Volatile Amines Research Articles

New Cyanostyrylcopillar[5]arene Derivative: Synthesis, Photophysical Study, Chromogenic Detection of Aliphatic Amines, and Biofilm-Antibiofilm Activity.

The synthesis, characterization, and application of a new cyanostyrylcopillar[5]arene 1 is reported. Single-crystal X-ray diffraction and other spectroscopic techniques confirm the identity of the new copillar 1. The X-ray diffraction study reveals that the copillar 1 exhibits a 1D supramolecular chain in the solid state involving π···π interactions along the crystallographic c-axis and 1D chains are further connected by interchain C-H···π interactions to establish 2D supramolecular layers within the crystallographic bc-plane. 2D supramolecular chains on further packing introduce a 3D structure with void spaces filled with hexane molecules. Through minimal deviation in the dihedral angle, the cyano-substituted ethylenic group in 1 shows a conjugation with the phenolic -OH, favoring intramolecular bond conjugation (ITBC) and colorimetrically detects the aliphatic amines over aromatic amines in CH3CN. Among the aliphatic amines, tertiary amines are differentiated from primary and secondary amines by the naked eye through color change. Both in solution and solid states, 1 displays vapor phase detection of volatile aliphatic amines. Antibacterial activity analysis shows that while 1 exhibits the antibiofilm action against Gram-positive pathogenic bacteria, Staphylococcus aureus, it promotes biofilm formation by Gram-negative pathogenic bacteria, Pseudomonas aeruginosa.

Green active coating from chitosan incorporated with spontaneous cinnamon oil nanoemulsion: Effects on dried shrimp quality and shelf life

Green active film from chitosan (C) incorporated with spontaneous emulsified cinnamon oil nanoemulsion (CONE; droplet size of 79.27 nm and polydispersity index of 0.27) was developed. The obtained chitosan film containing CONE (C + CONE) had tensile elongation and light protective effect higher than C film due to the incorporation of bioactive compounds from cinnamon oil as proven by Fourier Transform Infrared Spectroscopy. The effect of C + CONE as active edible coating on the physical, chemical, and microbiological properties of dried shrimp was then investigated. The quality of samples coated with C + CONE (DS + C + CONE) was compared to those coated with C (DS + C) and without coating (DS). In this study, C + CONE could enhance astaxanthin content and reduce lipid oxidation in dried shrimp. During 6 weeks of storage, C + CONE was found to be an effective antimicrobial coating that significantly inhibited growth of bacteria, delayed lipid oxidation and retarded the production of volatile amines in dried shrimp. DS + C + CONE had lower malonaldehyde equivalents (0.52 mg/kg oil), trimethylamine (11.74 mg/100 g), total volatile base nitrogen (84.33 mg/100 g) and total viable count (4.80 Log CFU/g), but had higher astaxanthin content (12.53 ± 0.12 μg/g) than DS and DS + C. The results suggested that the developed C + CONE coating has potential to be used as active coating for preserving food quality.

A dual emitting CsPbBr3/Eu-BDC composite as a ratiometric photoluminescent turn-on probe for aliphatic amine sensing.

The impressive photoluminescence properties of all inorganic cesium lead halide perovskite quantum dots (PeQDs) make them highly intriguing for fluorescence chemosensor applications. Herein, a ratiometric dual emitting perovskite-based sensor was designed by synthesizing fluorescent CsPbBr3 PeQDs in situ within a matrix of Eu-BDC (Eu(III) benzene-1,4-dicarboxylate). The results presented here establish the suggested sensor's quick and selective turn-on PL response to volatile primary aliphatic amine derivatives. In the presence of amines, the designed CsPbBr3/Eu-BDC sensor exhibits an enhancement of the PL signal of CsPbBr3 at 518 nm and the Eu-BDC signal at 615 nm served as a standard for constructing the ratiometric sensing system. Thereby, a visual color change from red to green was observed with the incremental addition of methylamine to the probe. A low detection limit of 0.083 ppm was determined for methylamine. In both the solution and vapor phases, this ratiometric sensor responds to a variety of primary aliphatic amines with very quick and strong fluorescence. Moreover, the sensor was effectively used for monitoring meat spoilage owing to the emission of biogenic amine vapor from meat products.

