Synthesis of Iminodiacetate Functionalized Polypropylene Films and Their Efficacy as Antioxidant Active-Packaging Materials

Abstract

The introduction of metal-chelating ligands to the food-contact surface of packaging materials may enable the removal of synthetic chelators (e.g., ethylenediamine tetra-acetic acid (EDTA)) from food products. In this study, the metal-chelating ligand iminodiacetate (IDA) was covalently grafted onto polypropylene surfaces to produce metal-chelating active-packaging films. The resulting films were able to chelate 138.1 ± 26 and 210.0 ± 28 nmol/cm(2) Fe(3+) and Cu(2+) ions, respectively, under acidic conditions (pH 3.0). The films demonstrated potent antioxidant efficacy in two model food systems. In an emulsified-oil system, the chelating materials extended the lag phase of both lipid hydroperoxide and hexanal formation from 5 to 25 days and were as effective as EDTA. The degradation half-life of ascorbic acid in an aqueous solution was extended from 5 to 14 days. This work demonstrates the potential application of surface-grafted chelating IDA ligands as effective antioxidant active food-packaging materials.

The Role of Solid Support Bound Metal Chelators on System‐Dependent Synergy and Antagonism with Nisin

“…Similar to carboxylic acid resin, shifts were observed indicating the deprotonation of the carboxylic acid group on the iminodiacetic acid ligand (Figure B). This value is lower than the published literature value for free iminodiacetic acid of 1.82 and 2.61 for carboxylate groups as well as the pKa bulk value of 4.85 for the iminodiacetic acid bound to polypropylene (Lin et al., ). These results may be due to the calculated value being outside of experimental conditions as well as differences in dissociation behavior when bound to styrene divinylbenzene compared to polypropylene, for which pKa values are reported.…”

“…While the pKa value of the carboxylic acid groups on the iminodiacetic acid resin was determined to be below 0, indicating complete dissociation and full chelating capacity at pH 4.0, it has been reported that the overall pKa (pKa bulk ) of iminodiacetic acid groups is 4.85, suggesting incomplete dissociation at pH 4.0, similar to that of the carboxylic acid. As a result, neither carboxylate based chelating resin influenced exponential growth of A. acidoterrestris ATCC 49025, suggesting that in the presence of these weak chelating agents, it is able to acquire transition metals despite being bound by carboxylate chelators (Lin et al., ). Indeed, in iron poor environments, many bacteria produce high affinity, low molecular weight chelating compounds termed siderophores with stability constants greater than 45 (Miethke & Marahiel, ; Neilands, ; Zhang et al., ).…”

Photo‐Curable Metal‐Chelating Coatings Offer a Scalable Approach to Production of Antioxidant Active Packaging

“…IDA functionalized materials are expected to have the same amino‐dicarboxylic acid ligands as EDTA, permitting similar metal‐chelating performance as EDTA in food systems. In a recent study, IDA functionalized materials showed equivalent antioxidant efficacy as EDTA against lipid oxidation in emulsified oil systems in neutral to high acid conditions (Lin et al., ). In comparison, metal‐chelating materials with less specific chelating ligands (for example, carboxylic acid) lost antioxidant efficacy in high acid conditions (Tian, Decker, McClements, & Goddard, ).…”

“…Such batch chemical reactions have been reported for preparation of a range of metal‐chelating materials, such as nanoparticles (Goon, Zhang, Lim, Gooding, & Amal, ), resins (Atzei, Ferri, Sadun, Sangiorgio, & Caminiti, ; El‐Nahhal et al., ), membranes (Yamada, Nagano, & Hirata, ; Zhu, & Sun, ), and fabrics (Kavaklı, Kavaklı, & Güven, ). In our previous studies, metal‐chelating active packaging materials were also fabricated via batch reactions in ligand solutions to tether metal‐chelating ligands (Lin et al., ; Lin, Decker, and Goddard, ; Roman, Decker, & Goddard, ). For example, the IDA functionalized materials were prepared via a 10‐h chemical reaction in a concentrated IDA solution to tether IDA ligands to reactive surfaces bearing chlorine groups (Lin et al., ).…”

“…In our previous studies, metal‐chelating active packaging materials were also fabricated via batch reactions in ligand solutions to tether metal‐chelating ligands (Lin et al., ; Lin, Decker, and Goddard, ; Roman, Decker, & Goddard, ). For example, the IDA functionalized materials were prepared via a 10‐h chemical reaction in a concentrated IDA solution to tether IDA ligands to reactive surfaces bearing chlorine groups (Lin et al., ). Therefore, despite the promising laboratory results of metal‐chelating active packaging technologies, the industrial translatability of the technology remains limited.…”