Reactive extrusion of bio-derived active packaging offers a new approach to address converging concerns over environmental contamination and food waste. Herein, metal-chelating nitrilotriacetic acid (NTA) ligands were grafted onto poly­(lactic acid) (PLA) by reactive extrusion to produce metal-chelating PLA (PLA-g-NTA). Radical grafting was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy with the introduction of secondary alkyl stretches (2919 and 2860 cm–1) and by X-ray photoelectron spectroscopy (XPS) with an increase in the atomic percentage of nitrogen. Compared to films prepared from native, granular PLA (gPLA), PLA-g-NTA films had lower contact angles and hysteresis values (86.35° ± 2.49 and 31.89° ± 2.27 to 79.91° ± 1.58 and 21.79° ± 1.72, respectively), supporting the surface orientation of the NTA ligands. The PLA-g-NTA films exhibited a significant antioxidant character with a radical scavenging capacity of 0.675 ± 0.026 nmol Trolox(eq)/cm2 and an iron chelation capacity of 54.09 ± 9.36 nmol/cm2. PLA-g-NTA films delayed ascorbic acid degradation, retaining ∼45% ascorbic acid over the 9-day study compared to <20% for control PLA. This research makes significant advances in translating active packaging technologies to bio-derived materials using scalable, commercially translatable synthesis methods.

Concern over environmental contamination and the need for industrially produced functional biopolymers motivates the utilization of reactive extrusion for functional grafting. Antioxidant nonmigratory active materials were synthesized through 1,3-bis(4,5-dihydro-2-oxazolyl)benzene ring opening polymerization with bio-based poly(lactic acid) (PLA) and antioxidant nitrilotriacetic acid (NTA). Grafting was confirmed through the introduction of new alkyl stretching, disappearance of the characteristic 1,3-bis(4,5-dihydro-2-oxazolyl)benzene band, and emergence of new amide band on attenuated total reflectance Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy (XPS) showed stepwise increases in atomic nitrogen percentage and shifts in proportion of CC:CO bonding, confirming grafting and surface orientation. Antioxidant samples exhibited significant increases in carboxylate density, ranging from 0.75 ± 0.04 to 3.11 ± 0.04 nmol/cm 2. Functionalized films demonstrated significant antioxidant properties with Trolox (eq) ranging from 0.36 ± 0.02 to 0.89 ± 0.07 nmol/cm 2 according to radical scavenging studies and delayed greater than 52% of ascorbic acid degradation. This work develops a rapid functionalization method for biopolymers and displays efficacy in producing sustainable nonmigratory active materials.

Active packaging can enhance the performance of natural antimicrobials in controlling food spoilage and waste, while addressing consumer demands for cleaner labels. Yet, synergies are system dependent, with some conditions counterintuitively promoting antagonistic effects. In particular, metal chelators can improve performance of certain natural antimicrobials and have been incorporated in nonmigratory metal chelating active packaging technologies. However, the influence of chelating ligand chemistry on antimicrobial efficacy has not been investigated in microbial spoilage models. The effect of three commercial chelating resins on the growth of Alicyclobacillus acidoterrestris ATCC 49025, a thermoduric acidophilic spore‐former, in growth media and apple juice was investigated. Dowex MAC‐3, Chelex 100, and Lewatit TP260 were used as models for metal chelating active packaging containing carboxylic acid (CA), iminodiacetic acid (IDA), and aminomethylphosphonic acid (AMPA) ligands. Diameters (CA = 472.4 ± 117.2 μm, IDA = 132.93 ± 26.71 μm, and AMPA = 498.3 ± 29.24 μm), dissociation kinetics (CA = 6.44 ± 0.109, IDA = ‐0.977 ± 9.94, AMPA = 7.43 ± 0.193), and metal chelating capacities (CA = 1.16 × 10−4 mol/g, IDA = 1.52 × 10−3 mol/g, and AMPA = 4.67 × 10−4 mol/g) were used to distinguish differences in antimicrobial efficacies. Growth of A. acidoterrestris in acidified Potato Dextrose Broth over 24 hr with chelating resins indicated early death phase for CA and IDA resins and bactericidal for AMPA resin. However, viability in commercial apple juice with the inclusion of nisin and chelating resins was variable, with IDA resin significantly (P < 0.05) increasing viability while the effect of CA and AMPA resins remained elusive. This work emphasizes the importance of biological repeatability and correct statistical modeling in identifying conditions under which the antimicrobial intervention of nisin in real food systems, such as acidic beverages and juices, are synergistic or antagonistic. Practical Application New technologies to control microbial food spoilage and waste need to be explored to address consumers on‐going demands for reducing additive use.  Solid support bound metal chelators can both promote and control microbial growth when used in conjunction with nisin, a natural antimicrobial.  This work explores how system conditions can render a given technology either synergistic or antagonistic, and highlights the importance of sufficient biological replicates in experimental design.

Active packaging offers a unique approach to improving food quality and safety; yet, there remains a need for translatable production methods. We report synthesis of nonmigratory, antimicrobial active packaging. Polylysine (PL) was grafted onto polypropylene (PP) using a free-radical initiator via reactive extrusion, yielding PP-g-PL. PP-g-PL retained similar hydrophobicity to native PP (native PP 109.2 ± 5.6°; PP-g-PL5 116.1 ± 4.8°), important for desirable product-release properties. The surface orientation of polylysine was monitored by the presence of amine groups, with negligible (1.0 ± 0.3 nmol/cm2) amines on control PP and 4.7 ± 1.3, 7.4 ± 2.2, and 10.6 ± 3.8 nmol/cm2 amines on PP-g-PL prepared with 1%, 2%, and 3% polylysine. The antimicrobial active packaging material enabled a 1-log reduction in P. aeruginosa after 1 h incubation at 37 °C. These results suggest that nonmigratory active packaging can be prepared by reactive extrusion, a scalable technology, with promise in improving food safety and reducing food waste.

No abstract