## 3 Results
### Barrier Properties of Paper Multilayers
As for the permeability of limonene, which is used as a standard to determine the aroma barrier, the paper presented a permeance of 2.23 \(\times\) 10\({}^{-9}\) kg/m\({}^{2}\).Pa-s, correspond  
\begin{table}
\begin{tabular}{l c c c c c c} \hline  & & \multicolumn{2}{c}{**Water Vapor**} & \multicolumn{2}{c}{**Limonene Vapor**} & \multicolumn{2}{c}{**Oxygen**} \\ \cline{3-6} \multicolumn{1}{c}{**Sample**} & \multicolumn{1}{c}{**Thickness (\(\mu\)m)**} & \multicolumn{1}{c}{**Premeance \(\times\)**} & \multicolumn{1}{c}{**Permeability**} & \multicolumn{1}{c}{**Premeance \(\times\)**} & \multicolumn{1}{c}{**Premeability**} & \multicolumn{1}{c}{**Premeance \(\times\)**} \\  & & **10\({}^{\text{th}}\) (kg/m\({}^{2}\).Pa-s)** & \(\times\) 10\({}^{\text{th}}\) (kg.m/m\({}^{2}\).Pa-s)** & \(\times\) 10\({}^{\text{th}}\) (kg.m/m\({}^{2}\).Pa-s) & \(\times\) 10\({}^{\text{th}}\) (kg.m/m\({}^{2}\).Pa-s) & (m\({}^{2 ing to a permeability value of 6.50 \(\times\) 10\({}^{-13}\) kg.m/m\({}^{2}\).Pa-s. Permeance of the PHBV film was 5.80 \(\times\) 10\({}^{-10}\) kg/m\({}^{2}\).Pa-s, resulting in a permeability to limonene vapor of 6.95 \(\times\) 10\({}^{-15}\) kg.m/m\({}^{2}\).Pa-s. This result indicates that the microbial copolyester was also much less permeable to aroma than paper. This result is relevant since limonene is known to be a good plasticizer for polyesters, such as PHAs and PET, and thus solubility plays a stronger role than diffusion in permeability. For example, it has been previously described that PHBV films of about 100 \(\upmu\)m were able to adsorb 12.7 wt.% of limonene [49]. One can also observe that the permeance to limonene vapor of the PET-based multilayer film, the so-called PET film, was 4.91 \(\times\) 10\({}^{-11}\) kg/m\({}^{2}\).Pa-s. This value is equivalent to a permeability of 4.97 \(\times\) 10\({}^{-15}\) kg.m/m\({}^{2}\).Pa-s, assuming a monolayer material. Limonene permeability values for 75-\(\upmu\)m PHB and PET films of 6.38 and 6.43 \(\times\) 10\({}^{-15}\) kg.m/m\({}^{2}\).Pa-s have been respectively reported [55], which are relatively similar to the reported herein. In relation to the multilayers, the permeance values of PHBV/paper/PHB and PET/paper/PET multilayers were 4.44 \(\times\) 10\({}^{-10}\) and 7.82 \(\times\) 10\({}^{-11}\) kg/m\({}^{2}\).Pa-s, respectively. Therefore, as it did with water vapor, the use of double coatings improved the aroma barrier of paper significantly (\(p\) < 0.05). Although the improvement achieved with the PET film was significantly higher (\(p\) < 0.05), one should consider that both polyesters resulted in a permeance reduction of nearly two orders of magnitude compared with uncoated paper, and the PHBV film thickness was lower. Regarding the oxygen barrier capacity, it was not possible to determine the oxygen permeance of the uncoated paper since it was above the detection limit (D.L.) of the equipment (OTR of 432.000 cm\({}^{3}\)/m\({}^{2}\). day). The PHBV film presented a permeance to oxygen of 2.41 \(\times\) 10\({}^{-14}\) m\({}^{3}\)/m\({}^{2}\).Pa-s. The oxygen permeance was previously determined for a 50-\(\upmu\)m film of the same PHBV grade, resulting in a value of 5.78 \(\times\) 10\({}^{-15}\) m\({}^{3}\)/m\({}^{2}\).Pa-s [56]. This permeance corresponds to an oxygen permeability of 2.9 \(\times\) 10\({}^{-19}\) m\({}^{3}\).m/m\({}^{2}\).Pa-s, which is nearly 50% higher than that of PHBV with 2 -3 mol% 3 HV; that is, 2.1 \(\times\) 10\({}^{-19}\) m\({}^{3}\).m/m\({}^{2}\).Pa-s [57]. The permeance to oxygen of the PET film was 8.10 \(\times\) 10\({}^{-16}\) m\({}^{3}\)/m\({}^{2}\).Pa-s. This corresponds to a permeability of 8.60 \(\times\) 10\({}^{-20}\) m\({}^{3}\).m/m\({}^{2}\).Pa-s and an OTR of approximately 7.2 cm\({}^{3}\)/m\({}^{2}\).day at 1 atm, assuming a monolayer material. Similar to WVTR, this value was also lower than the OTR values reported by the manufacturer, namely 14 and 20 cm\({}^{3}\)/m\({}^{2}\).day when measured at 0 and 90% RH, respectively, at 1 bar and 23\({}^{\circ}\)C (ASTM D3985).