature than the same fruit in its climacteric stage. With the effect of temperature on fruit physiology depending on the physiological stage of the fruit, two comparable temperature profiles (in terms of the total temperature sum) can have different effects in terms of product quality as this depends on the timing of the temperature relative to the physiological development of the fruit. The other important aspects of the established MA conditions are the gas conditions, which are inextricably related to temperature. As for temperature, several indicators have been developed to monitor oxygen (O2) and carbon dioxide (CO2) in individual packages.16 As with TTIs, these gas indicators give only an indicative value. The potential strength of the different types of indicators arises from their combined application where information on temperature and gas conditions together can give a better indication of the realised MA conditions in individual MA packs. However, defining MAP performance by the realised MA conditions in terms of temperature and gas conditions is only an indirect measure. The ultimate unambiguous measure of the success of MAP is the final quality of the product. Some aspects of product quality can be related to volatiles produced by the product (ethylene as a measure of ripening stage, specific volatiles produced during spoilage or anaerobic conditions, etc.). This opens the door to adding product specific indicators to the range of indicators already available, resulting in the type of integrated freshness indicators as described in Chapter 7. Such freshness indicators might come close to giving a good evaluation of MAP performance incorporating several aspects of product quality into the equation. However, other aspects of product quality might never lend themselves to measurement in this way. MAP performance under dynamic temperature conditions 565