FIA evaluation of nitrite and nitrate contents of liver pâtés

A comparative study on the nitrite and nitrate contents of 15 liver pâté brands, in a total of 45 samples (three batches per brand) is presented. The study was conducted on two different kind of pâtés: pork liver pâtés and fowl liver pâtés. For the simultaneous determination of nitrite and nitrate, an automated flow injection system with spectrophotometric detection was used. The manifold was based on the splitting of the flow after injection and subsequent confluence of the flow before reaching the detector, allowing the reduction of nitrate to nitrite in part of the sample plug on an on-line copper cadmium reductor column. Spectrophotometric determination was made after a diazotization coupling reaction. The levels of nitrites and nitrates ranged from 1.07 mg NaNO₂ kg⁻¹ ± 0.43 to 15.9 mg NaNO₂ kg⁻¹ ± 5.2 and from 24.5 mg NaNO₃ kg⁻¹ ± 2.7 to 207 mg NaNO₃ kg⁻¹ ± 14, respectively. The levels of concentration of these constituents were below the allowable limits. A significant dispersion in the results was observed between different brands and within some of the brands.     

Culture and molecular identification of fungal contaminants in edible bird nests

Widespread food poisoning due to microbial contamination has been a major concern for the food industry, consumers and governing authorities. This study is designed to determine the levels of fungal contamination in edible bird nests (EBNs) using culture and molecular techniques. Raw EBNs were collected from five house farms, and commercial EBNs were purchased from five Chinese traditional medicine shops (companies A–E) in Peninsular Malaysia. The fungal contents in the raw and commercial EBNs, and boiled and unboiled EBNs were determined. Culturable fungi were isolated and identified. In this study, the use of these methods revealed that all EBNs had fungal colony-forming units (CFUs) that exceeded the limit set by Standards and Industrial Research Institute of Malaysia (SIRIM) for yeast and moulds in EBNs. There was a significant difference (p < 0.05) in the number of types of fungi isolated from raw and commercial EBNs, but no significant difference in the reduction of the number of types of fungi after boiling the EBNs (p > 0.05). The types of fungi isolated from the unboiled raw EBNs were mainly soil, plant and environmental fungi, while the types of fungi isolated from the boiled raw EBNs, unboiled and boiled commercial EBNs were mainly environmental fungi. Aspergillus sp., Candida sp., Cladosporium sp., Neurospora sp. and Penicillum sp. were the most common fungi isolated from the unboiled and boiled raw and commercial EBNs. Some of these fungi are mycotoxin producers and cause opportunistic infections in humans. Further studies to determine the mycotoxin levels and methods to prevent or remove these contaminations from EBNs for safe consumption are necessary. The establishment and implementation of stringent regulations for the standards of EBNs should be regularly updated and monitored to improve the quality of the EBNs and consumer safety.     

Nitrate and nitrite in vegetables from areas affected by war-time operations in Croatia

To evaluate nitrate and nitrite contents in cabbage and potatoes, the most consumed vegetables in Croatia, and to examine if war-time operations in Croatia affected nitrate and nitrite levels in vegetables, potatoes and cabbage cultivated in the war region (East Slavonia) and out of war regions were analyzed. Data showed that nitrate contents were higher in the samples from the war region (32% and 24% in potatoes and cabbage, respectively) but differences were not statistically significant. The nitrate levels found in potato samples (196 mg NaNO₃/kg fresh weight (FW) and cabbage samples (911 mg NaNO₃/kg FW) were comparable with levels reported for other countries. The nitrite contents in potatoes (321 μg NaNO₂/kg FW) and cabbage (173 μg NaNO₂/kg FW) were lower than the contents reported for most other countries. Further examinations of nitrate and nitrite concentrations in vegetables in Croatia as well as examinations of the influence of war-time operations on accumulation of these toxic contaminants are necessary.     

