Nitrite and nitrosyl compounds in food preservation

A simple and efficient alginate hydrogel combined with surface-enhanced Raman spectroscopy for quantitative analysis of sodium nitrite in meat products

Sodium nitrite is a commonly used preservative and color protectant in the food industry. Conventional analytical methods are highly susceptible to food matrix interference, time-consuming and costly. In this study, the ion cross-linking method was employed to prepare alginate hydrogel substrates, and phenosafranin was chosen as a single-molecule probe to analyze sodium nitrite. Our investigation centered on elucidating the effects of alginate and cross-linking ion concentrations on Raman signal characteristics. The optimal Raman response was observed in the precursor solution with 1% sodium alginate and 0.1 mol L-1 cross-linking ions. The relative standard deviations (RSDs) of the feature peaks from the three substrate batches ranged from 1.22% to 16.30%, attesting the robustness and consistency of the substrates. The signal reduction of the substrates after a four-week storage period remained below 10%, indicating that the substrates had good reproducibility and stability. The limits of detection (LODs) for sodium nitrite in extracts from cured meat, luncheon meat, and sliced ham were determined to range from 3.75 mg kg-1 to 8.11 mg kg-1, with low interference from the food matrix. The support vector machine algorithm was utilized to train and predict the data, which proved to be more accurate (98.6%-99.8% recovery) than the traditional linear regression model (81.9%-112.7% recovery) in predicting the spiked samples. The application of hydrogel-based surface-enhanced Raman spectroscopy (SERS) substrates for nitrite detection in food, combined with machine learning for regression prediction in data processing, collectively augmented the potential of SERS technology in the field of food analysis.

Risk characterization of N-nitrosodimethylamine in pharmaceuticals

Since 2018, N-nitrosodimethylamine (NDMA) has been a reported contaminant in numerous pharmaceutical products. To guide the pharmaceutical industry, FDA identified an acceptable intake (AI) of 96 ng/day NDMA. The approach assumed a linear extrapolation from the Carcinogenic Potency Database (CPDB) harmonic-mean TD50 identified in chronic studies in rats. Although NDMA has been thought to act as a mutagenic carcinogen in experimental animals, it has not been classified as a known human carcinogen by any regulatory agency. Humans are exposed to high daily exogenous and endogenous doses of NDMA. Due to the likelihood of a threshold dose for NDMA-related tumors in animals, we believe that there is ample scientific basis to utilize the threshold-based benchmark dose or point-of-departure (POD) approach when estimating a Permissible Daily Exposure limit (PDE) for NDMA. We estimated that 29,000 ng/kg/day was an appropriate POD for calculating a PDE. Assuming an average bodyweight of 50 kg, we expect that human exposures to NDMA at doses below 5800 ng/day in pharmaceuticals would not result in an increased risk of liver cancer, and that there is little, if any, risk for any other type of cancer, when accounting for the mode-of-action in humans.

Rapid colorimetric assay based on the oxidation of 2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid-diammonium salt for nitrite detection in meat products

This work developed a rapid colorimetric method for nitrite detection in meat products. The detection was based on the reaction of nitrite with 60 mM HCl to produce radicals which further oxidized ABTS (50 µM) to form a water-soluble blue-green product (ABTS•+). The absorbance was measured at a maximum absorption wavelength of 412.5 nm. Parameters such as concentration of HCl, concentration of ABTS and reaction time were evaluated. The absorbance was linearly proportional to the concentration of nitrite (0.1-20 µM) with the limit of detection of 0.34 µM. The proposed method was a time-saving assay since it required only 2 min to complete one measurement. There was no effect of the interference produced by other ions. The assay was robust with 2.5%RSD (n = 50). In meat product samples, high accuracy was observed with the recoveries between 100 ± 2.2% and 105 ± 3.7%. The amount of nitrite in meat products detected by the ABTS method was found in the range of 5.41 - 7.62 mg/kg. The conventional Griess method was applied to determine nitrite in the same meat products. There was no statistically significant difference between the two methods (P = 0.05).

Ascorbate mediates the non-enzymatic reduction of nitrite to nitric oxide

Nitric oxide (NO•) generated by nitric oxide synthases is involved in many physiological and pathophysiological processes. However, non-enzymatic formation of NO• also occurs in vivo. Here we investigated the production of NO• from nitrite, as facilitated by ascorbate, over the pH range of 2.4-7.4. Using a nitric oxide electrode, we observed at low pH a rapid generation of NO• from nitrite and ascorbate that slows with increasing pH. The formation of NO• was confirmed by its reaction with oxyhemoglobin. In the ascorbate/nitrite system a steady-state level of NO• was achieved, suggesting that a futile redox cycle of nitrite-reduction by ascorbate and NO•-oxidation by dioxygen was established. However, at pH-values of around 7 and greater, the direct reduction of nitrite by ascorbate is very slow; thus, this route to the non-enzymatic production of NO• is not likely to be significant process in vivo in environments having a pH around 7.4. The production of nitric oxide by nitrite and ascorbate would be important only in areas of lower pH, e.g. stomach/digestive system, sites of inflammation, and areas of hypoxia such as tumor tissue. In patients receiving very large doses of ascorbate delivered by intravenous infusion, plasma levels of ascorbate on the order of 20 - 30 mM can be achieved. After infusion, levels of nitrate and nitrite in plasma were unchanged. Thus, in blood and tissue that maintain a pH of about 7.4, the reduction of nitrite to nitric oxide by ascorbate appears to be insignificant, even at very large, pharmacological levels of ascorbate.

