Influence of food matrix on absorption of flavour compounds by linear low-density polyethylene: oil and real food products

The influence of oil and food components in real food products on the absorption of four flavour compounds (limonene, decanal, linalool and ethyl 2-methyl butyrate) into linear low-density polyethylene (LLDPE) was studied using a large volume injection GC in vial extraction method. Model food systems and real food products investigated included oil/water emulsions, oil/casein models, oil/pectin models, skim milk and whole milk. A small amount of oil (50 g l-1) had a major influence on the amount of flavour absorption. Because of solubilization of the more apolar flavour compounds limonene, decanal and linalool into the oily phase, only the remaining flavour compounds in the aqueous phase were available for absorption by LLDPE. After 14 days of exposure, absorption of limonene and decanal decreased by 97°and that of linalool by 86ÐDue to a salting out effect, absorption of the less apolar ethyl 2-methylbutyrate (E2MB) first increased with increasing oil concentration, but decreased at higher oil concentrations (>2.5 g l-1). Oil/casein and oil/pectin models showed that the more apolar flavour compounds were mainly dissolved in the oily phase and that the compounds present in the aqueous phase could interact with casein or pectin. Oil influenced the level of flavour absorption by LLDPE to a much greater extent than pectin or casein. However, the low amount of fat (1.11 g l-1) in skim milk had no influence on the absorption of flavour compounds. Only the proteins in skim milk (especially casein) decreased the absorption of limonene and decanal, because the fat was probably entrapped. Whole milk, which contained a higher concentration of (free) fat, suppressed the absorption of all flavour compounds by LLDPE to the same extent as was found for the oil model solutions. In general, absorption results from skim milk and whole milk were in good agreement with the results of the investigated model solutions containing individual food components.