*2.1. Materials*

PHBV copolyester was produced at a pilot-plant scale at the Universidade NOVA de Lisboa (Lisboa, Portugal). This biopolymer was obtained using mixed microbial cultures fed with fermented fruit waste derived from the manufacturing of fruit juice, supplied by SumolCompal S.A. (Lisbon, Portugal). The molar fraction of the 3-hydroxyvalerate (HV) in the copolyester used was 20%. The synthesis, purification, and characterization details of this biopolymer was thoroughly described in Reference [39].

Chloroform, reagen<sup>t</sup> grade with 99.8% purity, and methanol, HPLC grade with 99.9% purity, were purchased from Panreac S.A. (Barcelona, Spain). Additionally, 1-Butanol, reagen<sup>t</sup> grade with 99.5% purity, and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) were purchased from Sigma Aldrich S.A. (Madrid, Spain).

OEO had a purity >99% and a relative density of 0.925–0.955 g/mL. RE presented a relative density of 0.915–0.926 g/mL, an acidity index of ≤1 mg KOH/g, an iodine index of 80.0–145.0%, a saponification index of 180–200 mg KOH/g, and a peroxide index of ≤5.0 meqO2/kg. GTE showed a relative density of 0.915–0.925 g/mL, an acidity index of ≤1 mg KOH/g, an iodine index of 80–145%, a saponification index of 188–195 mg KOH/g, and a peroxide index of ≤5.0 meq O2/Kg. All natural products were obtained from Gran Velada S.L. (Zaragoza, Spain) and were processed as received.

#### *2.2. Preparation of the Solutions*

The PHBV solution was prepared by dissolving 10% (wt./vol.) of biopolymer in a chloroform/ 1-butanol 75:25 (vol./vol.) mixture, both reagen<sup>t</sup> grades, at room temperature. The OEO, RE, and GTE, were all added to the solution at 10 wt.% in relation to the PHBV and stirred for 24 h until a single-phase solution was obtained.

#### *2.3. Characterization of the Solution Properties*

All the PHBV solutions were analyzed in terms of their viscosity, surface tension, and conductivity. The apparent viscosity (ηa) was determined at 100 s<sup>−</sup><sup>1</sup> using a rotational viscosity meter Visco BasicPlus L from Fungilab S.A. (San Feliu de Llobregat, Spain). The surface tension was measured following the Wilhemy plate method using an EasyDyne K20 tensiometer from Krüss GmbH (Hamburg, Germany). The conductivity was evaluated using a conductivity meter HI9819X from Hanna Instruments

(Woonsocket, Rhode Island, USA). All the measurements were carried out at room temperature and in triplicate.
