A colorimetry-enhanced tri-functional film with high stability by polyphenol-anthocyanin co-pigmentation/conjugate: New prospect for active intelligent food packaging.

A highly stable "tannin-anthocyanin conjugated" trifunctional active intelligent film was developed by incorporating bilberry anthocyanins (BA) as an indicator and tannin acids (TA) as a co-pigment into a sodium alginate-carrageenan polysaccharide matrix (SC-BA/TA). The doping of TA conferred outstanding antioxidant (DPPH scavenging rate > 90%) and antibacterial properties to the film, particularly effective against S. aureus. The SC-BA/TA films effectively blocked UV rays (close to 0%, effectively impeding most UVA, as well as nearly all UVC and UVB) within the range of 200-320 nm. The TA-BA co-pigment effect significantly improved the anthocyanins' storage and color stability (retention rate > 70% under UV and natural light conditions). TA forms conjugate with anthocyanins by π-π stacking and hydrogen bonding interactions with co-pigmentation rate increases of 10.5% and 11.0% for pH 2 and pH 3, respectively. The film exhibited good responsiveness to volatile amines within 4 min, and offered real-time monitoring of beef freshness, as indicated by visualizing color changes (from red to dark yellow color). Furthermore, the integration of the film's RGB value with beef quality via a smartphone App effectively reduces the variability in visual recognition among individuals. To sum up, composite films based on the "tannin-anthocyanin conjugate" approach hold great potential in the field of food freshness monitoring, opening new possibilities for the development of highly stable active smart packaging films.

Study on preservation and monitoring effect of sodium alginate-konjac glucomannan films loaded with tea polyphenols and Lycium ruthenicum anthocyanins.

To investigate the efficacy of sodium alginate-konjac glucomannan (SA-KGM) films with anthocyanins (LRA) and tea polyphenols (TP) in meat, beef and grass carp were selected as representative meat products for preservation and freshness monitoring experiments at 4 °C. Concurrently, storage experiments of the films were conducted in this controlled environment. The results of the storage experiment showed that the films delayed meat spoilage by 2-4 days, nearly doubling the preservation time compared to the blank control. Additionally, the film exhibited significant capability to monitor the spoilage process of beef and grass carp. It was revealed by curve fitting analysis that there was a significant correlation between the color change of the film and the spoilage index of the meat. Throughout the storage experiment with the film, it was observed that moisture significantly influenced the microstructure and bonding situation of the films, thereby impacting their mechanical and barrier properties. However, the films were still able to maintain satisfactory physicochemical properties in general. The above findings were crucial in guiding the promotion of the film within the food preservation industry.

Development of novel carboxymethyl cellulose/gelatin-based edible films with pomegranate peel extract as antibacterial/antioxidant agents for beef preservation.

Novel antioxidant and antibacterial composite films were fabricated by incorporating pomegranate peel extract (PPE) into gelatin and carboxymethyl cellulose matrices. Increasing PPE concentration significantly (p < 0.05) altered physical properties and improved UV (decrease in light transmission 87.30 % to 9.89 % at 400 nm) and water resistance, while FTIR and molecular docking results revealed hydrogen bonding between PPE and film matrix. PPE incorporation enhanced antioxidant activity up to 84.15 ± 0.12 % and also restricted gram-positive and gram-negative bacterial growth by 72.4 % and 65.9 % respectively after 24 h, measured by antimicrobial absorption assays. For beef packaging applications at refrigeration temperatures, PPE films were most effective at extending shelf-life up to 3 days, as evidenced by reduced total viable counts, total volatile basic nitrogen, weight loss, and pH changes compared to control films. Therefore, these antioxidant and antibacterial films have potential applications in food packaging to protect against mechanical stress, light exposure, microbial spoilage, and oxidative free radicals.

Reinforcing effect of ε-polylysine-carboxymethyl chitosan nanoparticles on gelatin-based film: Enhancement of physicochemical, antioxidant, and antibacterial properties.

The development and application of antibacterial film were highly anticipated to prevent food spoilage caused by bacteria. In this investigation, antibacterial and antioxidant functionalized gelatin-based film was formed with the incorporation of oregano essential emulsion Pickering emulsion (OPE). ε-Polylysine-Carboxymethyl Chitosan nanoparticles (CMCS-ε-PL) composed of different mass ratios of CMCS and ε-PL were orchestrated by electrostatic forces and hydrogen bonding, which effectively acted as a stabilizer for OPE. The design of different mass ratios of CMCS and ε-PL in CMCS-ε-PL has a deep effect on the structure and functional properties of OPE and film. It successfully improved the encapsulation efficiency of OPE from 49.52 % to 79.83 %. With the observation of AFM images, the augmentation of surface roughness consequent to OPE incorporation can be relieved by the increased contention of ε-PL in CMCS-ε-PL. Meanwhile, the mechanical properties, barrier properties, anti-oxidation, and antibacterial properties of the films were improved with the incorporation of the above OPE. In particular, a synergistic antibacterial activity between ε-PL and OEO in the film was demonstrated in this study and the mechanism of enhanced antibacterial activity was elucidated by examining the integrity of bacteria cell membrane. The film unequivocally demonstrated its ability to appreciably prolong the shelf life of both beef and strawberries with excellent antioxidant and antibacterial properties.

Intelligent active films of sodium alginate and konjac glucomannan mixed by Lycium ruthenicum anthocyanins and tea polyphenols for milk preservation and freshness monitoring.

To achieve real-time monitoring of food freshness, a pH-responsive film based on sodium alginate-konjac glucomannan loaded with Lycium ruthenicum anthocyanins (LRA) was prepared, with the addition of tea polyphenols (TP) to enhance the stability of LRA. The surface structure of the films was observed by AFM. The results of FTIR and molecular docking simulation showed that LRA and TP were bound to polysaccharide by hydrogen bonds. The mechanical properties, barrier properties, and antioxidant/antibacterial properties of the films were significantly improved and the films showed obvious color response to pH. Notably, the AFM images showed TP and LRA could lead to more severe damage to the bacterial structure. The results of molecular docking simulation suggested that TP and LRA could act on different components of the bacterial cell wall, indicating their synergistic mechanism in antimicrobial activity. Moreover, the stability of LRA was improved due to the interactions of TP and polysaccharides with LRA. The aggregates formed by TP and LRA were clearly observed by AFM. Finally, the film showed excellent preservation and freshness monitoring effect in milk. In conclusion, TP-LRA-SA-KGM intelligent film exhibited excellent performance and represented a promising novel food packaging material with potential applications.

Composite films of sodium alginate and konjac glucomannan incorporated with tea polyphenols for food preservation.

At present, food waste has become a serious issue and the use of petroleum-based food packaging films has resulted in a series of potential hazards. Therefore, more attention has been focused on the development of new food packaging materials. The polysaccharide-based composite film loaded with active substances considered to be an excellent preservative material. A novel packaging film based on sodium alginate and konjac glucomannan (SA-KGM) blended with tea polyphenols (TP) was prepared in the present study. The excellent microstructure of films was shown by atomic force microscopy (AFM). It was indicated by FTIR spectra that the components could interact with each other through hydrogen bonds, which was also confirmed by molecular docking simulation. Meanwhile, the mechanical properties, barrier property, oxidation property, antibacterial activity, and stability of the structure of the TP-SA-KGM film were significantly improved. The AFM images and results of molecular docking simulation indicated that TP could affect the cell wall of bacteria by acting with peptidoglycan. Finally, the film showed excellent preservation effects in both beef and apples, which suggested that TP-SA-KGM film could be a novel bioactive packaging material with wide application potential in food preservation.