Development of a chitosan and whey protein-based, biodegradable, colorimetric/fluorescent dual-channel monitoring label for real-time sensing of shrimp freshness.

To address the growing and urgent need for quick and accurate food spoilage detection systems as well as to reduce food resource wastage, recent research has focused on intelligent bio-labels using pH indicators. Accordingly, we developed a dual-channel intelligent label with colorimetric and fluorescent capabilities using black lycium anthocyanin (BLA) and 9,10-bis(2,2-dipyridylvinyl) anthracene (DSA4P) as colorimetric and fluorescent indicators within a composite film consisting of chitosan (Cs), whey protein (Wp), and sodium tripolyphosphate (STPP). The addition of STPP as a cross-linking agent significantly improved the hydrophobicity, mechanical properties, and thermal stability of the Cs/Wp composite films under low pH conditions. After the incorporation of BLA and DSA4P, the resulting dual-channel intelligent label (Cs/Wp/STPP/BLA/DSA4P) exhibited superior hydrophobicity, as indicated by a water contact angle of 78.03°. Additionally, it displayed enhanced mechanical properties, with a tensile strength (TS) of 3.04 MPa and an elongation at break (EAB) of 81.07 %, while maintaining a low transmittance of 28.48 % at 600 nm. After 25 days of burial in soil, the label was significantly degraded, which showcases its eco-friendly nature. Moreover, the label could visually detect color changes indicating volatile ammonia concentrations (25-25,000 ppm). The color of the label in daylight gradually shifted from brick-red to light-red, brownish-yellow, and finally light-green as the ammonia concentration increased. Correspondingly, its fluorescence transitioned from no fluorescence to green fluorescence with increasing ammonia concentration, gradually intensifying under 365-nm UV light. Furthermore, the label effectively monitored the freshness of shrimp stored at temperatures of 4 °C, 25 °C, and - 18 °C. Thus, the label developed in this study exhibits significant potential for enhancing food safety monitoring.

Intelligent biogenic pH-sensitive and amine-responsive color-changing label for real-time monitoring of shrimp freshness.

BACKGROUND: This study developed an intelligent, pH-sensitive and amine-responsive colorimetric label based on chitosan, whey protein and thymol blue by controlling the pH value of the film-forming solution. The obtained label was used to monitor shrimp freshness in real time. The results of this study offer a new approach for developing highly intelligent biogenic labels for freshness monitoring during seafood preservation and processing. RESULTS: The pH 2.0 chitosan-whey protein-thymol blue (CWT-pH 2.0) label exhibited remarkable properties, including the highest tensile strength (5.90 MPa), excellent thermal stability, low water solubility (27.80%) and highly sensitive color responsiveness. The characterization techniques of scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy confirmed the effective immobilization of thymol blue within the film-forming matrix through hydrogen bonding. Furthermore, the CWT-pH 2.0 label demonstrated visible color changes in the presence of volatile ammonia concentrations ranging from 25 to 25 000 ppm. Consequently, the label successfully facilitated real-time monitoring of shrimp freshness during storage at 4 °C. Importantly, the release rate of thymol blue from the label in food simulants was minimal, measuring only 2.53%. CONCLUSION: The CWT-pH 2.0 label exhibits significant potential as a highly intelligent biogenic label for freshness monitoring in seafood preservation and processing. © 2023 Society of Chemical Industry.

Eco-Friendly Semi-Interpenetrating Polymer Network Hydrogels of Sodium Carboxymethyl Cellulose/Gelatin for Methylene Blue Removal.

The present work describes the potential application of environmentally friendly sodium carboxymethylcellulose/gelatin (CMC/Gel) semi-interpenetrating hydrogels prepared by citric acid as a nontoxic cross-linking agent to adsorb dyes. The prepared hydrogels were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA/DTG), and swelling study. The adsorption performance of CMC/Gel2 (C/G2) hydrogel on methylene blue (MB) was investigated. The results showed the better adsorption conditions: adsorption time of 300 min, initial MB concentration of 500 mg/L, adsorbent dosage of 1.2 g/L, solution pH of 7, and temperature of 30 °C. The adsorption kinetics fit the pseudo-second order kinetics model, and the adsorption isotherm fit the Langmuir isotherm model. The maximum adsorption capacity reached 943.40 mg/g. The adsorption process is a spontaneous exothermic process. After three adsorption-desorption cycles, the removal rate of MB by hydrogel still reached 85%, with good reusability. Consequently, the hydrogel can be used as an environmentally friendly, stable, and efficient adsorbent for dyes in wastewater treatment.

Development and characterization of pectin and chitosan films incorporated with a new cross-linking agent.