Seroprevalence of emerging hepatitis E virus in patients with acute hepatitis between 2004 and 2018 in Csongrád County, Hungary

OBJECTIVES

Hepatitis E virus (HEV) has recently become endemic in Europe, however, it is often a remnant neglected by clinicians as the causative agent of acute and chronic hepatitis and is often misdiagnosed as a drug-induced liver injury. The infection rate in European pig farms is estimated to be around 15-20%, therefore, the primary source of HEV infections might be poorly prepared pork meat. As HEV infections may occur more often in clinical practice than previously thought, the present paper aims to analyse the seroprevalence of HEV in patients with acute hepatitis over a period of 14 years in Csongrád County, Hungary.

METHODS

The sera of 4,270 hepatitis patients collected between 2004-2018 were tested for cumulative anti-HEV IgG/IgM. Furthermore, 170 IgM positive sera were tested for the presence of viral RNA by RT-qPCR.

RESULTS

Between 2012-2018, the cumulative seroprevalence has increased 9.18 times, and between 2013-2018, IgM prevalence has increased 12.49 times. Viral RNA was detectable in 12.35% of IgM positive sera.

CONCLUSION

The present paper presents data showing that the seroprevalence of hepatitis E virus has increased markedly over the course of the last decade in Hungary and in other European countries as well. The exact reason behind this phenomenon is yet to be determined. To assess the dynamics and the reason for this increase in prevalence, pan-European, multicentre studies should be conducted.

Highly sensitive capacitance-based nitrite sensing using polydopamine/AuNPs-modified screen-printed carbon electrode

Regulatory bodies play a crucial role in establishing limits for food additives to ensure food quality and safety of food products, as excessive usage poses risks to consumers. In the context of processed animal-based foodstuffs, nitrite is commonly utilized as a means to slow down bacterial degradation. In this study, we have successfully leveraged the redox activity of an electrochemically deposited polydopamine (pDA) film onto gold nanoparticle (AuNP)-modified screen-printed electrodes (SPCE) to develop a sensitive and versatile methodology for the detection of nitrite using redox capacitance spectroscopy. By exploiting the interaction of the AuNPs/pDA electroactive interface with the target nitrite ions, we observed distinct changes in the redox distribution, subsequently leading to modifications in the associated redox capacitance. This alteration enables the successful detection of nitrite, exhibiting a linear response within the concentration range of 10 to 500 μM, with a limit of detection of 1.98 μM (S/N = 3). Furthermore, we applied the developed sensor to analyze nitrite levels in processed meats, yielding good recoveries. These results demonstrate the potential of our approach as a promising method for routine detection of ions.

Non-Targeted Metabolomic Profiling Identifies Metabolites with Potential Antimicrobial Activity from an Anaerobic Bacterium Closely Related to Terrisporobacter Species

This work focused on the metabolomic profiling of the conditioned medium (FS03CM) produced by an anaerobic bacterium closely related to Terrisporobacter spp. to identify potential antimicrobial metabolites. The metabolome of the conditioned medium was profiled by two-channel Chemical Isotope Labelling (CIL) LC-MS. The detected metabolites were identified or matched by conducting a library search using different confidence levels. Forty-eight significantly changed metabolites were identified with high confidence after the growth of isolate FS03 in cooked meat glucose starch (CMGS) medium. Some of the secondary metabolites identified with known antimicrobial activities were 4-hydroxyphenyllactate, 3-hydroxyphenylacetic acid, acetic acid, isobutyric acid, valeric acid, and tryptamine. Our findings revealed the presence of different secondary metabolites with previously reported antimicrobial activities and suggested the capability of producing antimicrobial metabolites by the anaerobic bacterium FS03.

Enhancement of Nitric Oxide Bioavailability by Modulation of Cutaneous Nitric Oxide Stores

The generation of nitric oxide (NO) in the skin plays a critical role in wound healing and the response to several stimuli, such as UV exposure, heat, infection, and inflammation. Furthermore, in the human body, NO is involved in vascular homeostasis and the regulation of blood pressure. Physiologically, a family of enzymes termed nitric oxide synthases (NOS) generates NO. In addition, there are many methods of non-enzymatic/NOS-independent NO generation, e.g., the reduction of NO derivates (NODs) such as nitrite, nitrate, and nitrosylated proteins under certain conditions. The skin is the largest and heaviest human organ and contains a comparatively high concentration of these NODs; therefore, it represents a promising target for many therapeutic strategies for NO-dependent pathological conditions. In this review, we give an overview of how the cutaneous NOD stores can be targeted and modulated, leading to a further accumulation of NO-related compounds and/or the local and systemic release of bioactive NO, and eventually, NO-related physiological effects with a potential therapeutical use for diseases such as hypertension, disturbed microcirculation, impaired wound healing, and skin infections.

