Submitted to: Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2016
Publication Date: 9/6/2016
Citation: Yang, W., Sousa, A.M., Thomas-Gahring, A.E., Fan, X., Jin, Z.T., Li, X., Tomasula, P.M., Liu, L.S. 2016. Electrospun polymer nanofibers reinforced by tannic acid/Fe+++ complexes. Materials. 9(757):1-12. doi: 10.3390/ma9090757.

Interpretive Summary: Tannic acid (TA) can be extracted from coffee, tea, and other food products. TA exhibits antioxidant and antibacterial properties, and has been tested for food preservation applications. To mask the presence of TA residues in food products that may impact on their appearance and taste, TA has been enclosed in formulations such as films, membranes or capsules prior to using as an antioxidant. However, the efficiency of TA was limited by the small surface areas of these methods. In this research, TA was formed into stable complexes with ferric ion (an Iron compound) and loaded into PVA nanofibers by electrospinning, a process that makes the nanofibers. Because the nanofibers have a large surface area and can hold a large amount of TA, the fibers showed antioxidant activity as strong as non-enclosed TA when tested to suppress sunflower oil oxidation. Also, the fibers were easy to remove from the oil at the end of use. This method has potential applications in oils and fats preservation.

Technical Abstract: Nanofibers and fibrous mats of polyvinyl alcohol (PVA) loaded with tannic acid (TA) and ferric ion (Fe+++) complexes (TA-Fe+++) were synthesized by the electrospinning technique. The spinning solutions were characterized for surface tension, electrical conductivity, and viscosity. It was found that PVA, as the main component, dominated the solution properties, although changes in solution pH resulted in structural changes of the TA-Fe+++ complexes from one ferric ion coupling with a single galloyl group of TA [mono-complex TA/Fe+++ (I)] to coupling with multi galloyl groups [bi-complex TA-Fe+++ (II)] and [tri-complex TA-Fe+++ (III)]. The morphology of the complex fibers thus obtained, as well as their size and size distribution were dependent on the PVA content and the pH of the spinning solutions, as found by scanning electron microscopy. The complex of TA with ferric ions did not alter the oxidation activity of TA as confirmed by the conjugated diene formation assay in sunflower oil. However, complexation of TA with Fe+++ enhanced the mechanical properties of the PVA/TA-Fe+++ nanofibers and fibrous mats. The PVA nanofibers and fibrous mats encapsulated with TA-Fe+++ showed potential applications in oils and fats preservation.