Biotransformation of carbendazim in cowpea pickling process.

Carbendazim, a systemic fungicide, is one of the most commonly detected pesticides in cowpeas. Pickled cowpea is a fermented vegetable product with unique flavor favored in China. The dissipation and degradation of carbendazim were investigated in the pickled process. The degradation rate constant of carbendazim in pickled cowpeas was 0.9945 and the half-life of the carbendazim was 14.06 ± 0.82 d. Seven transformation products (TPs) were identified in the pickled process. Furthermore, the toxicity of some TPs show more harmful to three aquatic organisms (TP134) and rats (all the identified TPs) than carbendazim. And most of the TPs posed more development toxicity and mutagenicity than carbendazim. 4 out of 7 TPs were discovered in the real pickled cowpea samples. These results shed light on the degradation and biotransformation of the carbendazim in the pickled process, to better understand the potential health risk of pickled food and evaluate the environmental pollution.

Occurrence and source analysis of polychlorinated naphthalenes in raw cow milk.

The potential contamination of food items with polychlorinated naphthalenes (PCNs) has attracted increasing attention because of their toxicity, persistence and bioaccumulative characteristics. Humans are exposed to PCNs primarily through consuming animal-derived foodstuffs. However, the pathways by which PCNs can enter the food supplying chain are poorly understood. In this study, Σ75PCNs were determined in raw cow milk (n = 82) collected from three different regions that varied in the intensity of PCNs emission sources in North China, using high-resolution gas chromatography/high-resolution mass spectrometry method. Higher PCN concentrations (214-2050 pg/g lw) were found in raw cow milk from dairy cow farms located in the region with relatively higher intensity of emission sources. Less chlorinated congeners were dominant in all raw cow milk samples. PCNs in cow milk might result from industrial fly ash emissions that contaminate animal feed through atmospheric deposition. Risks posed to humans through consuming PCNs in cow milk were low.

Polychlorinated naphthalenes in farmed Chinese mitten crabs in China: Concentration, distribution and source analysis.

Polychlorinated naphthalenes (PCNs) are both highly toxic and bioaccumulative environmental contaminates. Dietary intake is the primary pathway for human exposure to PCNs, and PCN concentrations in aquatic foodstuffs are relatively high. Chinese mitten crab (Eriocheir sinensis) is one kind of popular aquatic foodstuffs in Asian countries. Farmed crabs could exposure to PCNs both through feed and environment. However, information on the occurrence of PCNs in farmed crabs is scarce. The present study investigated 75 PCN congeners in farmed Chinese mitten crabs, crab compound feed and sediments collected from Anhui Province and Shanghai in China. The total PCN concentrations in farmed Chinese mitten crabs from Anhui Province and Shanghai were 11.2-42.2 and 5.46-43.8 pg/g wet weight (ww), respectively. The PCN homologue profiles in crabs from both areas were similar, and both were dominated by di-CNs and penta-CNs. In contrast, lower chlorinated PCNs (di-CNs, tri-CNs and tetra-CNs) were the most common homologues in specimens of crab compound feed and sediment samples, indicating that selective bioaccumulation and metabolism of PCNs might occur in farmed crabs. No regional differences were found in the PCN congener profiles of farmed crabs, feed and sediment samples taken from Anhui Province and Shanghai. An assessment found no significant health risk associated with Chinese exposure to PCNs through farmed Chinese mitten crab consumption.

Reevaluation on accumulation and depletion of dioxin-like compounds in eggs of laying hens: Quantification on dietary risk from feed to egg.

