Diffusion behaviour of the acetaldehyde scavenger 2-aminobenzamide in polyethylene terephthalate for beverage bottles

摘要

class="head no_bottom_margin" id="S0001title">IntroductionPolyethylene terephthalate (PET) bottles are widely used as packaging material for natural mineral water, soft drinks and juices. PET is a transparent packaging polymer that is virtually unbreakable. This unbreakable nature of PET is an important feature for a beverage packaging that permits the safe handling of bottled water (e.g., at home or during sports) compared with competitive glass bottles. The global usage volume of PET packaging was almost 16 million metric tons in 2013. A total of 36% of this PET material was used for the manufacturing of mineral water bottles (Welle ). In comparison with glass bottles, which release only inorganic compounds (Reimann et al. , ), the migration of organic compounds from the PET bottle wall into bottled mineral water plays an important role. For example, during PET bottle manufacture, acetaldehyde can be generated and might migrate into PET bottled natural mineral water. According to European Regulation No. 10/2011, the specific migration of acetaldehyde into PET packed food is restricted to a specific migration limit (SML) of 6 mg kg^–1 food (EU ). This SML cannot be reached under typical storage conditions of PET bottles (Welle ). However, the organoleptic properties of the PET packed mineral water might be influenced due to acetaldehyde migration. The taste threshold of acetaldehyde in water is between 10 µg l^–1 (retronasal) and 25 µg l^–1 (orthonasal) (Buettner & Schieberle ). Such low concentrations of acetaldehyde in natural mineral water lead to an off-taste. In consequence, the packaging material is not in compliance with Article 3 of European Framework Regulation No. 1935/2004 (EU ) or the US Federal Food, Drug, and Cosmetic Act (USFDA ). Both regulations demand in general that the organoleptic properties of packed food should not be influenced by the packaging material. Therefore, migration of acetaldehyde into food is relevant for natural mineral water due to possible organoleptic complaints. Modern PET manufacturing practices have been used to minimise the formation of aldehydes during pre-form and bottle manufacturing. However, trace levels of acetaldehyde are found in PET bottles, which can still migrate into natural mineral water during the shelf life of 6–12 months. The migration of acetaldehyde into natural mineral water follows Fickian laws of diffusion (Ewender et al. ). A correlation between bottle wall concentration and migration after storage for 10 days at 40°C has been established (Welle ).According to migration theory, the migration of an organic compound in the packaging polymer correlates directly with the bottle wall concentration (Crank ). Therefore, the main strategy to reduce the migration of acetaldehyde into natural mineral water is to minimise the concentration of acetaldehyde in the PET bottle wall. Lower bottle wall concentrations of acetaldehyde lead to lower migration into mineral water. 2-Aminobenzamide (CAS No. 88-68-6; anthranilamide) is widely used as a scavenging agent for acetaldehyde during PET pre-form production in order to reduce the concentration of acetaldehyde in the PET bottle wall. shows the proposed mechanism of the reaction between 2-aminobenzamide and acetaldehyde during pre-form manufacturing (Mrozinski et al. , ). class="figpopup" href="/pmc/articles/PMC4784489/figure/F0001/" target="figure" rid-figpopup="F0001" rid-ob="ob-F0001">Figure 1. Mechanism of the reaction of 2-aminobenzamide with acetaldehyde during PET pre-form manufacturing.