Nitrite In Foods Research Articles

Electrochemical Detection of Nitrite in Food Based on Poly (3,4-ethylenedioxythiophene) Doped with Fe3O4 Nanoparticles Loaded Carboxylated Nanocrystalline Cellulose

Carboxylated nanocrystalline cellulose (CNCC) was prepared by oxidation degradation of microcrystalline cellulose (MCC) using ammonium peroxydisulfate and modified with Fe3O4 nanoparticles to form Fe3O4-CNCC nanocomposite via simple refluxing process. The Fe3O4-CNCC nanocomposite doped poly(3,4-ethylenedioxythiophene) (PEDOT) was successfully decorated on the glassy carbon electrode (GCE) by electrochemical deposition. The PEDOT/Fe3O4-CNCC modified GCE with enlarged real electrochemical surface area was used to determine nitrite with high selectivity, sensitivity and outstanding reproducibility. Using amperometric current-time (i-t) curve, the proposed sensor provided a wider linear range (0.5-2500 ∆M) and a lower detection limit (0.1 ∆M) towards nitrite compared with the method of differential pulse voltammetry (DPV). This analytical method gave good selectivity in the practical measurement of nitrite in pickles.

Fluorescence quenching capillary analysis for determining trace-level nitrite in food based on the citric acid/ethylenediamine nanodots/nitrite reaction

We found that nitrite after protonation can react with amine radical on citric acid/ethylenediamine carbon nanodots (CA/EDA-CDs) to form nitrosamines, and fluorescence quenching of CA/EDA-CDs occurred during this process. Using the reaction mechanism a fluorescence quenching capillary analysis (FQCA) was developed. After optimized reaction conditions, the following results were obtained: the required concentration of CA/EDA-CDs was 12 mg/L, HCl concentration was 32 mmol/L, and the reaction conducted in room temperature for 20 min. Under optimized conditions, FQCA has a linear response in 20–500 μg/L in which RSD was less 4.5% (n = 11), the detection limit was 6.5 μg/L and the recovery was in 95–105%. The measured results were consistent with the national standard method. FQCA has been used for determining nitrite in foods and nature waters. The capillary in FQCA was used as the container for CA/EDA-CDs/NO2− reaction and NO2− determination, and realized trace-level analysis for micro-volume samples (<10 μL/time).

Isolation of nitrite-degrading strains from Douchi and their application to degrade high nitrite in Jiangshui.

Excessive nitrite in food is potentially harmful to human health because of carcinogenic effects caused by its nitroso-derivatives. Douchi, which widely distributed throughout the country, is a traditional solid fermented soybean food with low nitrite content. In this study, bacteria which can degrade nitrite were isolated from Douchi and identified from their 16S rDNA sequences. Acinetobacter guillouiae, Acinetobacter bereziniae, Bacillus subtilis, Bacillus tequilensis, Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus aryabhattai and Bacillus methylotrophicus were selected. It was shown that all strains were able to degrade nitrite to some extent, including Bacillus subtilis NDS1, which was able to degrade 99.41% of nitrite. The enzyme activities of these strains were determined at 24 and 48 h and were shown to correspond with their nitrite degradation rates. The strains were used to inoculate Jiangshui, a kind of traditional fermented vegetable from northwest China that often has a high nitrite content. Of the strains tested, Bacillus subtilis NDS1, Bacillus tequilensis NDS3, Acinetobacter bereziniae NDS4, Bacillus subtilis NDS6, and Bacillus subtilis NDS12 were able to degrade nitrite in Jiangshui more rapidly, with Acinetobacter bereziniae NDS4 degrading almost all nitrite in 48 h compared with 180 h of control. These results indicate that the selected strains have potential to be used as nitrite-degrading agents in food. © 2018 Society of Chemical Industry.

Electrochemical Biosensor for Nitrite Based on Polyacrylic-Graphene Composite Film with Covalently Immobilized Hemoglobin.