Farbreagenz zur Unterscheidung von Weißeichen- und Roteichenholz

Among the approximately 250 recognized oak species only about 20 to 30 are of major economic importance, nearly all of them decidous trees. Owing to constant differences in certain properties among these oaks two commercial groups are generally acknowledged: The white oaks and the red oaks. The two groups cannot be safely distinguished by relying solely on wood surface characters. Rather, this objective is accomplished by applying a 5% sodium nitrite (NaNO₂) solution to a clean surface (cross section). On white oak this substance changes colour to a dark brown while on red oak a light brown prevails. Laboratory trials with NaNO₂ resulted in a correct attribution of 95% of all samples tested. Additional information is presented regarding the practical application of this method of white and red oak differentiation.     

Effects of nitrates and nitrites on Lactobacillus helveticus and Lactobacillus casei dairy cultures

 The aim of this work was to observe the effects of nitrites and nitrates on the titratable acidity of milk after addition of Lactobacillus helveticus (TX 121) and L. casei (CAD 154) dairy cultures and on the levels of nitrate and nitrite. After adding L. helveticus and nitrites the increasing concentrations of the latter brought about a marked decrease in titratable acidity. In milk containing 100 mg·kg^–1 nitrite the resulting concentration was 39.33 mg·kg^–1 NaNO₂. Nitrates caused a less obvious decrease in titratable acidity, giving 13.27 g·l^–1 lactic acid. In milk containing 100 mg·kg^–1 NaNO₃ the resulting concentration was 24.99 mg·kg^–1 NaNO₃. Experiments with L. casei and a nitrite additive revealed a decrease in titratable acidity to 8.89 g·l^–1 lactic acid. After incubation, nitrite levels were reduced from 100 mg·kg^–1 NaNO₂ to 37.81 mg·kg^–1 NaNO₂. Nitrates were also stated to inhibit the titratable acidity of the sample, which decreased to 11.42 g·l^–1 lactic acid. Nitrates were reduced to 46.99 mg·kg^–1 NaNO₃. The present study shows that nitrites, more than nitrates decrease the titratable acidity of milk after addition of L. helveticus and L. casei dairy cultures. A reduction of nitrates and nitrites in milk samples by Lactobacillus was also found. The results of this study can be used in the dairy industry in the production of several types of hard cheese as well as fermented milk products that use L. helveticus and L. casei dairy cultures. Received: 31 March 1999 / Revised version: 6 September 1999     

Effect of nitrapyrin on nitrapyrin residues and nitrate content in red beet roots fertilised with urea

The effect of nitrapyrin [2-chloro-6-(trichloromethyl)pyridine] application on nitrapyrin residues and nitrate content in red beet (Beta vulgaris L. var. conditiva) roots and in soil fertilised with urea was studied during the 1977 growing season. The nitrapyrin residues in roots were on 15 August between 0.00–1.19 μg g^?1 and on 1 October between 0.00–0.45 μg g^?1 (dry weight basis) correlating significantly r = 0.99, P<0.01) to the rates of nitrapyrin applied on 8 June (0–34 kg ha^?1). The content of nitrapyrin in roots decreased in autumn having in August-September a ‘biological half-life’ of 3 weeks. In soil the same parameter was in July-September more than 4 months. The ratio of nitrapyrin to its main breakdown product varied in soil between 3.5–24.8 and in red beets between 0.6–1.4. Neither of these compounds were found in processed canned red beets. Nitrapyrin treatment decreased the nitrate content in both soil and beets. The inhibitor application of 18 kg ha^?1 caused the highest reduction of the NO₃-nitrogen content in beets, the average values on dry weight basis being 0.51–0.34 mg g^?1 for 0–18 kg ha^?1 nitrapyrin application, respectively. The reduction of NO₃-nitrogen in beets from its level of 15 August to its September level was 44%. After 5 September the reduction of the nitrate level in beets was not significant.     