Real-Time High-Sensitivity Reaction Monitoring of Important Nitrogen-Cycle Synthons by 15N Hyperpolarized Nuclear Magnetic Resonance

Here, we show how signal amplification by reversible exchange hyperpolarization of a range of ¹⁵N-containing synthons can be used to enable studies of their reactivity by ¹⁵N nuclear magnetic resonance (NO₂^– (28% polarization), ND₃ (3%), PhCH₂NH₂ (5%), NaN₃ (3%), and NO₃^– (0.1%)). A range of iridium-based spin-polarization transfer catalysts are used, which for NO₂^– work optimally as an amino-derived carbene-containing complex with a DMAP-d₂ coligand. We harness long ¹⁵N spin-order lifetimes to probe in situ reactivity out to 3 × T₁. In the case of NO₂^– (T₁ 17.7 s at 9.4 T), we monitor PhNH₂ diazotization in acidic solution. The resulting diazonium salt (¹⁵N-T₁ 38 s) forms within 30 s, and its subsequent reaction with NaN₃ leads to the detection of hyperpolarized PhN₃ (T₁ 192 s) in a second step via the formation of an identified cyclic pentazole intermediate. The role of PhN₃ and NaN₃ in copper-free click chemistry is exemplified for hyperpolarized triazole (T₁ < 10 s) formation when they react with a strained alkyne. We also demonstrate simple routes to hyperpolarized N₂ in addition to showing how utilization of ¹⁵N-polarized PhCH₂NH₂ enables the probing of amidation, sulfonamidation, and imine formation. Hyperpolarized ND₃ is used to probe imine and ND₄⁺ (T₁ 33.6 s) formation. Furthermore, for NO₂^–, we also demonstrate how the ¹⁵N-magnetic resonance imaging monitoring of biphasic catalysis confirms the successful preparation of an aqueous bolus of hyperpolarized ¹⁵NO₂^– in seconds with 8% polarization. Hence, we create a versatile tool to probe organic transformations that has significant relevance for the synthesis of future hyperpolarized pharmaceuticals.

Antimicrobial Impacts of Microbial Metabolites on the Preservation of Fish and Fishery Products: A Review with Current Knowledge

Microbial metabolites have proven effects to inhibit food spoilage microbiota, without any development of antimicrobial resistance. This review provides a recent literature update on the preservative action of metabolites derived from microorganisms on seafood. Fish and fishery products are regarded as a myriad of nutrition, while being highly prone to spoilage. Several proven controversies (antimicrobial resistance and health issues) related to the use of synthetic preservatives have caused an imminent problem. The demand for minimally processed and naturally preserved clean-label fish and fishery products is on rise. Metabolites derived from microorganisms have exhibited diverse preservation capacities on fish and fishery products’ spoilage. Inclusions with other preservation techniques, such as hurdle technology, for the shelf-life extension of fish and fishery products are also summarized.

Accumulation and human health risk assessment of nitrate in vegetables irrigated with different irrigation water sources- transfer evaluation of nitrate from soil to vegetables

The present study aimed to investigate the rate of accumulation, human health risk assessment, and nitrate-related transfer factor in vegetables irrigated with different sources, including treated wastewater effluent (TWE) of Kermanshah wastewater treatment plant, Gharasoo river water (RW) of Kermanshah, and well water with chemical fertilizer (WWF). For this purpose, three different types of vegetables, including basil, coriander, and radish, was cultivated, and each of them was irrigated by the three irrigation sources mentioned above. Finally, the amount of nitrate in different sources of irrigation, soil (before growing vegetables and after harvesting vegetables), and the mentioned vegetables was measured. Based on the study results, it can be concluded that the water of the Gharasoo River (RW), compared to the other two irrigation sources, causes more nitrate accumulation in the soil and vegetables grown in it. The highest transmission factor was related to basil vegetables irrigated with WWF. The results showed that the average daily intake of nitrate through the consumption of vegetables grown in Kermanshah with any irrigation water is less than the allowable amount, so the consumption of such vegetables is not dangerous to consumers' health. Therefore, it is suggested that the best irrigation source for vegetable cultivation in Kermanshah is TWE, provided that all of its physical, chemical and microbial parameters meet the standards for reuse in agriculture irrigation. Thus, the use of treated wastewater reduces the need for farmers to use chemical and organic fertilizers and cost-effectiveness, high frequency, and high availability.

Natural Food Colorants and Preservatives: A Review, a Demand, and a Challenge

The looming urgency of feeding the growing world population along with the increasing consumers' awareness and expectations have driven the evolution of food production systems and the processes and products applied in the food industry. Although substantial progress has been made on food additives, the controversy in which some of them are still shrouded has encouraged research on safer and healthier next generations. These additives can come from natural sources and confer numerous benefits for health, beyond serving the purpose of coloring or preserving, among others. As limiting factors, these additives are often related to stability, sustainability, and cost-effectiveness issues, which justify the need for innovative solutions. In this context, and with the advances witnessed in computers and computational methodologies for in silico experimental aid, the development of new safer and more efficient natural additives with dual functionality (colorant and preservative), for instance by the copigmentation phenomena, may be achieved more efficiently, circumventing the current difficulties.

Nitrate Water Contamination from Industrial Activities and Complete Denitrification as a Remediation Option

Freshwater is a scarce resource that continues to be at high risk of pollution from anthropogenic activities, requiring remediation in such cases for its continuous use. The agricultural and mining industries extensively use water and nitrogen (N)-dependent products, mainly in fertilizers and explosives, respectively, with their excess accumulating in different water bodies. Although removal of NO3 from water and soil through the application of chemical, physical, and biological methods has been studied globally, these methods seldom yield N2 gas as a desired byproduct for nitrogen cycling. These methods predominantly cause secondary contamination with deposits of chemical waste such as slurry brine, nitrite (NO2), ammonia (NH3), and nitrous oxide (N2O), which are also harmful and fastidious to remove. This review focuses on complete denitrification facilitated by bacteria as a remedial option aimed at producing nitrogen gas as a terminal byproduct. Synergistic interaction of different nitrogen metabolisms from different bacteria is highlighted, with detailed attention to the optimization of their enzymatic activities. A biotechnological approach to mitigating industrial NO3 contamination using indigenous bacteria from wastewater is proposed, holding the prospect of optimizing to the point of complete denitrification. The approach was reviewed and found to be durable, sustainable, cost effective, and environmentally friendly, as opposed to current chemical and physical water remediation technologies.