A new biosensor for the analysis of nitrite in food was developed based on hemoglobin (Hb) covalently immobilized on the succinimide functionalized poly(n-butyl acrylate)-graphene [poly(nBA)-rGO] composite film deposited on a carbon-paste screen-printed electrode (SPE). The immobilized Hb on the poly(nBA)-rGO conducting matrix exhibited electrocatalytic ability for the reduction of nitrite with significant enhancement in the reduction peak at −0.6 V versus Ag/AgCl reference electrode. Thus, direct determination of nitrite can be achieved by monitoring the cathodic peak current signal of the proposed polyacrylic-graphene hybrid film-based voltammetric nitrite biosensor. The nitrite biosensor exhibited a reproducible dynamic linear response range from 0.05–5 mg L−1 nitrite and a detection limit of 0.03 mg L−1. No significant interference was observed by potential interfering ions such as Ca2+, Na+, K+, NH4+, Mg2+, and NO3− ions. Analysis of nitrite in both raw and processed edible bird’s nest (EBN) samples demonstrated recovery of close to 100%. The covalent immobilization of Hb on poly(nBA)-rGO composite film has improved the performance of the electrochemical nitrite biosensor in terms of broader detection range, lower detection limit, and prolonged biosensor stability.

Fabrication of gold nanoparticles/l-cysteine functionalized graphene oxide nanocomposites and application for nitrite detection

In this paper, the gold nanoparticles/l-cysteine functionalized graphene oxide (AuNPs/GO-SH) nanocomposites was synthetized with a simple approach for nitrite determination. The prepared nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy, etc. A pair of well-defined redox peaks was founded for AuNPs/GO-SH hybrids with a formal potential of 0.90 V in 0.1 M phosphate buffered solution by cyclic voltammetry. Under optimal conditions, the sensor could detect nitrite as low as 0.25 μM with a wide linear response range from 5 to 1000 μM, high sensitivity and excellent selectivity. The superior results of nitrite determination in pickled radish showed a promising application for determination of nitrite in food.

Electrochemically reduced graphene oxide/gold nanoparticles composite modified screen-printed carbon electrode for effective electrocatalytic analysis of nitrite in foods

Via a single-step electroreduction, the electrochemically reduced graphene oxide/gold nanoparticles (ERGO/AuNPs) composite was prepared on a disposable screen-printed carbon electrode (SPCE) for nitrite sensing. The AuNPs can be well dispersed in the stacked and wrinkled ERGO sheets. The possible mechanism for forming the unique structure of the hybrid composite was proposed. The electrochemical studies showed that AuNPs were efficient electrocatalysts towards the oxidation of nitrite, while the winkled ERGO sheets provide a 3D network scaffold for attachment of AuNPs and absorption of abundant nitrite, and promote the rapid heterogeneous electron transfer. The optimization of electrochemical reaction conditions also has been performed. The optimized electrode exhibited excellent properties for the detection of nitrite, including a low oxidation potential (0.65 V), wide linear range (1–6000 μM), high sensitivity (0.3048 μA μM−1 cm−2), low detection limit of 0.13 μM (S/N = 3), and great selectivity. Moreover, the good accuracy and recovery of ERGO/AuNPs based electrochemical sensor were achieved in the analysis of nitrite in various real food samples.

Carbon quantum dot-basedfluorometric nitrite assay by exploiting the oxidation of iron(II) to iron(III).

The authors describe a simple and economical fluorescence method for the determination of nitrite by utilizing the fact that nitrite possesses strong oxidation in acidic solution and is capable to transform iron(II) into iron(III) ions. The latter quenches the fluorescence of carbon quantum dots (CQDs) based on the fluorescence static and dynamic quenching effect. The optimum reaction conditions and other analytical parameters are investigated to enhance the sensitivity of the method. At the excitation wavelength of 360nm, this probe has a linear response in the 10 to 400μM nitrite concentration range, with a correlation coefficient of R2 = 0.9958 (n = 3) and a detection limit of 0.48μM. This method was successfully applied to the determination of nitrite in three different sausage samples and gave recoveries in the range between 101.8 to 103.0%, demonstrating the accuracy, reliability and potential application of this assay for monitoring nitrite. Graphical Abstract The carbon quantum dot/iron(II) ions system was used for the fluorometric detection of nitrite in food and environmental water. This probe exploits the oxidizing property of nitrite in acidic solution. Iron(II) is oxidized to iron(III) which exerts a strong fluorescence quenching effect.