Development, characteristics and biological activities of bilayer composite film based on gelatin/κ-carrageenan loading curcumin and ε-polylysine

Using curcumin and epsilon-polylysine (ε-PL) as functional ingredients, one bilayer composite film was prepared by flow casting method using gelatin and κ-carrageenan as the outer- and inner-film layers, respectively. Compared with the inner κ-carrageenan film loading 3 wt% curcumin and 0.1% ε-PL (01CF) or 3 wt% curcumin and 0.3% ε-PL (03CF), the transparency, tensile, and water contact angle of the bilayer composite film were significantly increased. X-ray diffraction results revealed that the inner film matrix of κ-carrageenan interacted well with curcumin and ε-PL. Scanning electron microscopy observed that the cross-sectional surface of the inner and outer layers in the bilayer composite film was smooth and had good compatibility. In atomic force microscopy image, the inner surface of the bilayer composite film had lower root mean square roughness and average roughness than the outer film surface. The crystallinity of curcumin in the bilayer composite film loading 0.3% ε-PL was dramatically reduced in confocal laser scanning microscope images compared to that of the composite film with 0.1% ε-PL addition. The bilayer composite film demonstrated good scavenging activity on DPPH radical with inhibition rate >65%, and showed strong inhibition effect on the spoilage bacteria derived from Penaeus vannamei. Furthermore, the bilayer composite film showed sensitive response to volatile amines by visible color changes from yellowish to reddish brown. In conclusion, the prepared bilayer composite film could have potential application prospects in the field of natural active food packaging materials for shrimp products.

Electrospun cellulose nanofibers immobilized with anthocyanin extract for colorimetric determination of bacteria

A novel smart biochromic textile sensor was developed by immobilizing anthocyanin extract into electrospun cellulose acetate nanofibers to detect bacteria for numerous potential uses, such as healthcare monitoring. Red-cabbage was employed to extract anthocyanin, which was then applied to cellulose acetate nanofibers treated with potassium aluminum sulfate as a mordant. Thus, nanoparticles (NPs) of mordant/anthocyanin (65–115 nm) were generated in situ on the surface of cellulose acetate nanofibrous film. The pH of a growing bacterial culture medium is known to change when bacteria multiply. The absorbance spectra revealed a bluish shift from 595 nm (purple) to 448 nm (green) during the growth of Gram-negative bacteria (E. coli) owing to the discharge of total volatile basic amines as secretion metabolites. On the other hand, the absorption spectra of a growing bacterial culture containing Gram-positive bacteria (L. acidophilus) showed a blue shift from 595 nm (purplish) to 478 nm (pink) as a result of releasing lactic acid as a secretion metabolite. Both absorbance spectra and CIE Lab parameters were used to determine the color shifts. Various analytical techniques were utilized to study the morphology of the anthocyanin-encapsulated electrospun cellulose nanofibers. The cytotoxic effects of the colored cellulose acetate nanofibers were tested.

Intramolecular charge transfer-induced fluorochromic covalent organic frameworks for high speed on-line monitoring of volatile amines

Direct and visual evaluation of volatile amine molecules, a group of hazardous gases and indicators, remains challenge in the fields of chemical industry, environmental detection and food safety. Herein, a convenient and reversible intramolecular charge transfer (ICT)-induced fluorescence-colorimetric approach is proposed for on-line, visual and quantitative monitoring on volatile amines at molecular level through skeletal constructing of cationic pyridinium sites in a carbon-conjugated covalent organic framework (COF). In the presence of volatile amine molecules, the deprotonation of pyridinium sites causes a strong fluorescence enhancement (fluorescence quantum yield > 13 %) and a sharp color change. Specifically, with the reversable pyridinium sites, the COFs-based sensor first exhibits an ultrafast response time (τrise) of 0.65 s to ammonia gas (51.8 ppm), which outperforms reported nanostructure-based ammonia sensors. Meanwhile, through studying the relationship between the total volatile basic nitrogen (TVB-N) and Red/Green/Blue (RGB) outputs of home-made COFs membrane on the food spoilage (fish meat: R2 > 0.9987, shrimp meat: R2 > 0.9917), the protonated TPCH-mOBPy COF is fully verified to work as an on-line fluorochromic probe for visually, AI-intelligently and quantitatively monitoring the generation of volatile amines.

