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.

Effect of ethanol content on rheology of film-forming solutions and properties of zein/chitosan film.

The paper focused on the role of ethanol on rheological properties of zein/chitosan film-forming solutions, thermo-mechanical and structural characterization of films. The steady rheological results indicated that the film-forming solutions showed non-Newtonian behavior, and ZC-3 solution (zein treated with 90% ethanol and chitosan dissolved with acetic acid) had higher flow index (0.882±0.003). Based on dynamic rheological analysis, ZC-3 solution showed the highest G' value and the crossover point at the lowest frequency, representing the strongest entanglement and hydrogen bonding. ZC-3 film showed the highest tensile strength and elongation at break (16.72MPa and 76.80%). The film prepared from high ethanol content improved water vapor, oxygen and carbon dioxide barrier properties. The X-ray diffraction (XRD) demonstrated zein and chitosan had good compatibility. Differential scanning calorimetric (DSC) indicated that the endothermic peak temperature of ZC-3 film was 148.83°C. The thermogravimetric (TGA) results indicated that ZC-3 film had excellent thermal stability.

Alteration of behavioral changes and hippocampus galanin expression in chronic unpredictable mild stress-induced depression rats and effect of electroacupuncture treatment.

To explore new noninvasive treatment options for depression, this study investigated the effects of electric acupuncture (EA) for depression rat models. Depression in rats was induced by unpredictable chronic mild stress (UCMS) combined with isolation for 21 days. Eighteen male Sprague-Dawley rats were randomly assigned into three groups: control, model, and EA groups. Rats were treated by EA once daily for 21 days. The results showed that body weight and sucrose consumption were significantly increased in EA group than in the model group. The crossing numbers and rearing numbers in the open field test significantly decreased in the model group but not in the EA group. And EA treatments upregulated levels of hippocampus galanin (Gal) in UCMS rats back to relative normal levels. The present study suggested that EA had antidepressant effects on UCMS model rats. The potential antidepressant effect may be related to upregulating Gal expression in hippocampus.

[Effects of electroacupuncture on circadian rhythm of temperature and melatonin in depression rats model induced by chronic stress].

OBJECTIVE: To observe the effects of electroacupuncture (EA) on circadian rhythm of temperature and melatonin (MT) in depression rats model induced by chronic stress, so as to explore the biological mechanism of EA for depression. METHODS: Twenty-four SD rats were randomly divided into a control group, a model group and an EA group, 8 cases in each one. Rats in the control group were treated with normal diet for 21 days without any treatment. In the model and EA group, rat model was established by chronic unpredictable stress combined with solitarily feeding method, and rats in the EA group was treated with EA at "Baihui" (GV 20), "Yintang" (GV 29) 1 h before stress stimulation everyday, 2 Hz in frequency and intensity was favorable with the head of rat slightly shivering. The needles were retained for 20 min, once a day for totally 21 days. After EA treatment, open-field experiment was adopted to observe the behavioral improvement; the rats temperatures were monitored at six time points (2:00, 6:00, 10:00, 14:00, 18:00, 22:00) and orbital blood sampling was collected. The level of serum MT was tested by enzyme linked immunosorbent assay. The circadian rhythm changes of temperature and serum MT in each group were compared. RESULTS: The numbers of horizontal movement and vertical movement in the model group were obviously lower than those in the control group (both P < 0.05), while those in the EA group were significantly improved compared with those in the model group (both P < 0.01). The circadian rhythm of temperature and MT disappeared in the model group, which was improved into normal level after EA treatment. CONCLUSION: The electroacupuncture has regulation effects on circadian rhythm of temperature and melatonin in depression rat model induced by chronic stress.