Nitrate and Nitrite levels in carrot roots

The nitrate and nitrite levels were determined in two carrot varieties, cultivated in three Experimental Stations of Varieties Assessment in different regions of Poland in 1987–1989. The results obtained were analysed against soil conditions (kind and composition, richness), agrotechnical background (length of vegetation period, harvest time) and climatic conditions (air temperature and precipitation). The nitrate level in carrot was estimated at av. 349 mg KNO₃/kg. Significant differences were found in nitrate levels depending on place and year of cultivation. The most significant effects of the studied factors on the nitrate level had soil richness in potassium and magnesium as well as length of vegetation period. The studied carrot displayed a high level of nitrites (av. 3.1 mg NaNO₂/kg), which might have resulted from a microbiological reduction of nitrates occurring between harvest and the time of performing analyses.     

Characterization and expression analysis of a gene cluster for nitrate assimilation from the yeast Arxula adeninivorans

In Arxula adeninivorans nitrate assimilation is mediated by the combined actions of a nitrate transporter, a nitrate reductase and a nitrite reductase. Single‐copy genes for these activities (AYNT1, AYNR1, AYNI1, respectively) form a 9103 bp gene cluster localized on chromosome 2. The 3210 bp AYNI1 ORF codes for a protein of 1070 amino acids, which exhibits a high degree of identity to nitrite reductases from the yeasts Pichia anomala (58%), Hansenula polymorpha (58%) and Dekkera bruxellensis (54%). The second ORF (AYNR1, 2535 bp) encodes a nitrate reductase of 845 residues that shows significant (51%) identity to nitrate reductases of P. anomala and H. polymorpha. The third ORF in the cluster (AYNT1, 1518 bp) specifies a nitrate transporter with 506 amino acids, which is 46% identical to that of H. polymorpha. The three genes are independently expressed upon induction with NaNO₃. We quantitatively analysed the promoter activities by qRT–PCR and after fusing individual promoter fragments to the phytase (phyK) gene from Klebsiella sp. ASR1. The AYNI1 promoter was found to exhibit the highest activity, followed by the AYNT1 and AYNR1 elements. Direct measurements of nitrate and nitrite reductase activities performed after induction with NaNO₃ are compatible with these results. Both enzymes show optimal activity at around 42°C and near‐neutral pH, and require FAD as a co‐factor and NADPH as electron donor. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of reducing nitrate and nitrite added to dry fermented sausages on the survival of Salmonella Typhimurium

Salmonella is one of the pathogens that most frequently contaminate pork processing lines. Several hurdles can control this organism in dry fermented sausages, among them is nitrite. However, the traditional use of nitrate/nitrite in the meat industry is being questioned due to their involvement in nitrosamine formation. In this study, minced pork and sausages inoculated with Salmonella Typhimurium were prepared with 150 ppm NaNO₃ and 150 ppm NaNO₂ (maximum amounts allowed by EU), and with a reduction of 25% and 50%. The absence of nitrate/nitrite favored Salmonella growth, with 2–2.5 log cfu/g higher counts at the end of ripening, compared to nitrate/nitrite added batches. The 50% reduction showed the same inhibitory effect as the maximum amounts. Nitrate/nitrite represented an essential hurdle to control Salmonella even when pH and a_w were below the values considered as minimum for its growth. The effect of this reduction on other pathogens should be considered.     

Effects of nitrite levels,endpoint temperature and storage on pink color development in turkey rolls

The objective of this research was to determine the relationship between minimum nitrite level, endpoint temperature and storage period on pink discoloration of turkey rolls. Rolls were prepared with 0, 3 or 5 parts per million (ppm) NO₂^–, cooked to an endpoint temperature of 75 °C or 85 °C and stored at 4 °C. During the 13-day storage period, on the 0th, 4th, 8th and 13th days cured pigment, total pigment, residual nitrite and color parameters were measured and sensory color was evaluated. At each endpoint temperature, addition of 3 ppm or 5 ppm NO₂^– significantly increased cured pigment and total pigment levels. Cured pigment levels of turkey rolls cooked to 75 °C were higher than rolls cooked to 85 °C, regardless of the NO₂^– level. There was a significant decrease in cured pigment levels at the end of the storage period (13th day). Analysis of residual NO₂^– in all treatment groups showed no detectable amounts. Endpoint temperature and addition of NO₂^– affected L* values: rolls cooked to the 75 °C endpoint had higher L* values. The additon of nitrite with the 75 °C endpoint temperature resulted in higher a* values. a* values also increased during the storage. The higher endpoint temperature (85 °C) resulted in lower a* values. Yellowness was not affected by final cooking temperature. Both the addition of NO₂^– and storage decreased b* values. The panel found no differences in pinkness intensity between the two levels of added nitrite (3 and 5 ppm). Sensory pinkness intensity in nitrite-added samples increased with increasing storage.     