Self-assembled polyacylated anthocyanins on anionic wood film as a multicolor sensor for tracking TVB-N of meat

Available food indicator films do not have a wide color variation and have a low TVB-N carrying capacity. In this study, we generated a high TVB-N-loading multicolor sensor based on self-assembled polyacylated anthocyanins on anionic wood film for tracking meat freshness. We constructed an anionic wood film with H2O2/NaOH to fix Clitoria ternatea anthocyanins via electrostatic interactions. The maximum adsorption capacity was 0.82 mg/g at 50 °C for 4 h. The values of L* , a* and b* were 42.16, 7.30, and − 19.31, respectively. Clitoria ternatea anthocyanins-fixed wood film (CTWF) exhibited four significant color changes under different pH values with high pH-sensitivity. Furthermore, the fixation of Clitoria ternatea anthocyanins enhanced the thermal stability of the anionic wood film as the maximum decomposition temperature of CTWF increased from 323 °C to 336 °C. The water contact angles on the original wood film, anionic wood film, CTWF (Q min), and CTWF (Q max) were 84°, 75°, 55°, and 48° within 1 s, respectively. In addition, CTWF reacted with volatile amines due to its adequate hydrophilicity, changing from violet to green within 3 s at 53% RH under 7.50 mmol/L NH3, which is beneficial for monitoring meat freshness. When TVB-N of 14.56 mg in 100 g of pork approached 15 mg/100 g (GB 2707–2016), the color of CTWF (0.6 cm × 0.6 cm) changed from purple to blue. Therefore, CTWF holds potential as a smart sensor that can monitor the quality of protein-rich foods in real time.

Functional Polymeric Membranes with Antioxidant Properties for the Colorimetric Detection of Amines.

Herein, the ability of highly porous colorimetric indicators to sense volatile and biogenic amine vapors in real time is presented. Curcumin-loaded polycaprolactone porous fiber mats are exposed to various concentrations of off-flavor compounds such as the volatile amine trimethylamine, and the biogenic amines cadaverine, putrescine, spermidine, and histamine, in order to investigate their colorimetric response. CIELAB color space analysis demonstrates that the porous fiber mats can detect the amine vapors, showing a distinct color change in the presence of down to 2.1 ppm of trimethylamine and ca. 11.0 ppm of biogenic amines, surpassing the limit of visual perception in just a few seconds. Moreover, the color changes are reversible either spontaneously, in the case of the volatile amines, or in an assisted way, through interactions with an acidic environment, in the case of the biogenic amines, enabling the use of the same indicator several times. Finally, yet importantly, the strong antioxidant activity of the curcumin-loaded fibers is successfully demonstrated through DPPH● and ABTS● radical scavenging assays. Through such a detailed study, we prove that the developed porous mats can be successfully established as a reusable smart system in applications where the rapid detection of alkaline vapors and/or the antioxidant activity are essential, such as food packaging, biomedicine, and environmental protection.

Polycaprolactone/Anthocyanin-Based Electrospun Volatile Amines Gas Indicator with Improved Visibility by Varying Bi-Solvent Ratio: A Case of Intelligent Packaging of Mackerel.

Electrospun nanofibers have been applied as a new technology for gas indicators in food intelligent packaging. A poly(ε-caprolactone) (PCL)/red cabbage anthocyanin (RCA)-based nanofiber volatile amines gas indicator was developed by applying a bi-solvent of acetic acid (AA) and formic acid (FA) in electrospinning. The visibility of color change was improved from pink to blue, compared to blue to yellow-green, when using a single solvent of AA. The solutes of PCL (12.5, 15, 17.5, and 20%) and RCA (10, 20, 30, and 40%) and the solvents of AA/FA (9:1, 7:3, 5:5, 3:7, and 1:9) were applied in electrospinning under the condition of 12.5 cm, 1.0 mL/h, and 20 kV. The optimal microstructure with the thinnest fiber diameter and constant arrangement without forming NF beads appeared under the 7:3 FA/AA, 15% PCL, and 20% RCA condition. The indicator changed from pink to blue with the values of total color change (ΔE) of 10, 14, and 18 when exposed to the saturated gas of ammonia solutions of 8, 80, and 800 mM, respectively. The indicator was stable and unchanged in color for 28 days when exposed to light at room temperature. In the application to mackerel packaging, the built-in indicator changed from pink to purple regardless of storage temperature when the spoilage point was reached.