Evaluation of the Content and Safety of Nitrite Utilisation in Meat Products in Serbia in the Period 2016–2018

Nitrites are inorganic salts widespread in water, fruits, vegetables, meat and meat products. Application of nitrites in the meat industry is necessary for multiple reasons. They suppress development of some microorganisms in food and are a source of nitrogen oxide that is widely involved in physiological functions of metabolism, food intake and energy balance. On the other hand, nitrites in food can produce nitrosamines that increase the risk of cancer. During regular quality control in 2016-2018, 972 samples of meat products were analysed and verified for compliance with regulations concerning nitrite levels, and the average participation of these meat products in daily intake of nitrite was estimated. The amount of nitrites in the examined meat products was within the permitted limits. The daily intake of nitrite in Serbia from meat and meat products was estimated as being from 0.015-0.020 mg kg-1 body weight, which is below the limit values ​​set by EFSA for safe daily intake, i.e. 0.06-0.07 mg kg-1 body weight.

Rapid determination of nitrite in foods in acidic conditions by high-performance liquid chromatography with fluorescence detection.

In this study, a simple, rapid, and sensitive method for the determination of nitrite (NO2 (-) ) in food samples by high-performance liquid chromatography with fluorescence detection in acidic conditions had been developed. The derivatization of the nitrite with 2,3-diaminonaphthalene was performed in acidic conditions to yield the highly fluorescent 2,3-naphthotriazole, which was directly analyzed by high-performance liquid chromatography with fluorescence detection without adjusting the solution to alkaline. The analysis column was reversed-phase C8 column. A constant flow rate of 1.0 mL/min was employed using water/acetonitrile as the mobile phase in isocratic mode (70:30, v/v). Fluorescence was monitored with excitation at 375 nm and emission at 415 nm. The standard calibration curves were linear for nitrite in different matrixes in the concentration range of 0-100 μg/L, and the correlation coefficients ranged from 0.9978 to 0.9998. The limits of detection and quantification were in the ranges of 0.012-0.060 and 0.040-0.20 mg/kg, respectively. The recoveries of nitrite from samples spiked at three different concentrations were 74.0-113.2%, and the relative standard deviations of the recovery results (n = 6) were 1.67-10.8%. The proposed method has good repeatability and is very sensitive and simple. It has been successfully used to determine nitrite in foods.

Simultaneous Determination of Nitrite and Nitrate in Milk Samples by Ion Chromatography Method and Estimation of Dietary Intake

The presence of nitrate and nitrite in foods may be considered hazardous after ingestion in the gastrointestinal tract due to their reaction with naturally occurred secondary amines to form potentially carcinogenic nitrosamines. Due to this fact, a new method was developed in this study for the simultaneous determination of nitrite and nitrate in milk samples using by ion chromatography. Proposed mobile phase composed of sodium hydrogen carbonate and sodium carbonate (1.0 and 3.2 mmol/L) with a flow rate of 0.7 ml/min. The average recoveries for nitrate and nitrite were higher than 86 and 88%, respectively. The limit of detection for nitrate and nitrite were 0.24 and 0.09 mg/L, respectively. The results of 102 real milk samples showed nitrate was found in all of the samples (100%) with a mean of 34 ± 11 mg/L, while nitrite was found in none of the samples. The mean intake of nitrate in all age groups was lower than World Health Organization guideline. The present assessment concludes that the maximum contaminant level was equal to 82.8 mg/L nitrate. This method was fast, sensitive and accurate and is capable of being an alternative method in food control laboratories for investigation of nitrite and nitrate content. This is the first study of the determination and survey of nitrite and nitrate and exposure assessment of the Iranian population to nitrite and nitrate level in milk, which was widely used in infants and adolescents as one of the basic food components.