Updated assessment on transfer of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) from feed to food is essential for understanding human exposure risk. A controlled feeding experiment was conducted for laying hens to reevaluate the transfer characteristics of dioxin-like compounds from feed to egg. Two fortified diets (1.17 and 5.13 pg TEQ g-1 dry weight), made by blending with fly ash, were fed to laying hens for 14 days, followed by 28-days depletion. Levels of ∑TEQPCDD/Fs+DL-PCBs in eggs rapidly increased once exposure started, reaching at 1.98 and 6.86 pg TEQ g-1 lw at the end of exposure for low- and high-exposure groups, respectively, and dropped to under the European legislation (maximum levels: 5.0 pg TEQ g-1 lw) after 28-days depletion. The quantitative depletions showed that the half-lives (T1/2) of ∑TEQPCDD/Fs in eggs were 23 and 14 days for low- and high-exposure groups, respectively. The depletion and accumulation rates of PCDD/Fs were in the range of 0.026-0.151 and 0.005-0.016 day-1, respectively, representing that the T1/2 of PCDD/Fs in eggs ranged from 5 to 27 days. The depletion kinetics of DL-PCBs was not significant in egg. The hens with higher laying rates exhibited shorter T1/2 of PCDD/Fs, implying that increasing laying rate could expedite the depletion of PCDD/Fs in egg. The T1/2 of PCDD/Fs in egg were negatively correlated with the chlorine number, indicating that lower chlorinated congeners tended to be retained in the egg. Transfer rates of PCDD/Fs were in the range of 4-19%, which were lower than the previous results. These results were attributed to short exposure time and low bioavailability of PCDD/Fs in fly ash. Estimations of dietary intake highlighted the dietary risk of PCDD/Fs from feed to egg, which would pose limited adverse effects on human health.

Concentrations and sources of short- and medium-chain chlorinated paraffins in farmed Chinese mitten crabs in China.

Aquatic foods are important sources of chlorinated paraffins (CPs) to humans. Farmed crabs are bottom-dwelling aquatic animals, and can accumulate CPs through food and aquatic environment. However, limited information is available on CPs concentrations in and sources to farmed crabs. In this study, short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) concentrations in 59 samples from the farmed crab food web (crab, crab feed, and aquaculture environment) were determined. The samples were from 17 crab farms in Anhui Province, Jiangxi Province, and Shanghai, in China. The SCCPs and MCCPs concentrations in the crab samples were 82-1760 and not detected-680 ng/g lipid weight, respectively. The dominant SCCPs and MCCPs in the crab samples were C10Cl6-7 and C14Cl7-8, respectively. The SCCPs concentrations in the crab food web samples were higher than the MCCPs concentrations. SCCPs contamination of the crab food web samples was not directly related to CPs product use. The main factors affecting SCCPs concentrations in the crab samples were different for different crab farms. Crab feed and the aquaculture environment could be sources of SCCPs to farmed crabs. No marked health risks are posed to humans through consuming CPs in Chinese mitten crabs farmed in China.

Determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin based on SERS substrates composited of Au nanoparticles supported on twice-oxidized graphene oxide.

A surface-enhanced Raman spectroscopy (SERS) substrate consisting of Au nanoparticles supported on twice-oxidized graphene oxide (ro-GO) for the determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was prepared. The Raman shift at △v = 779, 993, and 1203 cm-1 was collected on the excitation condition of λ = 785 nm for the qualitative identification of 2,3,7,8-TCDD in milk. The peak at △v = 1203 cm-1 was selected as the characteristic peak for quantitation. The quantitation calculation was realized in the concentration range 10 to 100 ng mL-1 with a limit of detection of 3.24 ng mL-1 in milk samples. The average recoveries of 2,3,7,8-TCDD in milk were 60.6-68.6% with relative standard deviations less than 6.4%. The long-term stability of the substrates was approximately 180 days at 4 °C. Further, the SERS method for the determination of 2,3,7,8-TCDD in milk samples based on the optimized hybrid SERS substrate and corresponding pre-treatment procedure is proposed. Graphical abstract Schematic representation of surface-enhanced Raman spectroscopy (SERS) determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in milk samples by Au nanoparticles supported on twice-oxidized graphene oxide (ro-GO/AuNP) as a substrate.

Short- and medium-chain chlorinated paraffins in plastic animal feed packaging and factors affect their migration into animal feed.