Structure-Based Discovery of Mouse Trace Amine-Associated Receptor 5 Antagonists.

Trace amine-associated receptors (TAARs) were discovered in 2001 as new members of class A G protein-coupled receptors (GPCRs). With the only exception of TAAR1, TAAR members (TAAR2-9, also known as noncanonical olfactory receptors) were originally described exclusively in the olfactory epithelium and believed to mediate the innate perception of volatile amines. However, most noncanonical olfactory receptors are still orphan receptors. Given its recently discovered nonolfactory expression and therapeutic potential, TAAR5 has been the focus of deorphanization campaigns that led to the discovery of a few druglike antagonists. Here, we report four novel TAAR5 antagonists identified through high-throughput screening, which, along with the four ligands published in the literature, constituted our starting point to design a computational strategy for the identification of TAAR5 ligands. We developed a structure-based virtual screening protocol that allowed us to identify three new TAAR5 antagonists with a hit rate of 10%. Despite lacking an experimental structure, we accurately modeled the TAAR5 binding site by integrating comparative sequence- and structure-based analyses of serotonin receptors with homology modeling and side-chain optimization. In summary, we have identified seven new TAAR5 antagonists that could serve as lead candidates for the development of new treatments for depression, anxiety, and neurodegenerative diseases.

Bimodal single-atom iron nanozyme biosensor for volatile amine and food freshness detection

Volatile amines (VAs) play a critical role in detecting the freshness of meat. However, the development of nondestructive, real-time, and portable techniques for monitoring VAs remains a challenge. Here, we successfully created a colorimetric-fluorescent dual-signal biosensor for meat freshness detection by using a single-atom iron nanozyme (SAFe-N-C nanozyme) and carbon quantum dots (CDs). The SAFe-N-C nanozyme with high peroxidase-like (POD-like) activity (40.22 U/mg) acts as a catalyst by facilitating the conversion of the colourless reduced state 3,3′,5,5′-tetramethylbenzidine (redTMB) to its oxidized product (oxTMB). Subsequently, the fluorescence signal of the CDs is quenched due to the inner filtering effect (IFE) between oxTMB and CDs. During food spoilage, the generation of VAs results in the reduction of oxTMB, which subsequently recovers the fluorescence of the CDs. As a result, the limits of detection (LOD) for ammonia detection are 0.9840 ppm and 0.0838 ppm within a linear range of 0.5–50 ppm. This colorimetric-fluorescent dual-signal biosensor effectively detects VAs during the spoilage of livestock and poultry meat in a nondestructive and real-time manner. This innovative work overcomes the limitation of single signal output and provides a portable and reliable method for VAs detection, proving to be a significant advancement in meat freshness assessment.

Design of Amine-Containing Nanoporous Materials for Postcombustion CO2 Capture from Engineering Perspectives.