Electrocatalytic oxidation of nitrite using metal-free nitrogen-doped reduced graphene oxide nanosheets for sensitive detection

Nitrite can become poisonous to animals and human beings as it can lead to generation of carcinogenic N-nitrosamines. Metal-free nitrogen-doped reduced graphene oxide (NrGO) exhibited a good electrocatalytic activity toward oxidation of nitrite with the relatively low oxidation potential of 0.68V (v.s. saturated calomel electrode), thus, a facile electrochemical sensor based on metal-free NrGO was fabricated for sensitive detection of nitrite for the first time. The novel sensor showed a wide linear concentration range from 0.5 to 5000μM and a low detection limit of 0.2μM at the signal-to-noise ratio of 3 with good selectivity, stability, and reproducibility. This fabricated sensor was used for the determination of nitrite in pickled garlic and river water. These results demonstrate that the facile metal-free NrGO-modified electrochemical sensor has promising applications for the determination of nitrite in food and environment.

Utilizing of Ag@AgCl@graphene oxide@Fe3O4 nanocomposite as a magnetic plasmonic nanophotocatalyst in light-initiated H2O2 generation and chemiluminescence detection of nitrite

A simple and sensitive chemiluminescence (CL) procedure was developed for the quantification of nitrite in aqueous solutions. The method is based on light-initiated generation of H2O2 by a magnetic Ag@AgCl@Graphene oxide nanocomposite and its subsequent redox reaction with nitrite ion in acidic medium. During the carbonate-catalyzed decomposition of produced peroxynitrite and energy transferring to uranine, a CL emission was observed at λ=534nm. Several factors affecting the CL intensity were investigated and optimized. Under optimum conditions, the CL intensity was directly proportional to the nitrite concentration in the range of 5‒200ngmL−1. The limit of detection and relative standard deviation (for n=5; at a nitrite concentration of 70ngmL‾1) were 1.15ngmL−1 and 2.57%, respectively. The method was successfully applied to determine nitrite in food stuffs with recoveries in the range of 95.0–103.0% for the spiked samples. The accuracy of the method was evaluated by comparing the results with those obtained by analyzing the samples using a standard method.

Nitrite Reductase and Biosensors Development

Nitrite ions have emerged as one of the major problems in environmental and pollution issuesnowadays. Food products are the major source of these ions to preserve color. However, thereis a maximum permissible limit (MPL) for the use of nitrite in food. A lot of works in theliterature have been carried out on nitrite quantification and most of them are using simple andquick analysis methods. Recently, the advent of biosensor has allowed the fabrication ofsensors for the detection of nitrite. This paper specifically reviews the interest in the usage ofthe nitrite reductase enzyme as a biorecognition element for the application of nitritebiosensors.

Molecular characterization of Lactobacillus plantarum DMDL 9010, a strain with efficient nitrite degradation capacity.

Nitrites commonly found in food, especially in fermented vegetables, are potential carcinogens. Therefore, limiting nitrites in food is critically important for food safety. A Lactobacillus strain (Lactobacillus sp. DMDL 9010) was previously isolated from fermented vegetables by our group, and is not yet fully characterized. A number of phenotypical and genotypical approaches were employed to characterize Lactobacillus sp. DMDL 9010. Its nitrite degradation capacity was compared with four other Lactobacillus strains, including Lactobacillus casei subsp. rhamnosus 719, Lactobacillus delbrueckii subsp. bulgaricu 1.83, Streptococcus thermophilus 1.204, and lactobacillus plantarum 8140, on MRS medium. Compared to these four Lactobacillus strains, Lactobacillus sp. DMDL 9010 had a significantly higher nitrite degradation capacity (P<0.001). Based on 16S rDNA sequencing and sequence comparison, Lactobacillus sp. DMDL 9010 was identified as either Lactobacillus plantarum or Lactobacillus pentosus. To further identify this strain, the flanking regions (922 bp and 806 bp upstream and downstream, respectively) of the L-lactate dehydrogenase 1 (L-ldh1) gene were amplified and sequenced. Lactobacillus sp. DMDL 9010 had 98.92 and 76.98% sequence identity in the upstream region with L. plantarum WCFS1 and L. pentosus IG1, respectively, suggesting that Lactobacillu sp. DMDL 9010 is an L. plantarum strain. It was therefore named L. plantarum DMDL 9010. Our study provides a platform for genetic engineering of L. plantarum DMDL 9010, in order to further improve its nitrite degradation capacity.

