Release of synthetic phenolic antioxidants from extruded poly lactic acid (PLA) film

Abstract

Antioxidant-active packaging is a promising technology for food protection. In this study Poly lactic acid (PLA) granules containing 2% (w/w) synthetic phenolic antioxidants (SPA) including butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), and tert-butylhydroquinone (TBHQ) were extruded in a pilot plant extruder. SPA's release from PLA-SPA films into 10%, 50% and 95% ethanol at 20 °C and 40 °C was regularly measured by HPLC system for 60 days. TBHQ partially decomposed to 2-tert-butyl-1,4-benzoquinone (TBBQ) both during extrusion process and release tests under all conditions. Diffusion of the SPAs from PLA to simulants showed a Fick's behavior with diffusion coefficient (D) value between 10−8 and 10−11 cm2 s−1 with 0–100% of release. Faster and higher release of SPAs occurred at 40 °C according to Arrhenius law. PG and BHT had respectively the highest and lowest release rate in all simulants due to their different molecular properties such as polarity, Log P and molecular volume. Higher ethanol content of simulant and temperature both influenced the PLA hydrolysis during release study; at 40 °C, all PLA films in contact with 50% ethanol turned opaque and fragile. Total and fast release of SPA into 95% ethanol at 40 °C and their small release into 10% ethanol at 40 °C and 20 °C suggests using PLA-SPA active packaging for oils, oily foods and some milk products which are highly sensitive to oxidation to ensure higher food quality. Finally, PLA-antioxidant active packaging approach also permits to reduce the amounts of directly added antioxidants in foods to provide safer foods.