ConspectusCarbon dioxide (CO2) capture and storage (CCS) is a means to enable the continued use of fossil fuels in the short term. In particular, postcombustion CO2 capture has attracted considerable attention because it can be retrofitted into existing power plants and industrial plants. Among various CO2 capture technologies, the absorption of CO2 using aqueous amines has been industrially employed for decades. However, such amine scrubbing technologies have inherent limitations of environmental and health concerns due to volatile amine loss, corrosion, and high energy demands for regeneration. To overcome these limitations, CO2 adsorption using solid adsorbents has emerged as a promising alternative due to its noncorrosiveness and low energy demand. Various amine-containing adsorbents have been synthesized and investigated for postcombustion CO2 capture. These materials are prepared by physically impregnating low-vapor-pressure amine polymers or by chemically grafting amines onto nanoporous materials. A wide variety of amine guests and nanoporous hosts (e.g., SiO2, Al2O3, zeolites, MOFs, and polymers) have been combined to develop advanced CO2 adsorbents.The design of CO2 adsorbents is a multifaceted puzzle that must ultimately consider integration with large-scale CO2 capture processes. Various engineering aspects need to be carefully considered. Unfortunately, a significant proportion of previous studies has primarily focused on the use of novel materials for improving the CO2 adsorption capacity. In this Account, we describe key challenges and solutions to develop energy-efficient and stable amine-containing adsorbents for postcombustion CO2 capture via temperature swing adsorption (TSA). We found that a high CO2 working capacity, often overemphasized in the literature, does not necessarily guarantee a low energy demand for CO2 capture. Suppressing coadsorption of H2O during the CO2 adsorption in humid flue gas is also a significant factor. Amine-containing adsorbents can be degraded through various pathways, including hydrothermal degradation of nanoporous hosts and chemical degradation of amine guests via urea formation and oxidation. To inhibit such degradation pathways, it is extremely important to properly design the nanoporous structures of the hosts and the molecular structures of the amine guests. By combining macroporous silica hosts, poly(ethylenimine) (PEI) functionalized with various alkyl epoxides, and phosphate-based oxidative stabilizers, we could synthesize adsorbents exhibiting low energy demands for CO2 capture and unprecedentedly high thermochemical stability under TSA conditions. The macroporous silica host synthesized by assembling fumed silica particles via spray-drying exhibited high hydrothermal stability and enabled uniform distribution of bulky amine polymers within its pores. The functionalization of PEI with alkyl epoxides converted its primary amines into hindered secondary amines, leading to a significant reduction in energy demand for TSA cycles and a remarkable improvement in long-term stabilities. The oxidative stability of amines could be drastically improved by adding phosphate metal-binding reagents, which can poison ppm-level metal impurities that catalyze amine oxidation. The present discussions will provide important insights into designing practical adsorbents for CO2 capture from engineering perspectives.

Freshness evaluation of grass carp by volatile biogenic amines monitored by secondary electrospray ionization ion mobility spectrometry

In this paper, a secondary electrospray ionization ion mobility spectrometry (SESI-IMS) method using ammonium acerate was evaluated for rapid determination of the various volatile biogenic amine contents in grass carp (Ctenopharyngodon idella). The ammonium ion generated by electrospray ionization source functions as reactant ion to react with volatile biogenic amines in gas phase and separated in the drift tube. The SESI-IMS method requires minimum sample preparation and minimum interferences, and volatile biogenic amines show their unique drift times without overlapping. The content of volatile biogenic amines demonstrates good correlations with storage times at 4 ℃ and 8 ℃ cold storage. It is shown that trimethylamine and putrescine are the dominant biogenic amines during the cold storage process. Other freshness indicates including sensory evaluation, hardness, pH and total volatile basic nitrogen (TVB-N) also show good consistency with volatile biogenic amines. The developed method is a rapid, simple, and sensitive method for the determination of volatile biogenic amines in grass carp.

Determination of seafood spoilage by digital colorimetry of indicator test systems

A simple and affordable colorimetric procedure for determination of the seafood spoilage (e.g., shrimp, squid, catfish and herring) using a smartphone and chemometric analysis is considered. The proposed colorimetric sensor consists of 12 zones, i.e., disks of cellulose paper 4 mm in diameter impregnated with acid-base indicators with a color change in the pH range of 3 – 8.8. Spoiling of the seafood is accompanied with a release of volatile biogenic amines that change the color of the indicator zones. A device and a method for measuring the colorimetric parameters of a test system using a smartphone as a recording device equipped with a specialized RGBer product are described. Processing of the data array (the sum of the R, G, and B channel values for each indicator, or the R, G, and B values for individual indicators) was performed using the XLSTAT software. Patterns of the degradation of food products identified in the study made it possible to propose a method for assessing the quality of seafood in real time. The optimal time regime of heat treatment of the sample was determined, which is necessary for the isolation of biogenic amines and the formation of an analytical signal. The parameters for identification of the seafood spoilage are the values of the main component F1 (or the position of the images on the canonical function projection graph) after evaluating the colorimetric data using the principal component method. The results obtained with a colorimetric sensor match the data for determination of the total microbial number of the analyzed products. The considered method for assessing spoilage of the seafood is distinguished by the simplicity of hardware design, the availability of the materials and software resources used, the rapidity of the procedure, and the mobility of the means for recording the analytical signal.