Nitrites and nitrates in the human diet: Carcinogens or beneficial hypotensive agents?

Ethnopharmacological relevanceThe presence of nitrite in the human diet was thought to constitute a hazard as secondary nitrosamines are known to cause gastric cancers. Materials and methodsRecent publications on the physiology of serum nitrite have been consulted. Problems: Nitrite is added to some foodstuffs as an antibotulinum agent. Results and DiscussionThe epidemiological evidence that nitrite causes gastric ulcers is weak. On the other hand, evidence that the presence of nitrite in serum lowers blood pressure is strong. This allows us to explain why a Tang dynasty treatment for angina, given in a Dunhuang medical manuscript, can be successful. ConclusionThe presence of nitrite in food is free of danger and a diet high in nitrate is beneficial to the health.

Characterization of nitrite degradation by Lactobacillus casei subsp. rhamnosus LCR 6013.

Nitrites are potential carcinogens. Therefore, limiting nitrites in food is critically important for food safety. The nitrite degradation capacity of Lactobacillus casei subsp. rhamnosus LCR 6013 was investigated in pickle fermentation. After LCR 6013 fermentation for 120 h at 37°C, the nitrite concentration in the fermentation system was significantly lower than that in the control sample without the LCR 6013 strain. The effects of NaCl and Vc on nitrite degradation by LCR 6013 in the De Man, Rogosa and Sharpe (MRS) medium were also investigated. The highest nitrite degradations, 9.29 mg/L and 9.89 mg/L, were observed when NaCl and Vc concentrations were 0.75% and 0.02%, respectively in the MRS medium, which was significantly higher than the control group (p ≤ 0.01). Electron capture/gas chromatography and indophenol blue staining were used to study the nitrite degradation pathway of LCR 6013. The nitrite degradation products contained N2O, but no NH4 +The LCR 6013 strain completely degraded all NaNO2 (50.00 mg/L) after 16 h of fermentation. The enzyme activity of NiR in the periplasmic space was 2.5 times of that in the cytoplasm. Our results demonstrated that L. casei subsp. rhamnosus LCR 6013 can effectively degrade nitrites in both the pickle fermentation system and in MRS medium by NiR. Nitrites are degraded by the LCR 6013 strain, likely via the nitrate respiration pathway (NO2 −>NO−>N2O−>N2), rather than the aammonium formation pathway (dissimilatory nitrate reduction to ammonium, DNRA), because the degradation products contain N2O, but not NH4 +.

Development and Optimization of a SERS Method for On-site Determination of Nitrite in Foods and Water

A rapid, sensitive, and selective detection method of nitrite in foods and water was established by surface-enhanced Raman spectroscopy (SERS) based on the diazo reaction of nitrite with p-nitroaniline and 1-naphthylamine in acidic solution. The azo dye (4-(4-nitrophenyldiazenyl)naphthalene-1-aminium, NNA), which was derived from the diazo reaction, was determined by SERS using citrate-coated silver nanoparticles (AgNPs) as SERS substrates. The concentrations of nitrite in samples were finally calculated from the intensities of SERS signals generated by NNA in the testing solutions. By using the present method combined with a portable miniature Raman spectrometer, on-site determination of nitrite could be performed easily and efficiently. The effects of several experimental parameters on the intensity of SERS signals, such as the volume of AgNP solution and the mixing time of AgNPs and NNA, were investigated. The linear range of the method was 0.1–10.0 mg L−1. The limits of detection (LODs) were 0.01, 0.03, and 0.05 mg L−1 at 720, 1,459, and 1,609 cm−1, respectively. The method was applied to the determination of nitrite in real food and water samples, with recoveries in the range of 86.9–103.4 % and relative standard deviations (RSDs) less than 9.64 %.

