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Visual indicator bi-layer films were manufactured incorporating κ-carrageenan, butterfly pea flower anthocyanin, varying Nano‑titanium dioxide (TiO 2 ) content and agar for Penaeus chinensis (Chinese white shrimp) freshness detection. The κ-carrageenan-anthocyanin (CA) layer served as indicator, while the TiO 2 -agar (TA) layer functioned as the protective layer to improve the photostability of film. The bi-layer structure was characterized by scanning electron microscopy (SEM). The TA2-CA film had the best tensile strength with a value of 17.8 MPa and the lowest water vapor permeability (WVP) value of bi-layer films was 2.98 × 10 -7  g.m -1 .h -1 .pa -1 . The bi-layer film protected anthocyanin against exudation when immersed in aqueous solution of varying pH. The TiO 2 particles filled the pores of the protective layer, increasing the opacity from 1.61 up to 4.49 significantly improving the photostability with a consequent slight color change under illumination of UV/visible light. Under UV irradiation, the TA2-CA film had no significant color change with a ΔE value of 4.23. Finally, the TA2-CA films showed an obvious color change from blue to yellow green in the early stages of Penaeus chinensis putrefaction (≤48 h) then the color change and Penaeus chinensis freshness were well correlated (R 2  = 0.8739)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Smart packaging systems with multiple functions have recently received great attentions. In this study, a bilayer film with antibacterial activity and indicating ability was developed by electrospinning method for simultaneously preserving and monitoring Lateolabrax japonicus freshness. The lower layer, serving as the antibacterial layer, was composed of zein (ZN), gelatin (GA) and carvacrol (CA). The upper layer, working as the indicating layer, was composed of chitosan (CS), polyvinyl alcohol (PVA) and blueberry anthocyanins (BBA). It was found that the film had strong antibacterial activity against common foodborne bacteria, suggesting it could prolong the shelf life of fish by 24 h during storage at 4 °C. Meanwhile, the bilayer film was sensitive to NH3, with a LOD value of 0.03357 μM. It exhibited a red-to-blue color change when was used to monitor the freshness of fish, due to the increasing content of volatile amines of fish. [ABSTRACT FROM AUTHOR]

High-stability bi-layer films were prepared by incorporating anthocyanin-loaded liposomes into carrageenan and agar (A-CBAL) for non-destructive shrimp freshness monitoring. The encapsulation efficiency of the anthocyanin-loaded liposomes increased from 36.06% to 46.99% with an increasing ratio of lecithin. The water vapor transmission (WVP) of the A-CBAL films, with a value of 2.32 × 10−7 g · m−1 · h−1 · pa−1, was lower than that of the film with free anthocyanins (A-CBA). The exudation rate of the A-CBA film reached 100% at pH 7 and pH 9 after 50 min, while the A-CBAL films slowed down to a value lower than 45%. The encapsulation of anthocyanins slightly decreased the ammonia sensitivity. Finally, the bi-layer films with liposomes successfully monitored shrimp freshness with visible color changes to the naked eye. These results indicated that films with anthocyanin-loaded liposomes have potential applications in high-humidity environments. [ABSTRACT FROM AUTHOR]