BACKGROUND: In this study, a new crosslinking agent (CA) containing whey protein, papin, glycerin, and epigallocatechin gallate (EGCG), was prepared. The effects of CA content (0, 10, 20, 30, and 40%, v/v) on food packaging properties, crystallinity, microstructure, and antioxidant properties of pectin-CA and chitosan-CA composite films were analyzed. The results of this research offer a theoretical basis for engineering improved films for food packing. RESULTS: Pectin-CA (30%) and chitosan-CA (40%) composite films showed the best light transmission, water retention, breathability, plasticity, and antioxidant activity. Scanning electron microscopy revealed that these composite films exhibited a uniform and homogeneous structure without obvious pores. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the amino acids and EGCG in CA were bonded to the film substrate (pectin/chitosan) via electrostatic interactions, hydrogen bonding, and covalent bonding, which led to an improvement in the film's properties. CONCLUSION: The CA has broad application prospects in food packaging as a cross-linking agent and antioxidant. © 2022 Society of Chemical Industry.

Effects of Ultrasound-Assisted Immersion Freezing on the Protein Structure, Physicochemical Properties and Muscle Quality of the Bay Scallop (Argopecten irradians) during Frozen Storage.

In this study, the comparison effects of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power, immersion freezing (IF), and air freezing (AF) on the protein thermal stability, protein structure, and physicochemical properties of adductor muscle of scallop (Argopecten irradians) (AMS) during frozen storage were investigated. Principal component analysis and the Taylor diagram were used to comprehensively analyze all the indicators tested. The results showed that the UIF at 150 W (UIF-150) treatment was the most effective way to delay the quality deterioration of AMS during 90-day frozen storage. This was mainly because, compared to AF and IF treatments, UIF-150 treatment more effectively minimized the changes in the primary, secondary and tertiary structures of myofibrillar proteins, and it preserved the protein thermal stability of AMS by producing small and regular ice crystals in the AMS tissue during the freezing process. Moreover, the results of physicochemical properties indicated that UIF-150 treatment significantly inhibited the fat oxidation and microbiological activities of frozen AMS, and it finally maintained the microstructure and texture of AMS during frozen storage. Overall, UIF-150 has potential industrial application prospects in the rapid freezing and quality preservation of scallops.

Design, synthesis and biological activity of pyrazinamide derivatives for anti-Mycobacterium tuberculosis.

A total of 11 pyrazinamide derivatives were designed and synthesised using pyrazinamide as the lead compound, which was optimised by structural modification with alkyl chains, six-membered rings, and bioisosterism, respectively. The target compounds were synthesised using pyrazinecarboxylic acid as the starting material by acylation, amidation, and alkylation, respectively. Their structures were confirmed by 1H NMR, 13C NMR, HRESIMS, and elemental analysis, respectively. The bioactivities of derivatives were assayed using bacteriostatic experiment and minimum inhibitory concentration experiment. It was showed that the derivatives had good inhibitory effect on Mycobacterium tuberculosis. The biological activity of derivative 1f was the best among all compounds, its antibacterial activity was 99.6%, and the minimum inhibitory concentration was 8.0 µg/mL.

Design, synthesis and bioactivities of Celecoxib analogues or derivatives.

A series of Celecoxib analogues or derivatives were designed and synthesized, and their biological activities were studied. The results of inhibitory activity in vitro proved that compounds 1a, 1h, 1i, 1l and 1p had better inhibitory effect on COX-2, and the selectivity was higher. Among them, the inhibitory activity of compound 1h to COX-2 was IC50=0.049µmol/L and SI >1000. Moreover, the experimental results of anti-inflammatory activity in vivo showed that they had good anti-inflammatory activity and could inhibit the release of PGE-2. Therefore, these compounds have better druggability.

On three-dimensional holographic vector of atomic interaction field analysis for influenza neuraminidase inhibitors.

Influenza is a major respiratory infection associated with significant morbidity in the general population and mortality in elderly and high-risk patients. It is an RNA virus that contains two major surface glycoproteins, neuraminidase and hemagglutinin. These proteins are essential for infection. Neuraminidase has been found to be a potential target to control influenza virus. Here, we have developed three-dimensional holographic vector of atomic interaction field analysis as a new method of quantitative structure-activity relationships for different sets of compounds to understand chemical-biological interactions governing their activities toward influenza neuraminidase. Good results, R = 0.885, SD = 0.848, R(CV) = 0.858 (the maximum) and SD(CV) = 0.934 (the minimum), showed that holographic vector of atomic interaction field analysis can be applicable to molecular structural characterization and biological activity prediction and quantitative structure-activity relationship model had favorable stability and prediction capability.

Recognition for avian influenza virus proteins based on support vector machine and linear discriminant analysis.

Total 200 properties related to structural characteristics were employed to represent structures of 400 HA coded proteins of influenza virus as training samples. Some recognition models for HA proteins of avian influenza virus (AIV) were developed using support vector machine (SVM) and linear discriminant analysis (LDA). The results obtained from LDA are as follows: the identification accuracy (R ia) for training samples is 99.8% and R ia by leave one out cross validation is 99.5%. Both R ia of 99.8% for training samples and R ia of 99.3% by leave one out cross validation are obtained using SVM model, respectively. External 200 HA proteins of influenza virus were used to validate the external predictive power of the resulting model. The external R ia for them is 95.5% by LDA and 96.5% by SVM, respectively, which shows that HA proteins of AIVs are preferably recognized by SVM and LDA, and the performances by SVM are superior to those by LDA.