Chitosan/zein-based sustained-release composite films: Fabrication, physicochemical properties and release kinetics of tea polyphenols from polymer matrix.

This study investigated the properties of chitosan/zein/tea polyphenols (C/Z/T) films and analyzed the release kinetics of tea polyphenols (TP) in various food simulants to enhance the sustainability and functionality of food packaging. The results revealed that TP addition enhanced the hydrophilicity, opacity and mechanical properties of film, and improved the compatibility between film matrix. 1.5 % TP film showed the lowest lightness (76.4) and the highest chroma (29.1), while 2 % TP film had the highest hue angle (1.5). However, the excessive TP (above 1 % concentration) led to a decrease in compatibility and mechanical properties of film. The TP concentration (2 %) resulted in the highest swelling degree in aqueous (750.6 %), alcoholic (451.1 %), and fatty (6.4 %) food simulants. The cumulative release of TP decreased to 16.32 %, 47.13 %, and 5.87 % with the increase of TP load in the aqueous, alcoholic, and fatty food simulants, respectively. The Peleg model best described TP release kinetics. The 2 % TP-loaded film showed the highest DPPH (97.13 %) and ABTS (97.86 %) free radical scavenging activity. The results showed TP release influenced by many factors and obeyed Fick's law of diffusion. This study offered valuable insights and theoretical support for the practical application of active films.

Development of pH-freshness smart label based on gellan gum film incorporated with red cabbage anthocyanins extract and its application in postharvest mushroom.

Novel colorimetric films based on gellan gum (GG) containing red cabbage anthocyanins extract (RCAE) were prepared as pH-freshness smart labels for real-time visual detection of mushroom freshness. The GG/RCAE films had excellent pH and ammonia sensitivity. The GG/RCAE-0.2-0.3 films had the highest sensitivity to acetic acid. The SEM micrographs, AFM images, FT-IR and XRD spectra demonstrated that RCAE were successfully combined into the film-forming substrate. The incorporation of RCAE resulted in the increase of thermal stability, opacity and surface hydrophobicity of films. Meanwhile, the GG/RCAE-0.2 film exhibited stronger tensile strength and excellent color stability at 4℃. The color changes of GG/RCAE-0.2 film were visually easier to distinguish during the storage of mushroom. The results showed the GG/RCAE films could be used as pH-freshness smart labels to detect the freshness of fruits and vegetables.

Preparation, characterization and application of pH-responsive smart film based on chitosan/zein and red radish anthocyanin.

This research was aimed at developing a novel pH-responsive smart film made of chitosan, zein and red radish anthocyanin (RRA). The morphology, interaction, crystallization, thermal stability, physiochemical properties and pH sensitivity of films were analyzed. The smart film was applied to monitor the freshness of mushroom (Agaricus bisporus). The results of morphology (SEM) and spectrum (FT-IR and XRD) indicated that the incorporation of RRA could enhance the interaction between polymer matrix. The addition of RRA had no significant effect on the thermal stability of films. The chitosan/zein/red radish anthocyanin (C/Z/R) films exhibited higher tensile strength, Young's modulus, hydrophobicity, antioxidant activity and lower elongation at break. The C/Z/R films had stronger water vapor and gas barrier capacity. The C/Z/R films showed a pH-sensitive color variation from red (pH 2) to green (pH 12) and good reversibility under alkaline and acidic environment. The prepared smart film could be successfully used for the quality monitoring of mushroom.

Bacterial community dynamics and metabolic functions prediction in white button mushroom (Agaricus bisporus) during storage.

White button mushroom (Agaricus bisporus) is rich in nutritional value, but it is easily infected by microorganisms during storage, which leads to spoilage and shortens the storage time. In this paper, A. bisporus at different storage times was sequenced by Illumina Novaseq 6000 platform. QIIME2 and PICRUSt2 were used to analyze the changes of bacterial community diversity and predict metabolic functions during storage of A. bisporus. Then, the pathogenic bacteria were isolated and identified from the spoilt samples of A. bisporus with black spot. The results showed that the bacterial species richness of A. bisporus surface gradually decreased. 2,291 ASVs were finally obtained through DADA2 denoising, belonging to 27 phyla, 60 classes, 154 orders, 255 families and 484 genera. The abundance of Pseudomonas on the surface of fresh A. bisporus sample was 22.8%, which increased to 68.7% after 6 days of storage. The abundance significantly increased and became a dominant spoilage bacterium. In addition, A total of 46 secondary metabolic pathways belonging to 6 categories of primary biological metabolic pathways were predicted during storage of A. bisporus, and metabolism (71.8%) was the main functional pathway. Co-occurrence network analysis revealed that the dominant bacterium Pseudomonas was positively correlated with 13 functional pathways (level 3). A total of 5 strains were isolated and purified from diseased A. bisporus surface. The test of pathogenicity showed that Pseudomonas tolaasii caused serious spoilage of A. bisporus. The study provided a theoretical basis for the development of antibacterial materials to reduce related diseases and prolong the storage time of A. bisporus.

Preparation and characterization of chitosan/zein film loaded with lemon essential oil: Effects on postharvest quality of mushroom (Agaricus bisporus).

In this study, different concentrations of lemon essential oils (LEO) were incorporated into chitosan/zein complex film (C/Z/L films) to improve its antioxidant and antimicrobial capacity, and the effects of C/Z/L films on mushroom quality were evaluated at 4 °C for 12 d. The antioxidant and antimicrobial activity of C/Z films were effectively improved by addition of LEO in a concentration-dependent manner. What's more, EAB value and gas permeability increased while TS value and water vapor permeability decreased upon the gradual increase of LEO content. During the entire storage, C/Z/L films were effective in suppressing PPO and POD activity of mushrooms as well as inhibiting the growth of microorganism. Mushrooms packaged with the film containing 6% LEO showed the lowest browning index and respiration rate. In addition, the C/Z/L film-treated mushrooms exhibited higher antioxidant capacity and more satisfactory texture properties. The results of our study presented that C/Z active film loaded with LEO could be used to maintain the postharvest quality of mushrooms.