Large-Scale Nanofiber Manufacturing| Influence of debranched maize starch onpullulan/gelatin nanofibers loaded withdebranched starch-tannin complexes

South China University of Technology's Professor Gao Qunyu & University of Auckland's Paul Kilmartin: Influence of Debranched Corn Starch on the Properties of Electrospun Starch-Tannin Complexes

Grape seeds (Grape Seed), a byproduct of winemaking, are rich in tannins (Tannin), which are structurally diverse natural polyphenols with significant antioxidant and antimicrobial properties. However, their practical application often faces challenges such as activity degradation caused by light, heat, and humidity. Effectively protecting and releasing their active components has become crucial. In the food industry, efficiently utilizing food processing byproducts to enhance their added value is both challenging and meaningful.  Recently, a study successfully combined grape seed tannins with enzymatically modified corn starch to create antioxidant nanofiber membranes for food packaging using electrospinning technology, offering a new approach to "green packaging." 

 Recently, A collaborative study by Professor Gao Qunyu's team at South China University of Technology and Paul Kilmartin's team at the University of Auckland was published in *Carbohydrate Polymers* under the title *"Influence of debranched maize starch on pullulan/gelatin nanofibers loaded with debranched starch-tannin complexes."*  

To improve the utilization of tannin byproducts, the researchers introduced three types of corn starch with different amylose contents (high-amylose corn starch, normal corn starch, and waxy corn starch). Through enzymatic debranching (Debranching), amylose with varying chain-length distributions was obtained and further complexed with grape seed tannins to form different crystalline structures.  Subsequently, these starch-tannin complexes were combined with natural polymers pullulan (Pullulan) and gelatin (Gelatin) to prepare antioxidant nanofiber composite membranes using electrospinning (Electrospinning) technology. The researchers further investigated the influence of amylose chain-length distribution on the properties of electrospun starch-tannin complexes.  

Figure 1: Preparation and physicochemical properties of debranched starch-tannin complexes.  

As shown in Figure 1, after debranching:  

- Debranched waxy corn starch (DB-WMS) primarily consisted of short-chain amylose.  

- Debranched normal corn starch (DB-NMS) and debranched high-amylose corn starch (DB-HMS) primarily consisted of long-chain amylose.  

The resulting debranched starch-tannin complexes formed aggregates with loose surfaces and irregular lamellar structures. XRD analysis showed no crystalline peaks of tannins but revealed new crystalline structures, indicating non-physical mixing. The debranched high-amylose corn starch-tannin complex (DBH-T) and debranched normal corn starch-tannin complex (DBN-T) exhibited V+B-type crystalline structures, while the debranched waxy corn starch-tannin complex (DBW-T) showed weaker B-type crystalline structures with diffraction peaks at 2θ = 17°, 20°, and 22°.  The absorption peak near 1652 cm⁻¹, corresponding to the O-H bending vibration of adsorbed water, shifted or disappeared, indicating that tannins affected intermolecular and intramolecular hydrogen bonds in starch. Characteristic peaks at 1452 cm⁻¹, 1522 cm⁻¹, 1617 cm⁻¹, and 1285 cm⁻¹ in the FTIR spectra of the complexes were attributed to tannin peak shifts, confirming the formation of starch-tannin complexes.  

Figure 2: Morphology, physicochemical properties, and simulated release kinetics of fiber membranes.

As shown in Figure 2, DBH, DBN, and DBW all formed continuous, bead-free nanofibers with diameters exceeding 200 nm when combined with pullulan/gelatin. After loading with debranched starch-tannin complexes, the diameters of the composite nanofibers increased compared to those without tannins, indicating successful tannin encapsulation.  

The tannin loading efficiency of the composite fiber membranes was related to the formation of amylose-tannin complexes. Long-chain amylose-tannin complexes formed more stable V+B-type crystals compared to short-chain amylose-tannin complexes, improving the tannin loading efficiency. The tannin loading rates for waxy corn starch-tannin nanofibers (WPG-T), normal corn starch-tannin nanofibers (NPG-T), and high-amylose corn starch-tannin nanofibers (HPG-T) were 1.73 ± 0.09%, 2.64 ± 0.03%, and 2.54 ± 0.06%, respectively, endowing the fiber membranes with better antioxidant activity and mechanical properties.  XRD analysis of nanofibers containing debranched starch-tannin complexes showed broad amorphous peaks at 2θ = 10°–25°, and no characteristic tannin peaks were observed in the FTIR spectra of the composite nanofiber membranes after loading, indicating complete encapsulation of debranched starch within the pullulan/gelatin fibers. Additionally, the interaction between long-chain amylose and tannins was stronger than that between short-chain amylose and tannins, enhancing the mechanical properties and rigidity of the composite fiber membranes.  

In antioxidant activity tests, the DPPH radical scavenging rates of WPG-T NF were significantly lower than those of NPG-T NF and HPG-T NF (*P* < 0.05). Over 35 hours of release testing, NPG-T NF and HPG-T NF exhibited slightly slower tannin release rates than WPG-T NF, attributed to the more stable V-type crystalline structure formed by long-chain amylose-tannin complexes.  This study provides insights into the high-value utilization of winemaking byproducts.  

Paper link: [https://doi.org/10.1016/j.carbpol.2025.123630](https://doi.org/10.1016/j.carbpol.2025.123630)