Microbial contribution to 14 biogenic amines accumulation in refrigerated raw and deep-fried hairtails (Trichiurus lepturus).

Biogenic amines (BAs) produced by microbial decarboxylation of amino acids are crucial toxic nitrogenous compounds in fish. An optimized ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method with simple pretreatment was established to detect 14 BAs in both raw (control check, CK) and deep-fried (DF) hairtails. This method exhibited a good linear relationship with average recoveries of 73.3-120.0 % and relative standard deviations of 2.5-10.0 %, respectively. The total BAs in CK and DF hairtails decreased sharply to 338.2 and 25.3 mg/kg on the 9th day, respectively. Four BAs, including cadaverine (CAD), histamine (HIS), tyramine (TYR), and putrescine (PUT) accounted for 92.5-99.9 % of total BAs were selected as the dominant BAs. Bacterial analysis showed that the abundance of DF was relatively low. Further correlation analysis proved that Vibrio had a significant (p < 0.05) positive correlation with total BAs and could be the main BA-producing bacterium in DF hairtail. This work provides new evidence of the accumulation of BAs in refrigerated hairtail.

High-throughput detection and dietary exposure risk assessment of 44 mycotoxins in Mango, Litchi, Longan, and their products in South China.

Mycotoxins exposure from food can trigger serious health hazards. This study aimed to establish an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous detection of 44 mycotoxins in fruits and their products, followed by dietary exposure risk assessment. The optimized UPLC-MS/MS method exhibited a good linear relationship with correlation coefficients ≥ 0.99041. The limits of detection (LOD) and the limits of quantification (LOQ) were within the range of 0.003 âˆ¼ 0.700 µg/kg and 0.01 âˆ¼ 2.00 µg/kg, respectively. The three fruits and their corresponding value-added products, with a total sampling size of 42, were subjected to analysis and detected with mycotoxins. Further dietary exposure risk assessment revealed that the hazard quotient (HQ) and hazard index (HI) of mycotoxins were 1.213 âˆ¼ 60.032 % and 5.573 âˆ¼ 93.750 %, indicating a low risk for Chinese consumers. However, we still need be cautious about 15-acetyl-deoxynivalenol (15-ADON), as it had 78.6 % occurrence among all samples. This work provides an accurate analysis strategy for 44 mycotoxins and contributes to mycotoxins supervision.

A Chemiluminescence Enzyme Immunoassay Based on Biotinylated Nanobody and Streptavidin Amplification for Diazinon Sensitive Quantification.

The advantages of genetic modification and preferable physicochemical qualities make nanobody (Nb) easy to develop a sensitive and stable immunosensor platform. Herein, an indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) based on biotinylated Nb was established for the quantification of diazinon (DAZ). The anti-DAZ Nb, named Nb-EQ1, with good sensitivity and specificity, was obtained from an immunized library via a phage display technique, where the molecular docking results indicated that the hydrogen bond and hydrophobic interactions between DAZ and complementarity-determining region 3 and framework region 2 in Nb-EQ1 played a critical role in the Nb-DAZ affinity processes. Subsequently, the Nb-EQ1 was further biotinylated to generate a bi-functional Nb-biotin, and then an ic-CLEIA was developed for DAZ determination via signal amplification of the biotin-streptavidin platform. The results showed that the proposed method based on Nb-biotin had a high specificity and sensitivity to DAZ, with a relative broader linear range of 0.12-25.96 ng/mL. After being 2-folds dilution of the vegetable samples matrix, the average recoveries were 85.7-113.9% with a coefficient of variation of 4.2-19.2%. Moreover, the results for the analysis of real samples by the developed ic-CLEIA correlated well with that obtained by reference method GC-MS (R2 ≥ 0.97). In summary, the ic-CLEIA based on biotinylated Nb-EQ1 and streptavidin recognition demonstrated itself to be a convenient tool for the quantification of DAZ in vegetables.

Preparation and evaluation of a novel chlorine dioxide preservative based on citric acid grafted carboxymethyl chitosan.

Instrument-free chlorine dioxide (ClO2) preservative for fruit and vegetable has gained great attention due to its convenience and safety. In this study, a series of carboxymethyl chitosan (CMC) with citric acid (CA) substituents were synthesized, characterized, and further used to prepare a novel ClO2 slow-releasing preservative for longan. UV-Vis and FT-IR spectra revealed that CMC-CA#1-3 were successfully prepared. Further potentiometric titration showed that the mass ratios of CA grafted in CMC-CA#1-3 were 0.18:1, 0.42:1, and 0.42:1, respectively. The composition and concentration of ClO2 slow-releasing preservative were optimized, and the best formulation was as follows: NaClO2:CMC-CA#2:Na2SO4:starch = 3:2:1:1. The maximum ClO2 release time of this preservative reached >240 h at 5-25 °C, and the maximum release rate always occurred at 12-36 h. Longan treated with 0.15-1.2 g ClO2 preservative had significantly (p < 0.05) higher L* and a* values but lower respiration rate and total microbial colony counts than the CK group (0 g ClO2 preservative). After 17 days of storage, longan treated with 0.3 g ClO2 preservative had the highest L* value of 47.47 and lowest respiration rate of 34.42 mg·kg-1·h-1, showing the best pericarp color and pulp quality. This study provided a safe, effective, and simple solution for longan preservation.