Nitrite electrochemical biosensing based on coupled graphene and gold nanoparticles

Biofunctionalized graphene-gold nanoparticle (AuNP) hybrids were prepared using a facile approach of in situ growth, with homogeneous distribution of AuNPs on the graphene nanosheets. Hemoglobin (Hb) was immobilized on the graphene-AuNP composites to fabricate biosensors for determination of nitrite (NO2−). A pair of well-defined redox peaks was observed for Hb immobilized on the graphene-AuNP hybrids with a formal potential (E0′) of −0.314V in 0.1M phosphate buffered saline (0.15M NaCl, pH 7.0). The novel biosensors exhibited many advantages, such as wide linear response range (from 0.05 to 1000µM, R2=0.997), low detection limit (0.01µM, a signal to noise ratio of 3), high sensitivity (0.15μAμM−1cm−2), and excellent selectivity. These constructed biosensors were further used for determination of nitrite in pickled radish. The results obtained were in good agreement with those using spectrophotometry based on the National Food Safety Standard (GB 5009.33-2010), which indicates that these novel and sensitive biosensors have promising application for determination of nitrite in food.

Diazotization-coupling reaction-based selective determination of nitrite in complex samples using shell-isolated nanoparticle-enhanced Raman spectroscopy

A simple, rapid and selective method based on diazotization-coupling reaction for determination of nitrite ion in complex samples using shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was developed. Based on diazotization-coupling reaction, nitrite was transformed into azo dye, which has strong SHINERS activity. Subsequently the concentration of nitrite ion can be determined indirectly from the SHINERS of azo dye. The SHINERS active substrate was composed of gold nanoparticle as core with an ultrathin silica shell having pinhole on the surface. Various factors that influence reaction and SHINERS intensity were investigated. Under the optimal conditions, the linearity was observed in the range of 0.5–6.0mgL−1 with good correlation coefficient (r2>0.9793). The relative standard deviations (RSDs) for five replicate measurements were less than 14.5%. The limit of detections of the method (S/N=3) were 0.07, 0.08 and 0.10mgL−1 at 1137, 1395 and 1432cm−1, respectively, without sample preconcentration. The selectivity of the proposed method was also tested. The performance of SHINERS to determine the concentration of nitrite in food, biological and environmental samples was evaluated. The results indicate that SHINERS shows great potential as a useful analytical tool for trace analysis of nitrite in real samples. This proposed method provides a practical protocol for determination of compounds with weak Raman response, and can be expanded for the indirect detection of iodate ion, phenols and aromatic amines.

Investigation of the nitrate and nitrite contents in milk and milk powder in Taiwan

Cow milk is one of the most important nutrition sources besides breast milk for infants and babies; therefore the detection of nitrate and nitrite in milk is of great importance to the health of infants and babies. Traditional colorimetric method for the determination of the nitrate and nitrite concentrations in food is very tedious. In the present study, 100 samples of milk and milk powder were analyzed by ion chromatography to detect nitrate and nitrite simultaneously without tedious preparation steps. The limit of detection (LOD) for nitrate is 0.33 ppm and the LOD for nitrite 0.07 ppm. The measured nitrate concentration in milk ranged from 0.3 - 417.7 ppm with an average concentration of 92.7 ppm. The nitrite concentration in all milk samples were below the detection limit. The survey information was as the following: (1) the average nitrate concentration of colostrums fortified milk ranged from 14.1 to 136 ppm. (2) the average nitrate concentration of whey fortified milk ranged from 42.6 to 242.8 ppm. (3) the average nitrate concentration of ordinary milk ranged from 57.9 to 157.6 ppm. The dietary intake of nitrate from milk and milk products in Taiwanese adults and children were estimated. All the nitrate exposure levels calculated with the measured results for the different age groups were less than the acceptable daily intake (ADI) of 3.7 mg/ kg body weight per day suggested by WHO. Finally the health effect of nitrate and nitrite in foods was discussed.