158 Novel food packaging more than 70% of the limonene content in 24 hours at 25%C. However. results from gaschromatography-olfactometry (GCO) analysis indicated that limonene possessed only trace odour activity. Furthermore, the polymers did not alter the odour-active components present in orange juice Van Willige et al.(2003) investigated three types of packaging materials (LDPE, PET and PC)on flavour scalping in a model system(consisting of the compounds octanal, decanal, ethylbutyrate and 2-nonanone )and a ompletely absorbed by LDPE, followed to a lesser extent by decanal, hexylacetate, octanal and nonanone. Much less flavour compounds were absorbed by PC and PET. In contrast to LDPE valencene was absorbed to the lowest extent and decanal to the highest. From the orange juice limonene was readily absorbed by LDPE, while myrcene, valencene, pinene and decanal were absorbed in smaller quantities. Only three flavour compounds were absorbed from orange juice by PC and PET in very small amounts: limonene myrcene and decanal. Although instrumental analysis showed a substantial decrease of the flavour content between control and polymer treated sample, meaning that the polymers absorbed a substantial amount of the flavour compounds, the sensory panel was not able to detect any significant differences caused by flavour scalping. Van Willige (2002b) stated that flavour scalping is not the main reason for a possible change of flavour perception during storage of food products into polymer packaging materials It is more likely that other mechanisms play a more important role, such chemical degradation, resulting in a development of off-flavour compounds Sizer et al.(1988) stated that storage temperature remains the single most important factor in delaying flavour loss and achieving satisfactory shelf-life and quality. From all the published data, Gremli(1996) stated that there is ample evidence that flavour compounds migrate from beverages and foods into plastic packaging materials. However, investigations about the relevance of the loss of flavour compounds for the sensory quality of a product are insufficient and sometimes contradictory because flavour alteration depends on many parameters, such as storage temperature and type of packaging material Therefore, investigations regarding the effect of flavour absorption on sensory quality of a product should be carried out at ambient temperature (i.e. usual storage conditions of aseptic packs), because the rate and amount of flavour bsorption by packaging materials increases with increasing temperature(Van Willige et al, 2002a). Moreover, it is important that the polymer treated and untreated(=control) samples are comparable. That means similarly packed and using a sensory procedure that evaluates complete packaging systems with similar properties, e.g. oxygen permeability (i.e. glass-glass, and not glas laminated carton)more than 70% of the limonene content in 24 hours at 25ºC. However, results from gaschromatography-olfactometry (GCO) analysis indicated that limonene possessed only trace odour activity. Furthermore, the polymers did not alter the odour-active components present in orange juice substantially. Van Willige et al. (2003) investigated three types of packaging materials (LDPE, PET and PC) on flavour scalping in a model system (consisting of the compounds octanal, decanal, ethylbutyrate and 2-nonanone) and a reconstituted orange juice. Sensory evaluation was carried out by a sensory panel of 27 assessors. From the model system valencene was almost completely absorbed by LDPE, followed to a lesser extent by decanal, hexylacetate, octanal and nonanone. Much less flavour compounds were absorbed by PC and PET. In contrast to LDPE valencene was absorbed to the lowest extent and decanal to the highest. From the orange juice limonene was readily absorbed by LDPE, while myrcene, valencene, pinene and decanal were absorbed in smaller quantities. Only three flavour compounds were absorbed from orange juice by PC and PET in very small amounts: limonene, myrcene and decanal. Although instrumental analysis showed a substantial decrease of the flavour content between control and polymer treated sample, meaning that the polymers absorbed a substantial amount of the flavour compounds, the sensory panel was not able to detect any significant differences caused by flavour scalping. Van Willige (2002b) stated that flavour scalping is not the main reason for a possible change of flavour perception during storage of food products into polymer packaging materials. It is more likely that other mechanisms play a more important role, such as chemical degradation, resulting in a development of off-flavour compounds. Sizer et al. (1988) stated that storage temperature remains the single most important factor in delaying flavour loss and achieving satisfactory shelf-life and quality. From all the published data, Gremli (1996) stated that there is ample evidence that flavour compounds migrate from beverages and foods into plastic packaging materials. However, investigations about the relevance of the loss of flavour compounds for the sensory quality of a product are insufficient and sometimes contradictory because flavour alteration depends on many parameters, such as storage temperature and type of packaging material. Therefore, investigations regarding the effect of flavour absorption on sensory quality of a product should be carried out at ambient temperature (i.e. usual storage conditions of aseptic packs), because the rate and amount of flavour absorption by packaging materials increases with increasing temperature (Van Willige et al., 2002a). Moreover, it is important that the polymer treated and untreated (=control) samples are comparable. That means similarly packed and using a sensory procedure that evaluates complete packaging systems with similar properties, e.g. oxygen permeability (i.e. glass-glass, and not glass￾laminated carton). 158 Novel food packaging techniques