Survival of Listeria innocua in dry fermented sausages and changes in the typical microbiota and volatile profile as affected by the concentration of nitrate and nitrite

The involvement of nitrate and nitrite in the formation of N-nitrosamines in foods is a matter of great concern. This situation has led to revise the real amount of nitrate and nitrite needed in meat products to exert proper technological and safety activities, and also to extensive research to find alternatives to their use. The present study addresses the possibility of reducing the ingoing amounts of these additives below the legal limits established by the current European regulations. Different concentrations of nitrate and nitrite were tested on Spanish salchichón-type dry fermented sausages concerning their role in the microbiota and volatile profile. Sausages were manufactured with the maximum ingoing amounts established by the EU regulations (150 ppm NaNO₃ and 150 ppm NaNO₂), a 25% reduction and a 50% reduction; control sausages with no nitrate/nitrite addition were also prepared. The mixtures were inoculated with 5 log cfu/g of Listeria innocua as a surrogate for Listeria monocytogenes. L. innocua numbers in the final product were approximately 1.5 log cfu/g lower in the batch with the maximum nitrate/nitrite concentration when compared to 25 and 50% reduced batches, and about 2 log cfu/g in comparison to the control sausages. The final numbers of catalase-positive cocci were 1 log cfu/g higher in the 50% nitrate/nitrite reduced batch and 2 log cfu/g higher in the control sausages, compared to products manufactured with the maximum nitrate/nitrite concentration. This increase was related to a higher amount of volatile compounds derived from carbohydrate fermentation and amino acid degradation. Sausages with no addition of nitrate/nitrite showed higher amount of volatiles from lipid oxidation. Enterobacteriaceae counts reached detectable values (1-2 log cfu/g) in both nitrate/nitrite reduced sausages and in the control batch, while these organisms were not detected in the batch with the maximum ingoing amount. Nitrate and nitrite exerted a significant effect on the typical microbiota of dry fermented sausages and effectively contributed to control Listeria. These considerations should be taken into account in view of a future restriction in the use of these curing additives.     

Aroma, Color, and Lipid Oxidation of Turkey Muscle Emulsions

Turkey emulsions were prepared with (1) no additives, (2) sodium chloride (NaCl), (3) sodium nitrite (NaNO₂), (4) sodium ascorbate (NaAsc), or (5) both NaNO₂ and NaAsc. Raw and cooked emulsions from each of the five treatments were stored (?18°C) and then evaluated before and after heating. Emulsions with NaNO₂ and NaAsc contained less malonaldehyde than those with NaCl or no additive and raw turkey emulsions generally contained less malonaldehyde than cooked. Nitrite was the additive that produced the major effect on color of heated emulsions. Generally, emulsions containing both NaNO₂ and NaAsc had the most meaty aroma and the least stale aroma. Emulsions with NaCl tended to have greater stale aroma.     

Effect of freeze-dried leek powder (FDLP) and nitrite level on processing and quality characteristics of fermented sausages

Fermented sausages were produced with 0.84% and 1.68% freeze-dried leek powder (FDLP), providing 75 and 150 mg/kg NaNO₃, respectively, and three levels of added nitrite (0, 75, and 150 mg/kg NaNO₂). A control treatment was also produced with 150 mg/kg NaNO₂. Sausages with FDLP were darker and yellower (p < 0.05) than the control. Higher FDLP levels produced less red, yellower and darker sausages (p < 0.05). Lower FDLP levels resulted in higher (p < 0.05) sensory scores for external appearance, flavour and overall acceptability. No differences were found among the treatments with FDLP plus 75 or 150 ppm NaNO₂ in TBA value, lightness, redness (cross section), redness stability, yellowness, texture parameters and sensory firmness, flavour and overall acceptability. The use of 0.84% FDLP and 75 ppm NaNO₂ is considered more appropriate for the production of fermented sausages, as it results in a 50% reduction in added nitrite.     

