Comparison of three methods for determination of N-nitrosopyrrolidine in fried dry-cured bacon

The recently developed Eastern Regional Research Center ( ERRC ) dry column chromatographic procedure for determining N-nitrosopyrrolidine (NPYR) in fried cure-pumped bacon was evaluated for its applicability to fried dry-cured bacon. The method was then compared with 2 established procedures for volatile nitrosamine analysis in cured meat products: the multidetection thermal energy analyzer (MD) method and the mineral oil distillation (MOD) screening procedure. No significant difference (P less than 0.05) in NPYR values was found between the ERRC and MD procedures, but significant differences were found between the ERRC and MOD procedures and between the MOD and MD procedures. No artifactual nitrosamine formation was found in the ERRC procedure, but significant amounts were found in samples analyzed by the MOD procedure. The ERRC method was demonstrated to be rugged and very rapid. It is proposed that the ERRC method replace the MOD method as the official screening procedure for NPYR in fried bacon.     

Dry column-thermal energy analyzer method for determining N-nitrosopyrrolidine in fried bacon: collaborative study

A dry column method for isolating N-nitrosopyrrolidine (NPYR) from fried, cure-pumped bacon and detection by gas chromatography-thermal energy analyzer (TEA) was studied collaboratively. Testing the results obtained from 11 collaborators for homogeneous variances among samples resulted in splitting the nonzero samples into 2 groups of sample levels, each with similar variances. Outlying results were identified by AOAC-recommended procedures, and laboratories having outliers within a group were excluded. Results from the 9 collaborators remaining in the low group yielded coefficients of variation (CV) of 6.00% and 7.47% for repeatability and reproducibility, respectively, and the 8 collaborators remaining in the high group yielded CV values of 5.64% and 13.72%, respectively. An 85.2% overall average recovery of the N-nitrosoazetidine internal standard was obtained with an average laboratory CV of 10.5%. The method has been adopted official first action as an alternative to the mineral oil distillation-TEA screening procedure.     

Effect of N-nitrosothiazolidine-4-carboxylic acid on formation of N-nitrosothiazolidine in uncooked bacon

N-Nitrosothiazolidine-4-carboxylic acid (NTHZC) was recently identified in a variety of smoked fish and cured meat products. While the toxicological properties of NTHZC are currently unknown, it has been speculated that N-nitrosothiazolidine (NTHZ) in fried bacon may be caused in part by decarboxylation of NTHZC. A limited survey of uncooked cured meat products failed to demonstrate any correlation between levels of NTHZC and NTHZ. However, NTHZC levels were significantly higher, ranging from 8 to 1400 ppb, than the corresponding NTHZ levels, which ranged from less than 2 to 18 ppb. Decarboxylation of NTHZC to NTHZ in a model system occurs at 110 degrees C, which is significantly higher than the average bacon processing temperature of 54 degrees C, but lower than the normal frying temperature of 177 degrees C recommended for bacon. Results from both model system and frying experiments with NTHZC and its precursors suggest that NTHZC decarboxylation to NTHZ is not the principal pathway to NTHZ formation in uncooked bacon.     

Mass spectrometric confirmation of the presence of N-nitrosopyrrolidine in instant coffee

Traces of N-nitrosopyrrolidine (NPYR) may occur in some samples of both instant coffee and fine-ground roasted coffee. The identity of NPYR in 2 samples of instant coffee was confirmed by mass spectrometry as well as by liquid chromatography-thermal energy analysis. A 2-step cleanup procedure, involving fractionation on basic alumina followed by gradient elution on reverse-phase C18 cartridge, is described that allows full-scan mass spectrometric confirmation of NPYR in tested samples.     

