Development of controlled-release antioxidant poly (lactic acid) bilayer active film with different distributions of α-tocopherol and its application in corn oil preservation.

The antioxidant poly (lactic acid) bilayer active films with a different distribution of α-tocopherol (TOC) in two layers (outer layer/inner layer: 0%/6%, 2%/4%, 3%/3%, 4%/2%, 6%/0%) were developed. The effects of TOC distribution on the structural, physicochemical, mechanical, antioxidant and release properties of the films and their application in corn oil packaging were investigated. The different distributions of TOC showed insignificant effects on the color, transparency, tensile strength and oxygen and water vapor barrier properties of the films, but it affected the release behavior of TOC from the films into 95% ethanol and the oxidation degree of corn oil. The film with higher TOC in outer layer showed a slower release rate. The corn oil packaged by the film containing 4% TOC in outer layer and 2% TOC in inner layer exhibited the best oxidative stability. This concept showed a great potential to develop controlled-release active films for food packaging.

Development of New Multilayer Active Packaging Films with Controlled Release Property Based on Polypropylene/Poly(Vinyl Alcohol)/Polypropylene Incorporated with Tea Polyphenols.

The polypropylene/poly(vinyl alcohol)/polypropylene (PP/PVA/PP) multilayer active films with controlled release property were developed, of which the intermediate PVA layer was incorporated with 4% (w/w) tea polyphenols (TP) and the microporous PP films with different pore size were used as the internal controlled release layer. The SEM results showed that each layer of these films was agglutinated tightly. With increasing pore size from 171.05 to 684.03 µm, there were little effect on the films' color and opacity, the tensile strength (TS) and elongation at break (EAB) decreased slightly, the gas barrier (O2 and water vapor) property of the film reduced faintly, the time of achieving the release equilibrium in 50% ethanol decreased from 75 hours to 30 hours. The diffusion coefficient for the films increased with the increase of pore size, from 2.06 × 10-11 cm2 /s to 8.06 × 10-11 cm2 /s, suggesting that the release rate of TP increased as the pore size increased. The results were indicated that its release rate could be controlled by adjusting the size of pore. The films also exhibited different antioxidant activities due to their different release profiles of TP. It showed promise for developing the controlled release active packaging film based on this concept. PRACTICAL APPLICATION: Controlled release packaging is propitious to extension of food shelf life. The microporous polypropylene films with different pore size used as the internal layer of polypropylene/poly(vinyl alcohol)/polypropylene (PP/PVA/PP) multilayer active films was proved that the release rate of tea polyphenols in the intermediate PVA layer released from the films into the food simulant can be controlled by adjusting the size of pore in this study. It showed a good prospect for using microporous or perforation-mediated film as the internal layer of multilayer film to develop the controlled release active packaging film for food packaging.