A lysimeter study of nitrate leaching, optimum fertilisation rate and growth responses of corn (Zea mays L.) following soil amendment with water-saving super-absorbent polymer

BACKGROUND: Nitrate leaching and the resulting groundwater contamination from intensive cereal production has become a major concern for long‐term farmland efficiency and environmental sustainability in northern China. The aim of this study was to evaluate a water‐saving super‐absorbent polymer (SAP) for minimising NO₃^? leaching from soil and optimising corn growth and yield. Thirty‐six undisturbed soil lysimeters were installed in a field lysimeter facility in drought‐affected northern China to study the growth and yield characteristics of summer corn (Zea mays L.) as well as the amount of NO₃–leaching losses under different fertiliser (standard, medium or 75% and low, or 50% of conventional fertilisation rate) and SAP (control, 0; level‐1, 15 kg ha^?1 and level‐2, 30 kg ha^?1) treatments. RESULTS: Corn yield fell by 19.7% under medium and 37.7% under low fertilisation; the application of SAP increased yield significantly by 44.4% on level‐1 and 80.3% on level‐2. Similarly, plant height, leaf area, number of grains as well as protein, soluble sugar and starch contents in the grain also increased with SAP treatment. Application of SAP at 30 kg ha^?1 plus half of conventional fertilisation can reduce maximum (64.1%) nitrate leaching losses from soil. CONCLUSIONS: Application of SAP at 30 kg ha^?1 plus only half the amount of conventional fertiliser rate (150 kg urea, and 50 kg each of superphosphate and potassium sulfate) would be a more appropriate practice both for minimising nitrate leaching and sustainable corn production under the arid and semiarid conditions of northern China. Copyright © 2011 Society of Chemical Industry     

Nitrate and nitrite contents in Cuban cheese of the Gouda type

The nitrate and nitrite contents in cheese of the Gouda type, produced by the Milk Complex of Havanna, were investigated and compared with those found in 5 types of imported cheese consumed in Cuba. No significant differences were found in the mean value (x) of NaNO₃, whereas in the mean value (x) of NaNO₂ differences were found when comparing all cheeses against each other. From these results it is inferred that the consumption of Gouda type cheese does not represent an important contribution to the daily intake of nitrates and nitrites, precursors in the synthesis of cancerogenic N-nitroso compounds.     

Influence of nitrogen form on yield and nitrate content of subirrigated early potato

Potato is classified among the vegetables with low nitrate content but, in diet, it contributes most to the daily intake of nitrate, because of its high per capita consumption. Two trials were carried out in winter–spring and autumn–winter cycles using a trough bench subirrigation system. Potato seedlings were transplanted into pots containing peat, pumice and vermiculite in a 3:1:1 volume ratio. Both trials were carried out to compare three nutrient solutions having the same nitrogen concentration (6.4 mM ), but different ammonium:nitrate (NH₄‐N:NO₃‐N) percentage ratios (100:0, 50:50 and 0:100). In the winter–spring cycle, tubers were lower in weight and were more numerous than in the autumn–winter cycle. The tuber yield of ammonium‐fed plants was lower than with the mixed form and 100% NO₃‐N, but only in the trial carried out in the winter–spring period. Nitrate‐fed plants yielded a number of tubers almost 3‐fold higher than ammonium‐fed plants. The NO₃ content of tubers harvested in spring in the presence of 100% NH₄‐N in the nutrient solution was a 25% of that in nitrate‐fed plants (44 vs 169 mg kg^?1 of fresh mass); in tubers harvested in winter, with worse light conditions, nitrate content increased with increasing NO₃‐N in the nutrient solution (26, 109, and 225 mg kg^?1 of fresh mass with NH₄‐N:NO₃‐N 100:0, 50:50 and 0:100, respectively). The substrate electrical conductivity increased with increasing ammonium concentration in the nutrient solution, and was higher in the upper layer of the substrate. Copyright © 2004 Society of Chemical Industry     

