PHBV-based polymers as food packaging: Physical-chemical and structural stability under reuse conditions

Abstract

Until recently, reuse models for food packaging plastics were generally considered burdensome. Today, reuse is placed second in the waste management hierarchy of the plastics circular economy. This work addresses, for the first time, the reuse of biobased and biodegradable materials such as PHBV and PHBV-quercetin. The safety and structural integrity of the materials were evaluated in two scenarios: (i) within a full reuse cycle including: food contact/detergentwashing/food contact; and (ii) successive washing operations in water, detergent and NaOH aqueous solutions. PHBV material that underwent the full reuse cycle using aqueous (10% ethanol) and acidic (3% acetic acid) food simulants showed an overall migration close to zero with a maintenance of its physical-chemical properties. It was also able to withstand up to 20 cycles of washing in water and detergent with slight changes in its intrinsic properties. Its washing with a 1 wt% aqueous NaOH solution, for one cycle, led to the removal of its external surface without altering its physical-chemical properties. The use of quercetin as additive had no consequence in the first scenario (the full reuse cycle). Even the migration of a part of it (2 wt% from the initial amount in the polymer) in the first contact with the food was far below the admissible daily intake. However, the release of quercetin during detergent washing steps and the production of acidic oxidation products during NaOH washing contributed to accelerate material degradation, questioning the use of such additives for PHAs.