Biphenyl-based AIE-active turn-on fluorescent probes for simultaneous sensing of biothiols and amine vapors and visual real-time monitoring of seafood spoilage

Abnormal level of biothiols content in living organisms and volatile vapor amines could cause severe injury to human health, development of convenient and portable detecting devices for the biothiols and amines recognition is bound to scientific significance as well as practical application. Up to now, mainly confined by aggregation caused quenching (ACQ) effect, the potential application of traditional fluorescent sensing were extremely restricted. In this contribution, two biphenyl-based “turn-on” type fluorescent probes FCH-NBSC and FCH-AC were designed and constructed for biothiols and vapor amines quantitative detection respectively, which were consisted of a common fluorophore FCH–OH with AIE properties and two sensitive recognition segments nitrobenzene sulfonyl chloride (NBSC) and acetyl (AC). Date from experiments demonstrated that probe FCH-NBSC and FCH-AC exhibited excellent linearity and low detection limits for detection of biothiols (Cys, 0.228 μM, GSH, 0.212 μM, Hcy, 0.315 μM, vapor amine, 7.6 ppm), respectively. Sensing mechanism demonstrated that this fluorescent characteristics variation could be ascribed to biothiols and vapor amines caused cleavage of NBSC segment of FCH-NBSC and AC group of FCH-AC respectively to form a common ESIPT compound FCH–OH, which opened aggregation induced emission (AIE) property promoted by intra/intermolecular H-bonds. Furthermore, FCH-NBSC can successfully achieve rapid biothiols recognition inside biological cells via difference in fluorescent signals due to its low toxicity and high sensitivity. Meanwhile, probe FCH-AC have been applied in visual real-time monitoring of seafood spoilage field due to its unique recognition effect for amine vapor.

A ratiometric fluorescence amine sensor based on carbon quantum dot-loaded electrospun polyvinylidene fluoride film for visual monitoring of food freshness

A ratiometric fluorescence sensor based on dual-emission carbon quantum dots (CQD) was developed to real time monitor food spoilage. Two hydrophobic electrospun fluorescent films were developed using polyvinylidene fluoride (PVDF) as the film-forming polymer in combination with CQD as the fluorescent probe. The CQD/PVDF film and CQD@PVDF film enabled the analysis of TMA with limits of detection (LODs) of 1.04 μM and 2.1 μM, respectively, and they exhibited excellent stability at 4 °C. By these virtues, the CQD@PVDF film exhibited visible fluorescence color changes from yellow green to blue by real time and nondestructively sensing volatile amines generated from beef, pork and shrimp in a packaging system with high humidity. This strategy provided a simple but useful, non-destructive, robust, and platform to real time monitor food spoilage for intelligent food packaging.

Multi-Stimuli-Responsive Chromic Behaviors of an All-in-One Viologen-Based Cd(II) Complex.

A one-dimensional Cd(II) chain coordination polymer constructed by an electron-deficient viologen-anchored carboxylate ligand was successfully synthesized. Owing to the favorable stimuli-chromic properties of viologen, the title compound shows reversible photochromism, thermochromism, electrochromism, and naked-eye-detectable differentiable vapochromic response to different volatile amines. The chromic behaviors of it are ascribed to the formation of viologen radicals triggered by external stimuli. And the differentiated response to volatile amines is attributed to the size effect of the amines as well as the steric hindrance effect of forming α/β Cv-H···Namines interactions of the viologen unit to further affect the occurrence of electron transfer. Such an all-in-one crystalline material might have more practical applications in photoelectric, erasable inkless printing, light printing, and volatile amine detection fields.

