150 Novel food packaging techniques TEMPERATURE STORAGE TIME FOOD MATRIX POLYMER FLAVOUR RYSTALLINITY MOLECULAR SIZE ABSORPTION POLARITY POLARITY AFFINITY Fig8.3 Factors influencing flavour absorption by plastic polymers (Van Willige watery phase, which could be responsible for the decrease of absorption of these compounds by the plastics Fukamachi et al. (1996) studied the absorption behaviour of flavour compounds from an ethanolic solution as a model of alcoholic beverages. The absorption of a mixture of homologous volatile compounds(esters, aldehydes and alcohols with carbon chain length 4-12)into LDPE film first increased with a maximal absorption at 5-10%(/v)aqueous ethanol and then decreased remarkably with increasing ethanol concentration. EVOH film showed similar absorption behaviour, with maximal absorption at 10-20%(v/v) aqueous ethanol. Nielsen et al. (1992) investigated the effects of olive oil on flavour absorption into LDPE. Olive oil and, thereby, the flavours dissolved in the oil were absorbed in large amounts by the plastic. The partition coefficients for alcohols and short-chained esters in an oil/polymer system were higher than in a water/polymer system, while the partition coefficients for aldehydes and long- ined esters were lower in an oil/polymer system than in a water/polymer rstem. Not only the type of plastic used is of importance for the uptake of aroma compounds, but also possible interactions between flavour and food components. Flavour components may be dissolved, adsorbed, bound entrapped, encapsulated or retarded in their diffusion through the matrix by food components. The relative importance of each of these mechanisms varies with the properties of the flavour chemical(functional groups, molecular size shape, volatility, etc )and the physical and chemical properties of the components in the food(Kinsella, 1989, Le Thanh et al. 1992) Knowledge of the binding behaviour of flavour components to non-volatile food components and their partitioning between different phases(food omponent/water and water/polymer) is of great importance in estimating the rate and amount of absorption by polymers. Because many food products are emulsions of fat and water, such as milk and milk products, the fat content is an important variable in the food matrix. Fat/oil content is often reduced in order towatery phase, which could be responsible for the decrease of absorption of these compounds by the plastics. Fukamachi et al. (1996) studied the absorption behaviour of flavour compounds from an ethanolic solution as a model of alcoholic beverages. The absorption of a mixture of homologous volatile compounds (esters, aldehydes and alcohols with carbon chain length 4-12) into LDPE film first increased with a maximal absorption at 5–10% (v/v) aqueous ethanol and then decreased remarkably with increasing ethanol concentration. EVOH film showed similar absorption behaviour, with maximal absorption at 10–20% (v/v) aqueous ethanol. Nielsen et al. (1992) investigated the effects of olive oil on flavour absorption into LDPE. Olive oil and, thereby, the flavours dissolved in the oil, were absorbed in large amounts by the plastic. The partition coefficients for alcohols and short-chained esters in an oil/polymer system were higher than in a water/polymer system, while the partition coefficients for aldehydes and long￾chained esters were lower in an oil/polymer system than in a water/polymer system. Not only the type of plastic used is of importance for the uptake of aroma compounds, but also possible interactions between flavour and food components. Flavour components may be dissolved, adsorbed, bound, entrapped, encapsulated or retarded in their diffusion through the matrix by food components. The relative importance of each of these mechanisms varies with the properties of the flavour chemical (functional groups, molecular size, shape, volatility, etc.) and the physical and chemical properties of the components in the food (Kinsella, 1989; Le Thanh et al. 1992). Knowledge of the binding behaviour of flavour components to non-volatile food components and their partitioning between different phases (food component/water and water/polymer) is of great importance in estimating the rate and amount of absorption by polymers. Because many food products are emulsions of fat and water, such as milk and milk products, the fat content is an important variable in the food matrix. Fat/oil content is often reduced in order to Fig. 8.3 Factors influencing flavour absorption by plastic polymers (Van Willige, 2002c). 150 Novel food packaging techniques