Safety assessment of the substance poly((R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate) for use in food contact materials

Abstract

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP Panel) assessed the safety of poly((R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate) (PHBH), CAS No 147398-31-0 and food contact material (FCM) substance No 1059. This biodegradable copolymer is produced by fermentation of palm oil using a genetically modified microorganism (Cupriavidus necator). Overall migration was up to 5.4 mg/kg. Oligomers are hydroxyl-terminated or with crotyl-and hexenyl end-groups from dehydration of hydroxyl end-groups. In the absence of calibration standards, the total oligomer migration was set at the overall migration values. Other degradation products are crotonic acid and (E)-2-hexenoic acid. Crotonic acid is authorised for use in FCMs with a specific migration limit (SML) of 0.05 mg/kg food. For (E)-2-hexenoic acid, no indication for genotoxicity was identified by the EFSA CEF Panel in its group evaluation of flavouring substances in FGE.05Rev2 (EFSA CEF Panel, 2010b). The other migrating substances detected,, are from the authorised substance ‘palm oil and/or palm fatty acid distillate’ (FCM substance No 9) used as a carbon source for the fermentation and do not give rise to safety concern. A PHBH oligomer mixture was synthesized to simulate that migrating. It did not give rise to concern for genotoxicity. From the repeated dose 90-day oral toxicity study in rats, the Panel identified the no-observed-adverse-effect level (NOAEL) at the highest dose tested in males, 1,364 mg/kg body weight (bw) per day. The Panel concluded that the potential for bioaccumulation of oligomers is low. Overall, the CEP Panel concluded that the substance PHBH is not of safety concern for the consumer if it is used alone or blended with other polymers in contact with all kinds of food during more than 6 months at room temperature or below, including hot-fill or a short heating up phase. The specific migration of all oligomers < 1,000 Da should not exceed 5 mg/kg food. The migration of crotonic acid should not exceed the SML of 0.05 mg/kg food. As the migration of (E)-2-hexenoic acid can be expected to be always lower than that of crotonic acid, no individual restriction is necessary.