Effect of relative humidity on the desorption of odour-active volatile organic compounds from paper and board: sensory evaluation and migration to Tenax®

Paper and board are used for packaging of moist as well as dry food. According to Regulation (EC) No. 1935/2004, food contact materials (FCM) must not bring about a deterioration in the organoleptic characteristics of foodstuffs. For testing the transfer of off-flavour (taint) from packaging to food via the gas phase (DIN EN 1230-2), relative humidity (rH) has to be adjusted. In contrast, rH is neither taken into account when testing the odour (DIN EN 1230-1), nor in chemical migration of volatile organic substances (VOC) onto the adsorbent Tenax^® (DIN EN 14338). In this work, effect of different rHs on the desorption of VOC from paper and board was investigated by GC-MS analysis as well as by human sensory tests. Raising humidity led to an increase in VOC transfer, which was observed by increasing peak areas as well as the detection of more substances in GC-MS. Analytical results were in line with human sensory tests. The odour profile of the paper at 33 and 58% rH was described as cardboard-like, sweet and smoky. Impact substances for these olfactory impressions were (E)-2-nonenal, vanillin and 2-methoxyphenol as identified by GC with an olfactory detection port (GC-ODP). The increase to 75 and 100% rH resulted in the additional perception of cheesy/sweaty and fatty/rancid impressions, which were primarily caused by short-chain fatty acids and di-unsaturated aldehydes.