Active food packaging involves the packaging of foods with materials that provide an enhanced functionality, such as antimicrobial, antioxidant or biocatalytic functions. This can be achieved through the incorporation of active compounds into the matrix of the commonly used packaging materials, or by the application of coatings with the corresponding functionality through surface modification. The latter option offers the advantage of preserving the packaging materials' bulk properties nearly intact. Herein, different coating technologies like embedding for controlled release, immobilization, layer-by-layer deposition, and photografting are explained and their potential application for active food packaging is explored and discussed.

Pectin was extracted from blueberry powder into three fractions of water soluble (WSF), chelator soluble (CSF) and sodium carbonate soluble (NSF). The fractions were incubated with cyanidin-3-glucoside (C3G), a mixture of five anthocyanidins (cyanidin, pelargonidin, malvidin, petunidin and delphinidin) or blueberry juice at pH 2.0-4.5. Free anthocyanins and bound anthocyanin-pectin mixtures were separated by ultrafiltration. WSF bound the least amount of anthocyanin at all pH values. CSF had stronger anthocyanin binding ability at pH 2.0-3.6, while NSF had stronger anthocyanin binding ability at pH 3.6-4.5. The pectin and anthocyanin binding was lowest at pH 4.5 and higher at pH 2.0-3.6. Nearly doubling C3G pigment content increased bound anthocyanin percentage by 16-23% at pH 3.6, which favored anthocyanin aromatic stacking, compared to 3-9% increase at pH 2.0. Ionic interaction between anthocyanin flavylium cations and free pectic carboxyl groups, and anthocyanin stacking may be two major mechanisms for pectin and anthocyanin binding.

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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.