Anthocyanins-based colorimetric volatile amines sensors have recently received great attention for monitoring meat and fish freshness. However, most of the sensors suffered from anthocyanins leaching problems in humid packaging environments, severely limiting their indication ability. The present study developed a hydrogel-in-oleogel bigel to protect anthocyanins from leaching. The internal hydrogel was composed of water, agar and purple sweet potato anthocyanins (PSPA), and the external oleogel was made up of sunflower oil, beeswax and glyceride monooleate (GMO). The agar concentration and water-to-oil-phase volume ratio (W/O) were optimized to be 1.0% and 2:8, respectively. The optimal pH value of hydrogel was determined to be 6.50, taking into consideration of the gas sensitivity and color stability of the bigel. The bigel was extruded onto polyvinylidene fluoride (PVDF) film through a 3D printing method to form the composite film. The results of the study revealed that PVDF-bigel composite film showed good stability in water, indicative of strong anti-leaching properties. Meanwhile, the PVDF-bigel film was sensitive to trimethylamine (TMA) with a limit of detection of 2.52 μM. The PVDF-bigel film was subjected to in-situ and real-time monitor beef and salmon freshness. The film exhibited a red-to-purple color change upon reacting with volatile amines generated from beef and salmon. Henceforth, this study presented a new method to develop anthocyanins-based colorimetric gas sensors for intelligent food packaging. [Display omitted] • A hydrogel-in-oleogel bigel containing anthocyanins was developed. • The bigel with a W/O ratio of 2:8 showed good rheological properties for 3D printing. • The bigel showed good color stability in water, indicating its anti-leaching ability. • The bigel was sensitive to TMA with LOD of 2.52 μM. • The bigel used to monitor beef and salmon freshness showed visible color changes. [ABSTRACT FROM AUTHOR]

Active agar (AG) bilayer films with bioactive capability and electrochemical writing property were developed for improving the postharvest quality of the banana. The antioxidant and antimicrobial capacity of the films were enhanced with the incorporation of red radish extract (RRE) and neem essential oil (NEO) into AG lower layer. The barrier and mechanical properties, retention of total anthocyanin and NEO content in the bilayer films were effectively improved with addition of TiO 2 into the AG upper layer. Multicolor patterns were successfully written on the bilayer film containing RRE. The AG-TiO 2 +AG-RRE-NEO bilayer film exhibited the optimal preservations on banana fruits during the storage period, based on the characterization by fruits appearance, senescent spotting symptom, microbial analysis, weight loss and firmness. Thus, the AG-TiO 2 +AG-RRE-NEO bilayer film was expected to be a multifunction packaging material for banana preservation. [Display omitted] • Active agar bilayer films were developed successfully. • Red radish extract (RRE) and neem essential oil (NEO) improved the antioxidant and antimicrobial capacity of the films. • TiO 2 nanoparticles enhanced the retention of total anthocyanin and NEO content in the bilayer films. • Multicolor patterns were successfully written on the active agar bilayer film containing RRE. • Active agar bilayer film expected to be a multifunction packaging material for banana preservation. [ABSTRACT FROM AUTHOR]

• Bilayer films were developed using agar, anthocyanins, gellan gum and TiO 2. • TiO 2 improved the illumination stability of the film. • Gellan gum-TiO 2 contributed to the electrochemical writing on the film. • The bilayer film was sensitive to NH 3 , trimethylamine and dimethylamine. • The bilayer film showed color changes during spoilage of pork and silver carp. Amine-responsive bilayer films were developed by using agar (AG), anthocyanins (AN), gellan gum (GG) and TiO 2 nanoparticles for visual monitoring of meat spoilage. The AG-AN layer worked as the sensing layer to volatile amines, while GG-TiO 2 layer served as the light barrier layer and simultaneously the conducting layer to improve the illumination stability and electrochemical writing ability of the AG-AN layer, respectively. The Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) spectra indicated the successful fabrication of bilayer films. Illumination experiments showed that the incorporation of TiO 2 in the GG-TiO 2 layer significantly improved the illumination stability of AN in the AG-AN layer. Meanwhile, electrochemical writing process could be easily conducted on the AG-AN layer in the presence of GG-TiO 2 layer, indicating the feasibility of ink-free printing on bilayer biopolymer films. The AG-AN/GG-2%TiO 2 film presented a limit of detection of 0.018 mM to trimethylamine (TMA), a typical basic gas generated during meat spoilage. Based on its good illumination stability and sensing ability to basic gases, the AG-AN/GG-2%TiO 2 film exhibited rose red-to-green color changes along with the spoilage of pork and silver carp, indicating its great potential for monitoring meat spoilage in intelligent food packaging. [ABSTRACT FROM AUTHOR]