Comparative nutritional and metabolic analysis reveals the taste variations during yellow rambutan fruit maturation.

The metabolic reasons for rambutan taste variations during maturity are unknown. Here, we obtained a unique rambutan cultivar Baoyan No.2 (BY2) with a strong yellow pericarp and excellent taste, the sugar-acid ratios of which ranged from 21.7 to 94.5 during maturation. Widely targeted metabolomics analysis was performed to reveal the metabolic reasons behind these taste variations. The results showed that 51 metabolites were identified as common different metabolites (DMs), including 16 lipids, 12 amino acids and others. Among them, the abundance level of 3,4-digalloylshikimic acid exhibited a positive correlation with the titratable acids (R2 = 0.9996) and a negative correlation with the sugar-acid ratio (R2 = 0.9999). Therefore, it could be a taste biomarker of BY2 rambutan. Moreover, all DMs were enriched in "galactose metabolism", "fructose and mannose metabolism" and "biosynthesis of amino acids" pathways, which predominantly accounted for the taste variation. Our findings provided new metabolic evidence for the taste variation of rambutan.

Metabolic Profiling and Potential Taste Biomarkers of Two Rambutans during Maturation.

The metabolite-caused taste variation during rambutan maturation is unknown due to a lack of systematic investigation of all components. In this study, three growing stages, including unripe (S1), half-ripe (S2), and full-ripe (S3) BY2 and BY7 rambutans were compared and profiled by UPLC-MS/MS-based widely targeted metabolomics analysis. We demonstrated that the sugar-acid ratios of two rambutans were greatly improved between the S2 and S3 stages. A total of 821 metabolites were identified, including 232, 205, 204, and 12 differential metabolites (DMs) in BY2-S1 vs. BY2-S2, BY2-S2 vs. BY2-S3, BY7-S1 vs. BY7-S2, and BY7-S2 vs. BY7-S3, respectively. A correlation analysis showed that gamma-aminobutyric acid (GABA) could be the sugar-acid ratio biomarker of BY2 rambutan. Methionine (Met), alanine (Ala), and S-methyl-L-cysteine (SMC) could be total amino acid biomarkers of BY2 and BY7 rambutans. In addition, UPLC-MS/MS-based quantitative verification of the above biomarkers exhibited the same variations as metabolomics analysis. This study not only provides useful nutritive information on rambutans but also valuable metabolic data for rambutan breeding strategies.

Risk Assessment of Triflumezopyrim and Imidacloprid in Rice through an Evaluation of Residual Data.

Triflumezopyrim, a novel mesoionic insecticide used to control planthoppers, is a potential substitute for imidacloprid. In this study, triflumezopyrim and imidacloprid residues in rice were determined using a quick, easy, cheap, effective, rugged, and safe procedure combined with ultra-high-performance liquid chromatography-tandem mass spectrometry. The limit of quantification of both triflumezopyrim and imidacloprid was 0.01 mg kg-1, and the average recovery values were 94-104% and 91-106%, with relative standard deviations (RSDs) of 1.1-1.4% and 2.1-3.4% (n = 5), respectively. The consumer protection level was assessed by calculating the theoretical maximum daily intake using the reported maximum residue limits of triflumezopyrim and imidacloprid. The established method was successfully applied to 200 commercial rice samples collected from four provinces in China, and their potential public health risks were assessed using triflumezopyrim and imidacloprid residues. The risk associated with triflumezopyrim and imidacloprid dietary intake was assessed by calculating the national estimated short-term intake and the acute reference dose percentage (%ARfD). The results show that the theoretical maximum daily intake (NEDI) values of triflumezopyrim and imidacloprid in different age and gender groups were 0.219-0.543 and 0.377-0.935 µg kg-1 d-1 bw, and the risk quotient (RQ) values were 0.188-0.467% and 0.365-0.906%, respectively. The acute reference dose (%ARfD) of triflumezopyrim and imidaclopridin ranged from 0.615 to 0.998% and from 0.481 to 0.780%, respectively.

Detection and Degradation Characterization of 16 Quinolones in Soybean Sprouts by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry.

