SORPTION OF AROMA COMPOUNDS IN PET AND PVC DURING THE STORAGE OF A STRAWBERRY SYRUP
Abstract
The sorption of 14 aroma compounds into PET and PVC was monitored during one year storage of a strawberry syrup. Their concentrations in the syrup and in the polymer were assessed during storage and compared with previously published results obtained with glass bottles. Apparent partition coefficients between the polymer and the syrup (noted Kapp) were estimated from experimental kinetics without reaching the equilibrium Kapp values were optimally identified from the kinetic data obtained between 30 and 90 days. They exhibited a similar behaviour for both polymers with values spread between 2•10-5 and 2•10-3, 4•10-5 and 3•10-2 respectively for PET and PVC. The variation of Kapp values in PET was mainly correlated to the polarity of tested compounds as assessed by their logP values. By contrast, the variations in Kapp values for PVC were mainly related to their chain lengths. Due to slightly higher partition coefficients and diffusion coefficients in PVC than in PET, the amount of absorbed aroma was 4 times higher in PVC than in PET, however the amount of absorbed aroma compounds is less than 0.1%, except for octyl butanoate, of the initial amount present into the syrup. The variation in concentration in the syrup was interpreted as a combination of a degradation process and a transport process into the packaging material. Both effects were particularly noticeable for both PETs and unstable aroma compounds.
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