Thermoplastic starch blown films functionalized by plasticized nitrite blended with PBAT for superior oxygen barrier and active biodegradable meat packaging

Functional bioplastic packaging was produced from thermoplastic starch (TPS) with nitrite (1-5%) and polybutylene adipate terephthalate (PBAT) (PBAT/TPS at 30/70 and 40/60) via blown-film extrusion. TPS-nitrite interaction increased thermal destabilization and decreased α-relaxation temperature of TPS phase, indicating improved plasticization and disruption of starch granules. Nitrite modified C=O bonding of PBAT and improved compatibility with TPS networks, resulting in compact microstructures that reduced oxygen and water vapor permeability. Films containing nitrite showed up to 39.7% decrease (p≤0.05) in mechanical properties while effectively improving and stabilizing redness of vacuum-packaged pork during storage for 12 days. Nitrite release led to up to 0.66 ppm residual nitrite, which corresponded to formation of nitrosyl myoglobin (3.4-9.6 ppm), and effectively reduced total viable count, lactic acid bacteria and yeast and molds (p≤0.05). Stabilized lipid components also increased with increasing nitrite. Novel nitrite-containing biodegradable film enhanced functional properties and retained quality of packaged meat.

Dynamics of the ruminal microbial ecosystem, and inhibition of methanogenesis and propiogenesis in response to nitrate feeding to Holstein calves

It is known that nitrate inhibits ruminal methanogenesis, mainly through competition with hydrogenotrophic methanogens for available hydrogen (H₂) and also through toxic effects on the methanogens. However, there is limited knowledge about its effects on the others members of ruminal microbiota and their metabolites. In this study, we investigated the effects of dietary nitrate inclusion on enteric methane (CH₄) emission, temporal changes in ruminal microbiota, and fermentation in Holstein calves. Eighteen animals were maintained in individual pens for 45 d. Animals were randomly allocated to either a control (CTR) or nitrate (NIT, containing 15 g of calcium nitrate/kg dry matter) diets. Methane emissions were estimated using the sulfur hexafluoride (SF₆) tracer method. Ruminal microbiota changes and ruminal fermentation were evaluated at 0, 4, and 8 h post-feeding. In this study, feed dry matter intake (DMI) did not differ between dietary treatments (P > 0.05). Diets containing NIT reduced CH₄ emissions by 27% (g/d) and yield by 21% (g/kg DMI) compared to the CTR (P < 0.05). The pH values and total volatile fatty acids (VFA) concentration did not differ between dietary treatments (P > 0.05) but differed with time, and post-feeding (P < 0.05). Increases in the concentrations of ruminal ammonia nitrogen (NH₃–N) and acetate were observed, whereas propionate decreased at 4 h post-feeding with the NIT diet (P < 0.05). Feeding the NIT diet reduced the populations of total bacteria, total methanogens, Ruminococcus albus and Ruminococcus flavefaciens, and the abundance of Succiniclasticum, Coprococcus, Treponema, Shuttlewortia, Succinivibrio, Sharpea, Pseudobutyrivibrio, and Selenomona (P < 0.05); whereas, the population of total fungi, protozoa, Fibrobacter succinogenes, Atopobium and Erysipelotrichaceae L7A_E11 increased (P < 0.05). In conclusion, feeding nitrate reduces enteric CH₄ emissions and the methanogens population, whereas it decreases the propionate concentration and the abundance of bacteria involved in the succinate and acrylate pathways. Despite the altered fermentation profile and ruminal microbiota, DMI was not influenced by dietary nitrate. These findings suggest that nitrate has a predominantly direct effect on the reduction of methanogenesis and propionate synthesis.

Strategies for Nitrite Replacement in Fermented Sausages and Effect of High Pressure Processing against Salmonella spp. and Listeria innocua

The development of nitrite-free meat products is a current industrial concern. Many efforts have been attempted to replace the nitrite effect in cured meats colour formation and pathogens control. Our previous work evidenced that lactic acid and a cold ripening were the best hurdle technologies for nitrite-free fermented sausages from metabolomics. In the first part of this work, we investigated the effect of lactic acid compared with both two alternative additives (glucono-D-lactone and a mix of sodium di-acetate/sodium lactate) and with low-nitrite sausages, all of them following either cold or traditional ripening. For this purpose, microbiological analysis, pH, water activity (aw), and a sensory study were performed. All nitrite-free sausages (cold or traditional ripened) showed quality and safety traits similar to low-nitrite traditionally ripened ones used as control. In addition, sensory study revealed that sausages with lactic acid were the most preferred cold ripened samples, supporting that this is an optimal strategy for the production of nitrite-free sausages. We selected this product for further studies. Indeed, in the second part, we evaluated the impact of ripening, and other hurdle technologies as High Pressure Processing (HPP) and under-vacuum storage against Listeria innocua and Salmonella spp. by a challenge test. Maximal declines were obtained for ripening along with HPP (i.e., 4.74 and 3.83 log CFU/g for L. innocua and Salmonella spp., respectively), suggesting that HPP might guarantee nitrite-free sausages safety. Although the quality of raw materials remains essential, these hurdle strategies largely contributed to nitrite-free sausages safety, offering a promising tool for the meat industry.