Effects of different cooking methods on antioxidant profile, antioxidant capacity, and physical characteristics of artichoke

In this study, the effects of three common cooking practices (i.e., boiling, steaming, and frying) on the artichoke phenolic compounds pattern were evaluated by LC-MS/MS analysis. The variation of carotenoids, antioxidant capacity, and artichoke physical properties after cooking was also investigated. The major phenolic compounds present in the raw sample were 5- O-caffeoylquinic and 1,5-di- O-caffeoylquinic acids; after cooking treatments, an increase of the overall caffeoylquinic acids concentration due to the formation of different dicaffeoylquinic acid isomers was observed. Steamed and fried samples showed similar patterns of dicaffeoylquinic concentrations, which were higher with respect to the boiled samples. On the other hand, all cooking practices, particularly frying, decreased flavonoid concentration. The antioxidant capacity of cooked artichokes, measured by three different assays, enormously increased after cooking, particularly after steaming (up to 15-fold) and boiling (up to 8-fold). The observed cooking effect on the artichoke antioxidant profile is probably due to matrix softening and increased extractability of compounds, but the increase of antioxidant capacity is much higher than the increase of antioxidant concentration. These results suggest that some common cooking treatments can be used to enhance the nutritional value of vegetables, increasing bioaccessibility of health-promoting constituents.     

Effects of Broad-Leaf Crop Frequency and Fungicide Application in Various Rotations on Nitrate Nitrogen and Extractable Phosphorus in a Dark Brown Soil

Flexibility in crop rotation planning allows canola and pea producers to adapt to changing management practices and marketing opportunities. Current recommendations in western Canada are to follow a 1 in 4-yr rotation for canola or pea on a particular field, but producers are interested in increasing frequency of these crops. The objective of this study was to determine the impacts of frequency of broad-leaf crops canola and pea and fungicide application in various crop rotations on accumulation and distribution of nitrate nitrogen (N) and extractable phosphorus (P) in the soil profile after 8 yr on a Dark Brown Chernozem (Typic Boroll) loam at Scott, Saskatchewan. The field experiment (from 1998 and 2005) contained monoculture canola and monoculture pea compared with rotations that contained these crops every 2, 3, and 4 yr with wheat and/or flax. Two cultivars of canola were included, an herbicide-tolerant and blackleg-resistant hybrid, and a conventional (not herbicide tolerant) open-pollinated, blackleg-susceptible (OP) cultivar. Subplots were fungicide treatments that attempted to control both blackleg and sclerotinia stem rot in canola and mycosphaerella blight in pea. Residual soil nitrate N in most layers and extractable P in many layers were significantly affected by crop rotation or rotation length, with the greatest amounts after monocultures. Fungicide application resulted in decreased amount of residual soil nitrate N, but it had no effect on soil extractable P. Crop phase (i.e., individual crops that make up the rotation) had a significant effect on soil nitrate N in many crop rotations; for example, residual soil nitrate N tended to be greatest after pea or OP canola and also after flax in the 4-yr rotation with flax. Crop phase had no effect on soil extractable P in any crop rotation. The lower amounts of residual soil nitrate N were usually associated with greater cumulative seed yields, and more so with greater cumulative N removal in seed in various crop rotations and phases within rotations. In conclusion, the findings suggest that accumulation of residual nutrients in soil, especially nitrate N, can be minimized by extending crop rotations, using high-yielding disease-resistant canola cultivars, and applying fungicides in years with weather conditions conducive to diseases.     

Effects of Frying and Microwave Heating on Decomposition of Benzoyl Peroxide in Flour

Effects of frying and microwave heating on the decomposition of benzoyl peroxides (BPO) in flour were studied. First, BPO and its main decomposition product, benzoic acid (BA), were extracted from different flour products by ultrasonication in ethanol. Next, three samples of commercial flour, two fried foods, and two microwave foods were analyzed by high performance liquid chromatography (HPLC) and mass spectrum (MS). Results revealed that the BPO content decreased after frying and microwave heating treatments. Furthermore, the existence of biphenyl in fried food was successfully verified by HPLC‐MS. Biphenyl that decomposed from BPO may be one source of toxicity in fried foods. In contrast to fried food, new components made through the special heating module were not found in microwave food.     

