Release property and antioxidant effectiveness of tocopherol-incorporated LDPE/PP blend films

Abstract

Low-density polyethylene (LDPE)/polypropylene (PP) blend films in various blending ratios containing 3000 mg kg⁻¹ of tocopherol were manufactured by an extrusion process. Tocopherol release properties were characterised and correlated with antioxidant effectiveness in retarding the oxidation of linoleic acid contacting the films at 40°C. The conditions without tocopherol (control) and with instant tocopherol addition corresponding to the amount included in the films were also prepared and compared with the film-contacting solutions. The effect of tocopherol inclusion and the blending ratio on their physical properties was also examined. A wide range of tocopherol diffusivity in 6.6 × 10⁻¹⁶-4.6 × 10⁻¹⁴m² s⁻¹ were obtained by blend films. As PP content increases, the diffusivity decreased sharply at the beginning and levelled off later. The slower release of tocopherol in LDPE/PP blend films corresponding to lower tocopherol diffusivity retained the higher tocopherol concentration in the linoleic acid system providing better antioxidant effectiveness of the extended induction period in oxidation. The tocopherol inclusion reduced tensile strength and transparency significantly in an affordable range with higher tensile strength given by a higher PP ratio. LDPE/PP blending can be a useful tool to modulate the release profile of tocopherol and thus the antioxidant effectiveness of the tocopherol-incorporated antioxidant packaging film.

Release Kinetics of Tocopherol and Quercetin from Binary Antioxidant Controlled-Release Packaging Films

“…The polymer blending ratio has been reported to significantly affect the release of tocopherol from LDPE/PP blend films. 4 Release of Tocopherol and Quercetin from Binary Antioxidant CRP Films. Figure 3 shows that tocopherol (first and second curves) released more quickly but for a shorter period of time than quercetin (third and fourth curves) in LDPE and EVOH films.…”

Preparation of antioxidant active films based on chitosan: diffusivity study of α-tocopherol into food simulants

“…Siró et al (2006) reported a diffusion coefficient of 1.68 9 10 -12 cm 2 /s for a-tocopherol forming complexes with beta-cyclodextrin from LDPE polymer into 95 % EtOH (v/v) at 7°C, and a value of D one order of magnitude lower (1.53 9 10 -11 cm 2 /s) for the non-complexed form. D values ranging from 6.58 9 10 -12 to 4.60 9 10 -10 cm 2 /s were obtained for a LDPE/ polypropylene (PP) blend films-95 % EtOH (v/v) system (Zhu et al 2012). Castro López et al (2012 evaluated the release of a-tocopherol from polypropylene (PP) film modified with poly(propyleneglycol)-block-poly(ethylene glycol)-block-poly(propyleneglycol) (PPG-PEG-PPG) into the food simulant 50 % EtOH (v/v) at 40°C and reported values were between 2.4 9 10 -12 and 2.0 9 10 -11 cm 2 /s.…”

“…Nevertheless, this approach presents some drawbacks such as that large amounts of the antioxidants are needed, in some cases there are established maximum permitted levels by food legislation, and moreover at high concentrations they can act as pro-oxidants (Gargiulo et al 2013). In past years the antioxidant active packaging appeared as an innovative technology that may supply a sustained delivery of the active compound, maintaining an effective concentration over the time (Zhu et al 2012). In these systems the antioxidant is incorporated into the polymeric matrix intended to be in contact with the food product (Zhu et al 2013;Heirlings et al 2004;Siró et al 2006).…”

Antioxidative Packaging System

“…The release profile of tocopherol from packaging polymer to fatty liquid foods is governed by its diffusion in the polymer, where diffusivity is an important independent variable. For a given film thickness and tocopherol loading, the diffusivity of tocopherol depends on the blending ratio of the polymer, which was found to be an important variable in controlling the induction period of linoleic acid systems (Zhu et al, 2012a). An example analysis using the diffusion model has been reported by Lee and Yam (2013) and is presented in Figure 6.4.…”