Nitrite-enhanced copper-based Fenton reactions for biofilm removal

Unwanted biofilms present challenges for many industries. Herein an innovative biofilm removal technology was developed based on nitrite-accelerated Fenton chemistry, where both dissolved Cu ions and nano-CuO surfaces efficiently generate reactive nitrogen species as disinfectants. This simple, efficient, and cost-effective approach for biofilm removal generates important insights into Fenton chemistry, a fundamental mechanism in nature, considering the ubiquity of copper, hydrogen peroxide, and nitrite in the environment, biological systems, and various industrial processes.

Sodium nitrite detection in costal cartilage and vitreous humor - Case report of fatal poisoning with sodium nitrite

Medico-legal case reports very rarely describe sodium nitrite poisonings, but when they do most often they describe fatal suicide attempts. The case report presents a suicidal attempt with sodium nitrite of unknown provenance and the first attempt to detect nitrite ions in costal cartilage and vitreous humor samples. In February 2020, the corpse of a 23-year-old man was revealed in a student apartment. According to the prosecutor's office, the deceased had an incomplete IT (Information Technology) degree. The onsite inspection revealed the body on the bathroom floor, an opened container with sodium nitrite III in the bathroom cabinet, and a farewell letter in the apartment. The autopsy showed the hypoxia symptoms. The blood and urine of the deceased showed no trace of ethyl alcohol or psychoactive substances. Analyses showed the presence of nitrite ions in the blood (0.2 μg/ml) and urine (24.6 μg/ml) of the deceased. Additional analyses revealed nitrites presence in the gastric contents (2200 μg/ml), liver tissue (0.3 μg/g), kidney tissue (3.6 μg/g) and, for the first time, in costal cartilage (3.4 μg/g) and vitreous humor (57.7 μg/ml). The autopsy concluded that the cause of death was an acute cardio-respiratory failure in the course of suicidal sodium nitrite poisoning. The presented case indicates the need for collecting a wide range of samples for toxicological analyses. It also proves that both costal cartilage and vitreous humor may serve as an alternative forensic material in sodium nitrite poisonings.

Effects of Autochthonous Yeast Cultures on Some Quality Characteristics of Traditional Turkish Fermented Sausage "Sucuk"

The objective of this study was to determine the effects of yeast cultures (Candida zeylanoides and Debaryomyces hansenii) isolated from traditionally dry fermented Turkish sucuks, on some physicochemical and microbiological properties of the product. Eight different batches of the sucuks were produced by the inoculation of yeast and lactic acid bacteria (LAB) cultures (Lactobacillus curvatus, Lactobacillus plantarum and Lactobacillus sakei) in different combinations. The sucuks were ripened for 12 days and analyzed at 1^st, 6^th, and 12^th days of ripening. Percent moisture content, pH, water activity (a_w) and residual nitrite values of the sucuk inoculated with the yeast cultures were higher at the end of the ripening. The use of yeast cultures decreased hardness, gumminess, and chewiness values of the sucuk while increased adhesiveness values. Major volatile groups were aldehydes, terpenes, and sulphur compounds in the sucuk samples. The most noticeable results were for sensory properties of the sucuk that were positively improved by the yeast cultures.

The effect of selected lactic acid bacterial strains on the technological and microbiological quality of mechanically separated poultry meat cured with a reduced amount of sodium nitrite

The aim of the research was to estimate the effect of selected lactic acid bacterial strains on the technological quality and microbiological stability of mechanically separated poultry meat (MSPM) cured with a reduced amount of sodium nitrite. The 5 different treatments of MSPM batters were prepared: C150 - control cured with sodium nitrite at 150 mg/kg, C50 - control cured with sodium nitrite at 50 mg/kg, PL1 - cured with sodium nitrite at 50 mg/kg and inoculated Lactobacillus plantarum SCH1 at about 107 cfu/g, PL2 - cured with sodium nitrite at 50 mg/kg and inoculated Lactobacillus brevis KL5 at about 107 cfu/g, and PL3 - cured sodium nitrite at 50 mg/kg and inoculated L. plantarum S21 at about 107 cfu/g. The MSPM batters were tested at 1, 4 and 7 d of being in refrigerated storage. The scope of the research was as follows - physicochemical determinations: pH and redox, nitrates and nitrites as well as nitrosyl pigments levels, color estimation with a Comission Internationale de l'Eclairage Lab system and microbiological determinations: the total viable counts, the mesophilic lactic acid bacteria counts, Escherichia coli and Enterobacteriaceae counts. The inhibitory effect of L. plantarum SCH1 isolated from the ecological raw fermented meat product on E. coli in cured MSPM batters during refrigerated storage was proved (P < 0.05). The use of lactic acid bacterial strains in cured batters that were prepared and based on mechanically separated poultry meat did not have a negative effect on their technological quality. The positive effect of L. brevis KL5 on the level of nitrosyl pigments in the cured MSPM batters was observed (P < 0.05). The conducted research suggested the possibility of using the selected bacterial strains of the Lactobacillus genus to improve the microbiological quality of MSPM cured with a reduced amount of sodium nitrite.

S-Nitroso-N-acetylcysteine (NAC–SNO) vs. nitrite as an anti-clostridial additive for meat products

NAC–SNO is an efficient preservative against Clostridium spore germination, and under the same conditions and concentrations generates much less methaemoglobin and detectable N-nitrosoamines in the blood, in vivo.

