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 absor ption of four flavour compounds (limonene, decanal, linalool and ethyl 2-me thyl butyrate) into linear low-density polyethylene (LLDPE) was studied usi ng a large volume injection GC 'in vial' extraction method. Model food syst ems and real food products investigated included oil/water emulsions, oil/c asein models, oil/pectin models, skim milk and whole milk. A small amount o f oil (50 g l(-1)) had a major influence on the amount of flavour absorptio n. Because of solubilization of the more apolar flavour compounds limonene, decanal and linalool into the oily phase, only the remaining flavour compo unds 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 86%. Due to a salting out effect, absorption of the les s 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 compou nds were mainly dissolved in the oily phase and that the compounds present in the aqueous phase could interact with casein or pectin. Oil influenced t he level of flavour absorption by LLDPE to a much greater extent than pecti n or casein. However, the low amount of fat (1.11 g l(-1)) in skim milli ha d no influence on the absorption of flavour compounds. Only the proteins in skim milk (especially casein) decreased the absorption of limonene and dec anal, because the fat was probably entrapped. Whole milk, which contained a higher concentration of (free) fat, suppressed the absorption of all flavo ur compounds by LLDPE to the same extent as was found for the oil model sol utions. In general, absorption results from skim milk and whole milk were i n good agreement with the results of the investigated model solutions conta ining individual food components. (C) 2000 Society of Chemical Industry.