Simultaneously realizing enhancement of sensitivity for freshness monitoring and multinomial properties of carrageenan/konjac glucomannan/blueberry anthocyanin-based intelligent film by diatomite

Here, highly sensitive blueberry anthocyanin (BBA)-induced intelligent indicating films were fabricated by incorporating a novel composite ingredient, diatomite (DA), into a matrix of konjac glucomannan (KGM), carrageenan (CAR) and BBA. We systematically investigated the effects of introducing DA and BBA on the structure, physical properties, colorimetric response, and practical application of the KGM/CAR film. Our findings revealed that the DA particles and BBA were well-distributed in the KGM/CAR matrix through hydrogen bonding interactions. This distribution significantly improved tensile strength, surface hydrophobicity, thermal stability, and barrier properties of the KGM/CAR film. Notably, the KGM/CAR-based intelligent film loaded with 6 % DA exhibited the most optimal properties. Furthermore, DA exhibited a hierarchical porous structure, enabling the KGM/CAR film to detect volatile amines with heightened sensitivity. When applied to monitor shrimp spoilage in transparent plastic packaging, the color of the composite film underwent remarkable changes from bright pink to bluish violet. These color changes correlated well with the total volatile basic nitrogen (TVB-N) and pH changes in the shrimp, as determined by standard laboratory procedures. Our work presents a promising approach to the development of high-performance and intelligent food packaging materials. These materials hold great potential for practical applications in the field of food packaging.

On-site colorimetric food spoilage monitoring with smartphone embedded machine learning

Real-time and on-site food spoilage monitoring is still a challenging issue to prevent food poisoning. At the onset of food spoilage, microbial and enzymatic activities lead to the formation of volatile amines. Monitoring of these amines with conventional methods requires sophisticated, costly, labor-intensive, and time consuming analysis. Here, anthocyanins rich red cabbage extract (ARCE) based colorimetric sensing system was developed with the incorporation of embedded machine learning in a smartphone application for real-time food spoilage monitoring. FG-UV-CD100 films were first fabricated by crosslinking ARCE-doped fish gelatin (FG) with carbon dots (CDs) under UV light. The color change of FG-UV-CD100 films with varying ammonia vapor concentrations was captured in different light sources with smartphones of various brands, and a comprehensive dataset was created to train machine learning (ML) classifiers to be robust and adaptable to ambient conditions, resulting in 98.8% classification accuracy. Meanwhile, the ML classifier was embedded into our Android application, SmartFood++, enabling analysis in about 0.1 s without internet access, unlike its counterpart using cloud operation via internet. The proposed system was also tested on a real fish sample with 99.6% accuracy, demonstrating that it has a great advantage as a potent tool for on-site real-time monitoring of food spoilage by non-specialized personnel.

Comparison of microbial communities and volatile profiles of wines made from mulberry and grape.

In this study, three kinds of wines separately made from mulberry (MW), grape (GW), or mulberry/grape (MGW) were developed and their enological parameters, sensory scores, volatile components, and microbiota were investigated and compared. Contrary to the order of residual sugar and acidity of the three kinds of wines, the order of alcohol content from high to low is GW, MW, and MGW. A total of 60 volatile components (VCs), including esters (17), alcohols (12), acids (6), aldehydes (7), ketones (3), alkenes (3), amines (3), alkanes (4), pyrazines (2), benzene (1), sulfide (1), and thiazole (1), were identified by gas chromatography-ion mobility spectrometer (GC-IMS). The fingerprint of VCs and principal component analysis revealed that the volatile profiles of MGW and GW were more similar in comparison to that of MW and were significantly correlated with the mass ratio of mulberry to grape. Lactobacillus, Weissella, Pantoea, Leuconostoc, Lactococcus, Paenibacillus, Pediococcus, and Saccharomyces were identified as the main microflora at the genus level shared by the MW, MGW, and GW, suggesting that the heterolactic bacteria may contribute more to the high content of volatile acids in MW and MGW. The heatmap of core microbiota and main VCs of MW, MGW, and GW suggested the complicated and significant correlation between them. The above data implied that the volatile profiles were more closely related to the raw materials of winemaking and markedly affected by the fermentation microorganisms. This study provides references for evaluation and characterization of MGW and MW and improvement of MGW and MW winemaking process. KEY POINTS: • Fruit wine enological parameters, volatile profile, and microbiota were compared. • Sixty volatile compounds were identified by GC-IMS in three types of fruit wines. • Winemaking materials and microbiota affect volatile profiles of the fruit wines.