Electrospun nonwovens composed of submicrom fibers are gaining popularity in filtration, coatings, encapsulation and packaging applications. Their production with food-grade biopolymers and the inclusion of bioactive compounds within the fibers ensure their compatibility with food products and increase their functionality and sustainability. However, their potential uses are hindered by their limited stability, particularly when loaded with lipids.<br/>The objective of this study was to apply a multi-length scale approach to gain insights into the deteriorative processes that limit the shelflife of these novel materials.<br/>A zein solution (20% w/w) prepared in 7:3 propanol:water solution was added with corn oil (3:10 oil:protein ratio). The solution was electrospun through a neddle spinneret (0.7 mm diameter orifice) for 10min. Electrospun samples were stored under controlled conditions (dark, 23°C & 33 %RH) for 28 days and tested at selected intervals. Fiber morphology and nonwoven mechanical properties were assessed by scanning electron microscopy (SEM) and tensile tests, respectively. The overall lipid oxidation in the samples was assessed using a TBARS assay. The protein secondary structure was probed using Fourier Transform Infrared Spectroscopy (FTIRS) and the lipid distribution was assessed by microspectroscopic techniques (Raman & luminescence). The photophysical properties of intrinsic (Tyr) and extrinsic (BODIPY C11) lumiphores were also monitored during storage to assess changes in local molecular rigidity and lipid oxidation.<br/>SEM revealed ribbon-like fibers whose diameter significantly decreased during storage (700 ± 9 nm vs. 620 ± 10 nm). Extensive breakage of the fibers correlated with increased brittleness of the material, as reported from bulk and local measurements, e.g., decreased extensibility by 30% and increased Tyr emission intensity by 40%. Changes in mechanical properties and matrix rigidity also correlated with a transition in zein secondary structures from unordered (25% vs. 0%) to ordered structures (2% vs. 19%) during storage. Raman micrographs showed oil migration to the ribbon’s outer regions during storage, increasing lipid oxidation. The correlation between local rigidity and lipid oxidation suggests the potential interactions between the oxidation products and zein. Understanding the causes of deterioration can aid in developing smart strategies to improve the stability of these novel food-grade materials.

Material degradation inside and out: Contributions to the deterioration of electrospun matrices with encapsulated corn oil

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.