A facile dual-function fluorescent probe for detection of phosgene and nitrite and its applications in portable chemosensor analysis and food analysis

Due to the potential threats of phosgene and nitrite to public health and safety, in this work, we first proposed the application of a facile dual-function fluorescent probe 2-(1H-Benzimidazol-2-yl)Aniline (BMA) for the detection of phosgene and nitrite in different solvent environments. BMA had fast response (1 min), high selectivity and sensitivity (the limit of detection was 1.27 nM) to phosgene in CH₃CN solution (containing 10% DMSO), which manifested as a ratiometric fluorescent mode from 416 nm to 480 nm. The response of BMA to nitrite in HCl solution (pH = 1, containing 10% CH₃CN) was also highly selective and sensitive (the limit of detection was 60.63 nM), which shown as a turn-off fluorescent mode at 485 nm. In addition, two portable chemosensors (BMA-loaded TLC plates and test strips) had also been successfully manufactured for the detection of phosgene in the gas phase and nitrite in solution, which displayed good responses. Most importantly, BMA had also been successfully used for detection of nitrite in food samples, and a good recovery (88.5%-107.2%) was obtained by adding standard sodium nitrite.

Technological parameters for the production of cooked poultry and pork sausages enriched with non-traditional vegetable raw materials

The results of the development of the technological scheme and parameters of the production of cooked sausage products from poultry and pork, enriched with protein-containing vegetable raw materials, are presented. It is proposed to introduce chickpea flour and lentil flour in a total amount of 5% in equal proportions of 1:1 into the sausage product recipe as a protein-containing vegetable additive. Previously, chickpea and lentil flour are mixed with aquafaba in different containers. Part of the water or ice introduced in the production of cooked sausages is replaced with aquafaba, obtained in the production of chickpea flour. Aquafaba is administered in an amount of 5%. These mixtures are placed in the freezer 30 minutes before the start of cooking the minced meat and kept at a temperature of -22°C for freezing. At the third stage of cutting, a frozen mixture of aquafaba, lentil and chickpea flour is added. The processing time is 3-5 minutes. This mixture in the technological process acts as a structure-forming component and improves the organoleptic properties of the finished product. The introduced additives allow you to get a functional product with an increased content of animal and vegetable protein, as well as increased vitamin and mineral value.

Colon Carcinogenesis: The Interplay Between Diet and Gut Microbiota

Colorectal cancer (CRC) incidence increases yearly, and is three to four times higher in developed countries compared to developing countries. The well-known risk factors have been attributed to low physical activity, overweight, obesity, dietary consumption including excessive consumption of red processed meats, alcohol, and low dietary fiber content. There is growing evidence of the interplay between diet and gut microbiota in CRC carcinogenesis. Although there appears to be a direct causal role for gut microbes in the development of CRC in some animal models, the link between diet, gut microbes, and colonic carcinogenesis has been established largely as an association rather than as a cause-and-effect relationship. This is especially true for human studies. As essential dietary factors influence CRC risk, the role of proteins, carbohydrates, fat, and their end products are considered as part of the interplay between diet and gut microbiota. The underlying molecular mechanisms of colon carcinogenesis mediated by gut microbiota are also discussed. Human biological responses such as inflammation, oxidative stress, deoxyribonucleic acid (DNA) damage can all influence dysbiosis and consequently CRC carcinogenesis. Dysbiosis could add to CRC risk by shifting the effect of dietary components toward promoting a colonic neoplasm together with interacting with gut microbiota. It follows that dietary intervention and gut microbiota modulation may play a vital role in reducing CRC risk.

Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes

Fatty acid nitroalkenes (NO₂-FA) are endogenously-generated products of the reaction of metabolic and inflammatory-derived nitrogen dioxide (^.NO₂) with unsaturated fatty acids. These species mediate signaling actions and induce adaptive responses in preclinical models of inflammatory and metabolic diseases. The nitroalkene substituent possesses an electrophilic nature, resulting in rapid and reversible reactions with biological nucleophiles such as cysteine, thus supporting post-translational modifications (PTM) of proteins having susceptible nucleophilic centers. These reactions contribute to enzyme regulation, modulation of inflammation and cell proliferation and the regulation of gene expression responses. Herein, focus is placed on the reduction-oxidation (redox) characteristics and stability of specific NO₂-FA regioisomers having biological and clinical relevance; nitro-oleic acid (NO₂-OA), bis-allylic nitro-linoleic acid (NO₂-LA) and the conjugated diene-containing nitro-conjugated linoleic acid (NO₂-cLA). Cyclic and alternating-current voltammetry and chronopotentiometry were used to the study of reduction potentials of these NO₂-FA. R-NO₂ reduction was observed around -0.8 V (vs. Ag/AgCl/3 M KCl) and is related to relative NO₂-FA electrophilicity. This reduction process could be utilized for the evaluation of NO₂-FA stability in aqueous milieu, shown herein to be pH dependent. In addition, electron paramagnetic resonance (EPR) spectroscopy was used to define the stability of the nitroalkene moiety under aqueous conditions, specifically under conditions where nitric oxide (^.NO) release could be detected. The experimental data were supported by density functional theory calculations using 6-311++G (d,p) basis set and B3LYP functional. Based on experimental and computational approaches, the relative electrophilicities of these NO₂-FA are NO₂-cLA >> NO₂-LA > NO₂-OA. Micellarization and vesiculation largely define these biophysical characteristics in aqueous, nucleophile-free conditions. At concentrations below the critical micellar concentration (CMC), monomeric NO₂-FA predominate, while at greater concentrations a micellar phase consisting of self-assembled lipid structures predominates. The CMC, determined by dynamic light scattering in 0.1 M phosphate buffer (pH 7.4) at 25 °C, was 6.9 (NO₂-LA) 10.6 (NO₂-OA) and 42.3 μM (NO₂-cLA), respectively. In aggregate, this study provides new insight into the biophysical properties of NO₂-FA that are important for better understanding the cell signaling and pharmacological potential of this class of mediators.