Recently, there have been increasing safety concerns about the illegal abuse of quinolone in soybean sprouts. This study aimed to establish an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous detection of 16 quinolones (QNs) in soybean sprouts, and then reveal their degradation characteristics. The samples were extracted with acetonitrile (with 1% formic acid), purified by a C18 adsorbent, and separated by an ACQUITY UPLC BEH C18 (1.7 µm, 2.1 mm × 100 mm) column. The internal standard method was applied for quantitative determination. The results demonstrated that the quantification linear range for 16 QNs was between 2.0 ng/mL and 50.0 ng/mL. The detection limits were between 0.5 µg/kg and 4.0 µg/kg, and the quantification limits were between 2.0 µg/kg and 20.0 µg/kg. This method was used to screen for quinolones in 50 batches of market soybean sprouts; the obtained results showed good agreement with those of the standard method. It was found that QNs possessed longer degradation half-life (T1/2) in the storage stage of soybean sprouts, while they degraded to some extent during the germination stage via active enzyme action. In particular, ciprofloxacin was the most stable QNs with a T1/2 of 70.71 d during the storage stage of soybean sprouts. This work not only offers an accurate and efficient QNs residual analysis strategy but also provides a reference for the supervision and management of QNs in foods.

Comparative Metabolomics Analysis Reveals the Taste Variations among Three Selected Wampee Cultivars.

Sugars and acids of wampee predominantly influence consumer taste preference and its commercial value. The molecular basis of taste variations is currently unknown due to the lack of a large-scale investigation of metabolites in wampee. Here, three tastes cultivars, including YF1 (sweet), YF2 (sweet-sour) and YF3 (sour) wampees with sugar-acid ratios ranging from 1.74 to 26.32, were selected. Then, UPLC-MS/MS based widely targeted metabolome analysis was performed to uncover the molecular mechanism underlying these taste variations, followed by the analysis of KEGG pathways. Results showed that 449, 470, 147 metabolites differed between YF1 vs YF2, YF1 vs YF3, and YF2 vs YF3. Fifty of them were screened as common differential metabolites (DMs) by Venn diagram, including 9 phenolic acids. Among them, the abundance level of methyl 3-O-methyl gallate (M3MG) showed a positive correlation with the titratable acids (R2 = 0.9009) and negative correlation with sugar-acid ratio (R2 = 0.9802) in three cultivars. Therefore, M3MG could be a taste biomarker for wampees. KEGG pathway enrichment analysis also verified that M3MG played a crucial role in the "biosynthesis of amino acids" pathway. These results above provide important insights into the taste-forming mechanism of wampee and will be beneficial for superior eating quality wampee breeding.

Identification and verification of key taste components in wampee using widely targeted metabolomics.

Due to the lack of comprehensive evaluation of all metabolites in wampee, the metabolic reasons for taste differences are unclear. Here, two local varieties YF1 (sweet taste) and YF2 (sweet-sour taste), were selected for quality analysis, followed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) based widely targeted metabolomic analysis. YF1 and YF2 were clearly separated by principal component analysis (PCA) and cluster analysis, and 449 metabolites were different between the cultivars, including 29 carbohydrates and 29 organic acids. Among them, d-galactose, d-mannose, and d-fructose 6-phosphate contributed mainly to the sweet taste of the YF1 wampee. l-citramalic acid, 2-hydroxyglutaric acid, and 3-methylmalic acid were the dominant organic acids in YF2 wampee, and therefore, contributed primarily to the sweet-sour taste. The differential metabolites were significantly enriched in the "ascorbate and aldarate metabolism" and "C5-branched dibasic acid metabolism" pathways. Ascorbate played a crucial role in the regulation of sugars and organic acids through those pathways. In addition, high-performance liquid chromatography (HPLC) based quantitative verification exhibited the same specific cultivar variations.

Analysis on quality differences associated with metabolomics of rambutan during different temperature storage.

This study aimed to understand how temperatures differentially impact the crucial quality indices and metabolites in rambutan during storage. Rambutan browned quickly at room temperature from 0 d (control). After ten days at 5 â„ƒ, browning index and lightness were 4.2% and 147.5%, compared with rambutan stored at 1 â„ƒ, which was the best quality achieved. An UPLC-MS/MS was performed to uncover the metabolism underlying those quality differences, followed by the analysis of KEGG pathways. Results showed that 276 differentially expressed metabolites (DEMs) screened were enriched in 18 KEGG pathways. The pathways related to carbohydrates, aliphatic metabolites, and organic acids were highly active in rambutan stored at room temperature, whereas the pathways related to amino acids biosynthesis and nucleotides were highly active in rambutan stored at 1 â„ƒ, 5 â„ƒ. These findings indicated that increased scopoline was associated with serious browning at room temperature. L-leucine and L-isoleucine both increased in response to low temperature and reduced browning. Glutathione and ascorbate decreased to 4.89% and 4.36%, compared with 0 d (CK) in rambutan with severe browning stored at 1 â„ƒ for ten days. However, no significant changes in those two metabolites were observed in rambutan stored at optimal 5 °C for ten days. Thus glutathione and ascorbate could be used as potential indicators of browning degree. Our study provided a metabolic insight into the role of temperature on rambutan quality and browning.