Decontamination efficiency of poly(hydroxybutyrate-co-valerate)-based food packaging material: The role of the chemical structure of contaminants and additive

Recycled plastic materials can only be placed in the market if they are free from contaminants at harmful levels. This work studies the thermal decontamination of poly(hydroxybutyrate-co-valerate) (PHBV) intended for food contact. PHBV was first contaminated with gallic acid, catechin, ferulic acid, and PEG 200, at 500 mg/kg. Thermal decontamination was then applied at 160(degrees)C for 6 and 48 h. Due to the low volatility of these molecules and their hydrogen bonding interactions with the polymer, decontamination efficiency was well below safety limits. Indeed, only 25.9% of gallic acid, 68.5% of catechin, 67% of ferulic acid, and 86.8% of PEG 200 were removed. In addition, a strong degradation of the polymer was observed (M-w decrease of 57%). To try to prevent polymer degradation, while enhancing decontamination conditions, quercetin (a natural polyphenol) was used as a stabilizer at 0.5 wt%. After 6 h of decontamination, hydrogen bonds, and pi-stacking interactions were formed between quercetin and the contaminants, reducing their removal (-8.5% for gallic acid, -57.4% for catechin, -18.7% for ferulic acid, and -31.9% for PEG200). After 48 h, strong PHBV degradation was observed (-83% M-w and -45% X-c), particularly in the presence of quercetin.