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In this study, we prepared gelatin and chitosan as wall materials, and composites with a controlled release capability in a weak acidic environment were synthesized for loading and protecting anthocyanins. Fourier-transform infrared spectroscopy and scanning electron microscopy were used to assess the properties of the nanoparticles. The loading efficiencies and oxidation resistances of the proposed substances were measured. Under optimal conditions, the anthocyanins exhibited a loading efficiency of 83.81 %, and suitable long-term storage capacity at room temperature with a retention rate of ∼50 % after 15 d. When the nanoparticles were used for detecting the milk freshness, spoiled milk exhibited a reddish color, whereas the color of fresh milk did not change. Moreover, these nanoparticles exhibited a stable chroma in milk for 0-16 h. Therefore, the proposed pH responsive nanoparticles can provide a possibility for the dynamic monitoring of milk quality changes, or provide some reference value for future related research., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Response Surface Methodology (RSM) was used to assess the optimal conditions for a Water/Oil/Water (W/O/W) emulsion for encapsulated nisin (EN). Nano-encapsulated nisin had high encapsulation efficiencies (EE) (86.66 ± 1.59%), small particle size (320 ± 20 nm), and low polydispersity index (0.27). Biodegradable polyvinyl alcohol (PVA) and polyacrylate sodium (PAAS) were blended with EN and prepared by electrospinning. Scanning electron microscopy (SEM) revealed PVA/PAAS/EN nanofibers with good morphology, and that their EN activity and mechanical properties were enhanced. When the ultrasonication time was 15 min and 15% EN was added, the nanofibers had optimal mechanical, light transmittance, and barrier properties. Besides, the release behavior of nisin from the nanofibers fit the Korsemeyer–Peppas (KP) model, a maximum nisin release rate of 85.28 ± 2.38% was achieved over 16 days. At 4 °C, the growth of Escherichia coli and Staphylococcus aureus was inhibited for 16 days in nanofibers under different ultrasonic times. The application of the fiber in food packaging can effectively inhibit the activity of food microorganisms and prolong the shelf life of strawberries, displaying a great potential application for food preservation. [ABSTRACT FROM AUTHOR]

In this study, biopolymer-based antimicrobial fibrous membranes constituted by polylactic acid (PLA) and ultrasonically dispersed ZnO nanoparticles (NPs) were developed by electrospinning. The morphology, mechanical properties, thermodynamics and antimicrobial properties of membranes with different ZnO NPs content were comprehensively studied. The results showed that the best performance was achieved when the content of ZnO content was 0.5 wt% (PLA/ZnO-0.5%). Specifically, the tensile strength and elongation at break of the composite membrane were 6.85 ± 0.19 MPa and 74.90 ± 0.59%, respectively, and the inhibition zones of Escherichia coli and Staphylococcus aureus were 15.02 ± 0.18 mm and 14.74 ± 0.06 mm, respectively. In addition, an appropriate ultrasonication time of 45 min improved the thermal, ultraviolet (UV) barrier, and antibacterial properties of the composite membrane. At the 45 min ultrasonication time, the inhibition zone of PLA/ZnO-0.5% against Escherichia coli and Staphylococcus aureus was 18.11 ± 0.15 mm and 15.80 ± 0.11 mm, respectively. Therefore, PLA/ZnO-0.5% can be applied in food packaging to provide an antibacterial effect and UV light barrier. • The influence of sonication times was investigated on PLA/ZnO nanofibers preparation. • Combination of ultrasound and ZnO can improve physicochemical properties of nanocomposite. • Ultrasonication has great potential to improve the antimicrobial properties of nanofibers. [ABSTRACT FROM AUTHOR]