Nitrite Production from Nitrate and Its Link with Lactate Metabolism in Oral Veillonella spp

Veillonella species are among the major anaerobes in the oral cavity and are frequently detected in both caries lesions and healthy oral microbiomes. They possess the ability to utilize lactate and convert nitrate (NO₃ ^-) into nitrite (NO₂ ^-). Recently, interest in NO₂ ^- has increased rapidly because of its beneficial effects on oral and general health; i.e., it inhibits the growth and metabolism of oral pathogenic bacteria, such as Streptococcus mutans, and lowers systemic blood pressure. However, there is only limited information about the biochemical characteristics of NO₂ ^- production by Veillonella species. We found that NO₃ ^- did not inhibit the growth of Veillonella atypica or Veillonella parvula, and it inhibited the growth of Streptococcus mutans only at a high concentration (100 mM). However, NO₂ ^- inhibited the growth of Streptococcus mutans at a low concentration (0.5 mM), while a higher concentration of NO₂ ^- (20 mM) was needed to inhibit the growth of Veillonella species. NO₂ ^- production by Veillonella species was increased by environmental factors (lactate, acidic pH, and anaerobic conditions) and growth conditions (the presence of NO₃ ^- or NO₂ ^-) and was linked to anaerobic lactate metabolism. A stoichiometric evaluation revealed that NO₃ ^- is reduced to NO₂ ^- by accepting reducing power derived from the oxidization of lactate. These findings suggest that the biochemical characteristics of NO₂ ^- production from NO₃ ^- and its linkage with lactate metabolism in oral Veillonella species may play a key role in maintaining good oral and general health.IMPORTANCE The prevalence of dental caries is still high around the world. Dental caries is initiated when the teeth are exposed to acid, such as lactic acid, produced via carbohydrate metabolism by acidogenic microorganisms. Veillonella species, which are among the major oral microorganisms, are considered to be beneficial bacteria due to their ability to convert lactic acid to weaker acids and to produce NO₂ ^- from NO₃ ^-, which is thought to be good for both oral and general health. Therefore, it is clear that there is a need to elucidate the biochemical characteristics of NO₂ ^- production in Veillonella species. The significance of our research is that we have found that lactate metabolism is linked to NO₂ ^- production by Veillonella species in the environment found in the oral cavity. This study suggests that Veillonella species are potential candidates for maintaining oral and general health.

Validation of an Analytical Method for Nitrite and Nitrate Determination in Meat Foods for Infants by Ion Chromatography with Conductivity Detection

Nitrate and nitrite as sodium or potassium salts are usually added to meat products to develop the characteristic flavor, to inhibit the growth of microorganisms (particularly Clostridium botulinum), and effectively control rancidity by inhibiting lipid oxidation. However, both nitrate and nitrite ions need to be monitored for ensuring the quality and safety of cured meats. In this work, for the first time the content of nitrite and nitrate ions in homogenized meat samples of baby foods was determined by a validated method based on ion chromatography (IC) coupled with conductivity detection. Recoveries of nitrate and nitrite ions in meat samples were not lower than 84 ± 6%. The detection limits of nitrate and nitrite were 0.08 mg L⁻¹ and 0.13 mg L⁻¹, respectively. Five commercial samples of homogenized meat, namely lamb, rabbit, chicken, veal, and beef, for infant feeding were investigated; while nitrite content was below the detection limit, nitrate ranged from 10.7 to 21.0 mg kg⁻¹. The results indicated that nitrate contents were below the European (EU) fixed value of 200 mg kg⁻¹, and an acceptable daily intake of 3.7 mg kg⁻¹ was estimated.

Development of paper-based microfluidic device for the determination of nitrite in meat

This study employed the use of a microfluidic paper-based analytical device (µPAD) to determine the concentration of nitrite in pork and enhanced the limit of detection by analyzing the coffee-ring effect. The µPAD was fabricated by designing and embedding wax channels onto the cellulose-based filter paper through printing and subjecting the paper to heat treatment to allow wax penetration. Nitrite concentration was determined by monitoring the colorimetric reaction that occurred between nitrite and the added Griess reagent. The limit of detection of this device for nitrite in pork was determined to be 19.2 mg kg^-1 by analyzing the inner-chamber reaction, while it could be as low as 1.1 mg kg^-1 if the coffee-ring region was analyzed. The overall analysis could be completed within 15 min. This µPAD-based method has potential applications to routinely screen the nitrite concentration of meat products and ensure food safety and consumer health.

The nitrate content of fresh and cooked vegetables and their health-related risks

BACKGROUND

Vegetables are the most important source of nitrates in the human diet. During various processes in the body, nitrates are converted into nitrites, which causes various diseases, such as blue baby syndrome and cancer. This study aimed to determine the concentration of nitrates in several vegetable farms in Sanandaj city and to evaluate their health-related risks.

