Electrospinning Machine | Schiff base crosslinking based dialdehyde-chitosan/gelatin/tea polyphenol electrospun nanofibrous membranes with excellent antibacterial and antioxidant activity for food packaging

Currently, developing novel food packaging using electrospinning technology is a popular research direction. The spinning materials involved are mainly synthetic polymers (PCL, PLA, PVA, etc.), which have slow degradation rates and certain environmental impacts, not conducive to the current concept of green and sustainable development. In contrast, many natural products (such as gelatin, zein, chitosan, etc.) have faster biodegradation rates and are environmentally friendly, and they even possess certain functional properties themselves, making them applicable for developing novel food packaging. However, in practical applications, preparing membrane materials with good water stability, tensile resistance, and antibacterial and antioxidant properties that can adapt to the actual food packaging environment is a significant challenge.

Recently, Professor Li Yongxin and Professor Huang Hui's team from Jilin University published their latest research findings titled "Schiff base crosslinking based dialdehyde-chitosan/gelatin/tea polyphenol electrospun nanofibrous membranes with excellent antibacterial and antioxidant activity for food packaging" in the journal Food Packaging and Shelf Life. The researchers prepared dialdehyde-chitosan (DCS)/gelatin (GEL)/tea polyphenol (TP) nanofibrous membranes (DCS/GEL/TP-M) with excellent water stability, antibacterial, and antioxidant activity through polysaccharide modification, electrospinning process, Schiff base crosslinking, and thermal crosslinking technology.

Figure 1: Fabrication and morphology of DCS/GEL/TP-M nanofibrous membranes.

Scanning electron microscope images and corresponding membrane diameter distribution showed smooth, continuous, bead-free fibrous morphology for all groups, indicating good compatibility among DCS, GEL, and TP. According to size analysis, the fiber diameter of the membranes was found to be in the range of 200-400 nm. When the TP content increased from 5% to 20%, the average fiber diameter gradually decreased from 325 nm to 220 nm. Meanwhile, characterization methods such as infrared spectroscopy and XRD further demonstrated the successful oxidation of chitosan to dialdehyde chitosan and the loading of tea polyphenols on the membrane. The release process of tea polyphenols from the membrane in vitro was tested, and fitting of the release results indicated that the release behavior of tea polyphenols from the membrane in vitro belongs to Fickian diffusion. The thermal stability, water stability, mechanical strength, and other properties of the membrane DCS/GEL/TP-M were also tested. It was found that the Schiff base crosslinking and thermal crosslinking processes improved the material's properties to some extent, especially water stability. Before thermal crosslinking, the membrane collapsed in water. After thermal crosslinking, the weight loss rate of the membrane could be as low as 17.25±2.51 (%).

Figure 2: Scanning electron microscopy images and diameter distribution of DCS/GEL/TP-M: (A,a) MDGT5; (B,b) MDGT10; (C,c) MDGT15; (D,d) MDGT20.

Figure 3: Characterization of DCS/GEL/TP-M: (A, B) FTIR spectra; (C) XRD; (D) TGA curve; (E) Mechanical strength; (F) Release performance.

Figure 4: (A) Growth of S. aureus and E. coli after treatment with different membranes; (B) Inhibition rate of different membranes against S. aureus; (C) Inhibition rate of different membranes against E. coli; (D) DPPH free radical scavenging ability of different membranes.

Figure 4 reflects the prepared membrane's good antibacterial and antioxidant properties. The incorporation of TP enhanced the membrane's antibacterial ability, and as the TP content in the membrane increased, the antibacterial effect became more significant. The inhibition rates of membrane MDGT20 against E. coli and S. aureus were 91.08% and 89.31%, respectively. This is because TP, as an excellent antibacterial substance, can bind to the bacterial cell membrane, change its permeability, cause leakage of internal bacterial substances, leading to bacterial death. Similarly, the incorporation of TP also greatly improved the membrane's antioxidant capacity (Figure 4D). Without incorporation, the DPPH free radical scavenging rate of membrane MDGT0 was only 23.67±3.66%. After adding 5% TP, the DPPH free radical scavenging rate reached 68.07±2.47%, indicating a significant improvement in the membrane's antioxidant performance. Within a certain range, the amount of TP incorporated in the membrane was positively correlated with the membrane's antioxidant performance. Membrane MDGT20 had the highest DPPH free radical scavenging rate at 85.42±2.61%. Overall, the membrane has good antibacterial and antioxidant properties, which can, to some extent, inhibit microbial activity and slow down the food's own oxidation process during preservation.

Figure 5: (A) Actual situation of strawberries wrapped with different membranes and stored at 25°C for 7 days; (B) Changes in weight loss rate of strawberries; (C) Changes in hardness of strawberries; (D) Changes in DPPH free radical scavenging rate of strawberry fruits; (E) Changes in total phenolic content of strawberry fruits; (F) Changes in catalase activity in strawberry fruits; (G) Changes in malondialdehyde content in strawberry fruits.

Furthermore, the prepared membrane was used for actual packaging tests on strawberries, and the test results are shown in Figure 5. It can be observed that the freshness of the test group strawberries (strawberries coated with DCS/GEL/TP-M membrane) was higher than that of the control group and PE group (Figure 5A). In terms of test indicators, the weight loss rate and hardness change of the test group strawberries were smaller than those of the control and PE groups. The total phenolic content (TPC), catalase activity (CAT), and DPPH free radical scavenging rate of the test group strawberries maintained relatively high levels compared to the control and PE group strawberries. Meanwhile, the malondialdehyde content in the test group strawberries was relatively low, indicating a lower degree of peroxidation in the test group strawberries. This suggests that the DCS/GEL/TP-M membrane can effectively delay the oxidation of strawberries. According to the total colony count of strawberries in each group on day 1 and day 7, the test group strawberries had fewer total colonies than the control and PE groups, with the MDGT20 group having the least total colonies. This indicates that the prepared DCS/GEL/TP-M membrane can effectively inhibit bacterial growth in the fruit to some extent.

Paper link: https://doi.org/10.1016/j.fpsl.2025.101568