2.3.9. D-Limonene Permeability

Permeability to limonene vapor was measured as described above for WVP. For this, 5 mL of D-limonene was placed inside the Payne permeability cups. The cups containing the films were placed at controlled environmental conditions, i.e., 23 ◦C and 40% RH. Limonene vapor permeation rates were estimated from the steady-state permeation slopes and the weight loss was calculated as the total cell loss minus the loss through the sealing. The samples were measured in triplicate and the limonene permeability (LP) values were calculated taking into account the average film thickness in each case.

#### 2.3.10. Oxygen Scavenging Activity

Round-bottom Schlenk flasks from VidraFoc S.A. (Barcelona, Spain) with a PTFE stopcock and a headspace volume of 50 cm<sup>3</sup> were used for the oxygen scavenging measurements. The flasks contained a valve for gas flushing in and a O2-sensitive sensor spot (PSt3, detection limit 15 ppb, 0–100% oxygen) from PreSens (Regensburg, Germany) was glued onto the inner side of the flasks for measuring oxygen depletion. The electrospun fibers and films were cut (5 × 5 cm2) and placed into the flasks. The flask was subsequently flushed for 30 s at 1 bar with a gas mixture containing 1 vol. % oxygen, 4 vol. % hydrogen, and 95 vol. % nitrogen, which was provided by Abelló Linde, S.A. (Barcelona, Spain). The oxygen concentration in the cell was monitored by a non-destructive measurement method using the OXY-4 mini (PreSens) multi-channel fiber optic oxygen meter for simultaneous read-out of up to 4 oxygen sensors, used with sensors based on a 2 mm optical fiber. Oxygen concentrations over time were measured by linking the light-emitting (600–660 nm) optical fibers to the flasks inner sensing spots. The sensor emits a certain amount of luminescence depending on the oxygen concentration in the cell that was calibrated to yield concentration by the equipment. All measurements were carried out at 23 ◦C and at 50% and 100% RH.