METHODS

This descriptive cross-sectional study was conducted from October 2017 to July 2018. A total of 90 samples were taken from nine farms. Soil and water sampling was also carried out. All stages of sample preparation and extraction were carried out according to Food Standards 2-16721, and the nitrate measurements were performed using ion chromatography (Compact IC Plus 882 Model, Metrohm, Switzerland). A health risk assessment was performed using the non-carcinogenic risk assessment.

RESULTS

This study's results showed that the nitrate concertation in all vegetables was less than National Iranian Vegetable Nitrate Standard. Nitrate levels in leafy vegetables were higher than in root vegetables, and the root vegetables levels were higher than those in Fruit vegetable. The nitrate level in vegetables in autumn was higher than in spring. The cooking process reduced the raw vegetables' nitrate content from 4.094% to 13.407%, while the frying process increased the vegetables' nitrate content from 12.46% to 29.93%. The highest health risk level in raw, cooked and fried vegetables was parsley, parsley and beet leaves, respectively, and the lowest in all categories was tomatoes. Generally, the highest health risk was related to fried beet leaves, and the lowest was raw tomatoes. In addition, each of the abovementioned relationships between vegetables' nitrate levels and the harvest season, type of processing procedure and type of vegetables was significant (p < 0.05). The irrigation water's nitrate concentration in all fields was between 12.36 and 33.14 mg/l. The soil contained nitrate levels of between 4.35 and 9.7 mg/kg.

CONCLUSION

Based on this study, we can conclude that the amount of nitrates in raw vegetables was lower than the standard limit's level and that this level does not cause health problems for consumers.

New Microbe Killers: Self-Assembled Silver(I) Coordination Polymers Driven by a Cagelike Aminophosphine

New Ag(I) coordination polymers, formulated as [Ag(µ-PTAH)(NO3)2]n (1) and [Ag(µ-PTA)(NO2)]n (2), were self-assembled as light- and air-stable microcrystalline solids and fully characterized by NMR and IR spectroscopy, electrospray ionization mass spectrometry (ESI-MS(±), elemental analysis, powder (PXRD) and single-crystal X-ray diffraction. Their crystal structures reveal resembling 1D metal-ligand chains that are driven by the 1,3,5-triaza-7-phospaadamantane (PTA) linkers and supported by terminal nitrate or nitrite ligands; these chains were classified within a 2C1 topological type. Additionally, the structure of 1 features a 1D→2D network extension through intermolecular hydrogen bonds, forming a two-dimensional hydrogen-bonded network with fes topology. Furthermore, both products 1 and 2 exhibit remarkable antimicrobial activity against different human pathogen bacteria (S. aureus, E. coli, and P. aeruginosa) and yeast (C. albicans), which is significantly superior to the activity of silver(I) nitrate as a reference topical antimicrobial.

Anti-Biofilm Effect of Selected Essential Oils and Main Components on Mono- and Polymicrobic Bacterial Cultures

Biofilms are surface-associated microbial communities resistant to sanitizers and antimicrobials. Various interactions that can contribute to increased resistance occur between the populations in biofilms. These relationships are the focus of a range of studies dealing with biofilm-associated infections and food spoilage. The present study investigated the effects of cinnamon (Cinnamomum zeylanicum), marjoram (Origanum majorana), and thyme (Thymus vulgaris) essential oils (EOs) and their main components, i.e., trans-cinnamaldehyde, terpinen-4-ol, and thymol, respectively, on single- and dual-species biofilms of Escherichia coli, Listeria monocytogenes, Pseudomonas putida, and Staphylococcus aureus. In dual-species biofilms, L. monocytogenes was paired with each of the other three bacteria. Minimum inhibitory concentration (MIC) values for the individual bacteria ranged between 0.25 and 20 mg/mL, and trans-cinnamaldehyde and cinnamon showed the highest growth inhibitory effect. Single-species biofilms of L. monocytogenes, P. putida, and S. aureus were inhibited by the tested EOs and their components at sub-lethal concentrations. Scanning electron microscopy images showed that the three-dimensional structure of mature biofilms embedded in the exopolysaccharide matrix disappeared or was limited to micro-colonies with a simplified structure. In most dual-species biofilms, to eliminate living cells from the matrix, concentrations exceeding the MIC determined for individual bacteria were required.

One-Step Polylactic Acid Screen-Printing Microfluidic Paper-Based Analytical Device: Application for Simultaneous Detection of Nitrite and Nitrate in Food Samples

In this work, we report a one-step approach for fabricating screened-printed microfluidic paper-based analytical devices (μPADs) using polylactic acid as a new hydrophobic material. A polylactic acid solution was screen printed onto chromatography papers to create hydrophobic patterns for fluidic channels. The optimal polylactic acid concentration for successful device fabrication is 9% w/v. The μPADs were fabricated within 2 min and provided high reproducibility and stability. The utility of polylactic acid screen-printing was demonstrated for the simultaneous detection of nitrite and nitrate using colorimetric detection. Under optimized experimental conditions, the detection limits and the linear ranges, respectively, were 1.2 mg L−1 and 2–10 mg L−1 for nitrite and 3.6 mg L−1 and 10–50 mg L−1 for nitrate. The detection times for both ions were found to be within 12 min. The developed μPAD was applied for the simultaneous determination of these ions in food samples, and no significant differences in the analytical results were observed compared to those of the reference method. The polylactic acid screen-printing approach presented here provides a simple, rapid, and cost-effective alternative fabrication method for fabricating μPADs.