Chlorinated paraffins (CPs) are used as plasticizers and flame retardants in plastics. Plastic packaging containing CPs is widely used for storage of animal feed, which can become contaminated by CPs that migrate into the feed. In the present study, 31 commercial animal feed packaging samples made of polypropylene (PP) or polyethylene (PE) were collected from animal feed manufacturers in China. The mean concentrations of short-chain chlorinated paraffins (SCCPs) in the PP and PE samples were 60.0 and 54.5 µg/g, respectively. The medium-chain chlorinated paraffin (MCCP) mean concentrations in the PP and PE samples were 62.7 and 9.23 µg/g, respectively. The carbon congener group profiles of SCCPs and MCCPs in the samples were different. The dominant SCCP and MCCP chlorine congener groups in all the samples were Cl6-7 and Cl6-8, respectively. Time and temperature influenced the migration of CPs from packaging into animal feed. As the time or temperature increased, the CP concentrations in the animal feed increased but the congener group profiles of the SCCPs and MCCPs in the animal feed did not change. To reduce contamination of animal feed by CPs, it is necessary to restrict the use of CPs in animal feed packaging.

Aroma Compounds in Chicken Broths of Beijing Youji and Commercial Broilers.

The unique flavor of Beijing Youji (BJY) chicken broth compared with that of commercial broilers (CB) was investigated by solvent-assisted flavor evaporation combined with AEDA/GC-O (aroma extract dilution analysis of gas chromatography-olfactometry), quantitation, and aroma recombination. A total of 71 odorants with almost the same major odorants (≥10 ng/g broth) were found by GC-O in both BJY and CB broths. However, BJY broth had thirty-two more extra odorants than CB broth, indicating the rich fragrance of the former. Aroma recombination and omission experiments demonstrated that 21 versus 17 odorants (with OAV ≥ 1) contributed significantly to BJY and CB broth aromas, respectively. Those key odorants mainly included sulfur-containing compounds and aliphatic aldehydes, such as 2-methyl-3-furanthiol, 3-(methylthio)propanal, ( E, E)-2,4-decadienal, etc. Furthermore, composition analysis of the meat suggested that the better flavor, with rather more odorants, of BJY broth is probably due to higher contents of polyunsaturated fatty acids and water-soluble flavor precursor, including ribose, cysteine, thiamine, etc., present in the BJY meat.

Effect of glycine on reaction of cysteine-xylose: Insights on initial Maillard stage intermediates to develop meat flavor.

The meat-like reactions of l-cysteine and d-(+)-xylose with or without glycine were investigated. LC-MS was used to quantitatively determine the initial stage intermediates including 2-threityl-thiazolidine-4-carboxylic acid, Cys-Amadori, and Gly-Amadori in the reaction mixtures. The results showed that the addition of glycine was only in positive correlation with the browning feature of cyseine-xylose reaction. When excessive glycine was added, a high browning rate would be achieved, but it did not benefit the formation of meaty compounds. For a complex meat-like reaction system containing cysteine, reducing sugars and glycine, to overcome the low rate of reaction, and particularly, to minimize the inhibitive effect of cysteine in the generation of meaty flavors, selection of an appropriate ratio between cysteine and glycine is important in an effort to make amounts of the intermediates of Cys-Amadori and Gly-Amadori approximately equally consist in the reaction mixture.

Roles of different initial Maillard intermediates and pathways in meat flavor formation for cysteine-xylose-glycine model reaction systems.

To explore initial Maillard reaction pathways and mechanisms for maximal formation of meaty flavors in heated cysteine-xylose-glycine systems, model reactions with synthesized initial Maillard intermediates, Gly-Amadori, TTCA (2-threityl-thiazolidine-4-carboxylic acids) and Cys-Amadori, were investigated. Relative relativities were characterized by spectrophotometrically monitoring the development of colorless degradation intermediates and browning reaction products. Aroma compounds formed were determined by solid-phase microextraction combined with GC-MS and GC-olfactometry. Gly-Amadori showed the fastest reaction followed by Cys-Amadori then TTCA. Free glycine accelerated reaction of TTCA, whereas cysteine inhibited that of Gly-Amadori due to association forming relatively stable thiazolidines. Cys-Amadori/Gly had the highest reactivity in development of both meaty flavors and brown products. TTCA/Gly favored yielding meaty flavors, whereas Gly-Amadori/Cys favored generation of brown products. Conclusively, initial formation of TTCA and pathway involving TTCA with glycine were more applicable to efficiently produce processed-meat flavorings in a cysteine-xylose-glycine system.