Migration of α-tocopherol and resveratrol from poly(L-lactic acid)/starch blends films into ethanol

Poly(L-lactic acid) (PLLA)/starch blends with various concentrations of two natural antioxidants, α-tocopherol (α-TOC) and resveratrol, were fabricated by a melt blending and compression molding processes. The effects of the two antioxidants on the optical (color), thermal and mechanical properties of PLLA/starch blends with antioxidants were assessed. PLLA/starch blend films with α-TOC and resveratrol showed a yellowish color influenced by the combined effect of white starch and the brown color of the antioxidants. The glass transition and melting temperatures were significantly reduced with the addition of antioxidants while enhanced thermal stability was observed, which could be a benefit and important for processing and production. The enhanced mechanical properties could be attributed to not only a compatibilization effect based on the chemical linkage between PLLA and starch chains, but also restriction of the chain mobility by antioxidants. The release of resveratrol from PLLA and PLLA/starch blend films into ethanol followed Fickian behavior. The D values of α-TOC were in the range of 0.47–3.95 × 10−11 cm2 s−1 for PLLA films and 0.70–6.83 × 10−11 cm2 s−1 for PLLA/starch blend films at 13 °C, 5.67–13.0 × 10−11 cm2 s−1 for PLLA films and 4.10–24.2 × 10−11 cm2 s−1 for PLLA/starch blend films at 23 °C, and 89.0–118.0 × 10−11 cm2 s−1 for PLLA films and 123–282 × 10−11 cm2 s−1 for PLLA/starch blend films at 43 °C. The D values of resveratrol were in the range of 0.073–0.54 × 10−10 cm2 s−1 for PLLA films and 1.42–6.93 × 10−10 cm2 s−1 for PLLA/starch blend films at 13 °C, 0.90–3.44 × 10−10 cm2 s−1 for PLLA films and 4.16–22.3 × 10−10 cm2 s−1 for PLLA/starch blend films at 23 °C, and 24.8–74.1 × 10−10 cm2 s−1 for PLLA films and 40.1–309 × 10−10 cm2 s−1 for PLLA/starch blend films at 43 °C.

► Poly(L-lactic acid)/starch blends with α-tocopherol and resveratrol were produced. ► The addition of the two antioxidants enhanced the mechanical properties of the blends. ► The release of α-tocopherol and resveratrol from PLLA/starch and PLLA films into ethanol was modeled. ► Dual antioxidants release from PLLA/starch blends increased when compared with PLLA films. ► PLLA/starch blend allows more efficient release of the two antioxidants.