Vitamin (B1, B2, B3 and B6) content and oxidative stability of Gastrocnemius muscle from dry-cured hams elaborated with different nitrifying salt contents and by two ageing times

The effect of the amount of added nitrate and nitrate plus nitrite to dry-cured hams on the vitamin (B1, B2, B3, B6) content, the antioxidant enzyme superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx) activities and the thiobarbituric acid reactive substances (TBARS) was assessed in Gastrocnemius muscle at the end of two ripening processes. Five different curing mixtures (Hi–N: 600 KNO₃; Lo–N: 150 KNO₃; Hi–Mix: 600 KNO₃ + 600 NaNO₂; Lo–Mix: 150 KNO₃ + 150 NaNO₂; Hi–Mix/Asc: 600 KNO₃ + 600 NaNO₂ + 500 sodium ascorbate, expressed as mg of salts added on surface per kg of fresh ham) were evaluated in dry-cured hams aged for 11.5 months (standard process, SP) and 22 months (long process, LP).     

The role of monoxide hemoglobin in color improvement of chicken sausage

The role of monoxide hemoglobin (COHb) in improvement of chicken sausage color was investigated. COHb and NaNO₂ synergistically increased a* values. Addition of 0.1% COHb decreased the residual nitrite content in the presence of 0.001% NaNO₂. Compared with controls, the combined treatment resulted in significantly higher nitroso pigment contents while the single treatment resulted in slightly higher nitroso pigment contents. Visible spectrometry indicated that both nitrosohemochrome (NH) and hematin were the main ingredients of pigments extracted from chicken sausage treated with a combination of 0.006% NaNO₂ and 0.6% COHb. Formation of NH and hematin caused an increase in a* values and a decrease in L* values, respectively. COHb showed potential for use in meat product formulations.     

Enzyme immunoassay for the detection of porcine gelatine in edible bird’s nests

Porcine gelatine is a common adulterant found in edible bird’s nests (EBNs) used to increase the net weight prior to sale. This study aimed to develop indirect enzyme-linked immunosorbent assays (ELISAs) for porcine gelatine adulteration using anti-peptide polyclonal antibodies. Three indirect ELISAs were developed (PAB1, 2 and 3), which had limits of detection (LODs) of 0.12, 0.10 and 0.11 µg g^–1, respectively. When applied to standard solutions of porcine gelatine, the inter- and intra-assays showed coefficients of variation (CVs) less than 20% and were able to detect at least 0.5 ng µg^–1 (0.05%) porcine gelatine in spiked samples. The proposed ELISA offers attractions for quality control in the EBN industry.     

The Nitrite‐Scavenging Properties of Catechol,Resorcinol, and Hydroquinone: A Comparative Study on Their Nitration and Nitrosation Reactions

The nitration and nitrosation reactions of catechol, resorcinol, and hydroquinone (0.05 mmol/L) with sodium nitrite (0.05 mmol/L) at pH 3 and 37 °C were studied by using liquid chromatography and mass spectrometry (LC‐MS) and atom charge analysis, which was aimed to provide chemical insight into the nitrite‐scavenging behavior of polyphenols. The 3 benzenediols showed different mechanisms to scavenge nitrite due to their differences in hydroxyl position. Catechol was nitrated with 1 NO₂ group at the hydroxyl oxygen, and resorcinol was nitrosated with 2 NO groups at the C₂ and C₄ (or C₆) positions of the benzene ring. Hydroquinone could scavenge nitrite through both nitration and nitrosation mechanisms. The nitrated hydroquinone had 1 NO₂ group at the hydroxyl oxygen in the molecule, while the nitrosated 1 containing 2 NO groups at the benzene ring might have 3 structure probabilities. The results may provide a structure‐activity understanding on the nitrite‐scavenging property of polyphenols, so as to promote their application in the food industry for the removal of possibly toxic nitrites found in many vegetables and often in processed meat products.