Current trends in levels of volatile N-nitrosamines in fried bacon and fried-out bacon fat

Commercially processed bacon samples purchased from the Washington, DC, retail market have been periodically analyzed since 1971 for the presence of volatile N-nitrosamines in the fried product. During that time, a downward trend in the concentration of N-nitrosopyrrolidine has been observed, and between 1978 and 1980 it plateaued at 4-30 ppb, with an average of 11 ppb. A recent survey, however, indicates a change in this downward trend, with N-nitrosopyrrolidine found at levels ranging from 1 to 65 ppb, average 21 ppb. Volatile N-nitrosamines were found at levels up to 110 ppb in the fried product and up to 85 ppb in the fried-out bacon fat.     

Plant‐available nitrogen in the soil: Relationships between pre‐plant and pre‐sidedress nitrate tests for corn production

Corn (Zea mays L.) producers in the rainfed regions sometimes sidedress fertilizer N according to pre‐plant–nitrate test (PPNT) results based on the assumption that there is a linear relationship between pre‐sidedress nitrate test (PSNT) and the PPNT. There has been no report on such relationship in Ontario (Canada) and elsewhere in the nonirrigated corn‐growing regions. A field study was conducted near Ottawa, Canada for 7 y to (1) determine changes in soil available N from pre‐planting to shortly after the sidedress stage (late June) for corn and (2) establish a quantitative relationship between PPNT and PSNT. In each year, soil samples from fields of three to four plot experiments with different cropping histories, soil textures, and management levels, taken at 7 to 10 d intervals, and from on‐farm trials taken at pre‐planting and pre‐sidedress, were extracted with 2 M KCl. The concentrations of NO ‐N were determined colorimetrically. It was found that soil NO ‐N concentration of PSNT was a linear function of PPNT with an average slope of 1.7. However, the slope of the regression equations differed dramatically among cropping sequences, and to a lesser extent, soil textures. The NO ‐N concentration after planting to pre‐sidedress was influenced by air temperature and precipitation during this period of time. Both PPNT and PSNT positively correlated with corn‐grain yield. Our data suggest that cautions must be taken when deciding the rate of fertilizer N for sidedress application to corn based on PPNT test, especially under more humid northern climate conditions.     

Effects of nitrification inhibitors on denitrification of nitrate in soil

Summary The influence of 28 nitrification inhibitors on denitrification of nitrate in soil was studied by determining the effects of different amounts of each inhibitor on the amounts of nitrate lost and the amounts of nitrite, N₂O and N₂ produced when soil samples were incubated anaerobically after treatment with nitrate or with nitrate and mannitol. The inhibitors used included nitrapyrin (N-Serve), etridiazole (Dwell), potassium azide, 2-amino-4-chloro-6-methylpyrimidine (AM), sulfathiazole (ST), 4-amino-1,2,4-triazole(ATC),2,4-diamino-6-trichloromethyl-s-triazine (CL-1580), potassium ethylxanthate, guanylthiourea (ASU), 4-nitrobenzotrichloride, 4-mesylbenzotrichloride, sodium thiocarbonate (STC), phenylmercuric acetate (PMA), and dicyandiamide (DCD).Only one of the nitrification inhibitors studied (potassium azide) retarded denitrification when applied at the rate of 10 g g^–1 soil, and only two (potassium azide and 2,4-diamino-6-trichloromethyl-s-triazine) inhibited denitrification when applied at the rate of 50 g g^–1 soil. The other inhibitors either had no appreciable effect on denitrification, or enhanced denitrification, when applied at the rate of 10 or 50 g g^–1 soil, enhancement being most marked with 3-mercapto-1,2,4-triazole. Seven of the inhibitors (potassium azide, sulfathiazole, potassium ethylxanthate, sodium isopropylxanthate, 4-nitrobenzotrichloride, sodium thiocarbonate, and phenylmercuric acetate) retarded denitrification when applied at the rate of 50 g g^–1 soil to soil that had been amended with mannitol to promote microbial activity.Reports that nitrapyrin (N-Serve) and etridiazole (Dwell) inhibit denitrification when applied at rates as low as 0.5 g g^–1 soil could not be confirmed. No inhibition of denitrification was observed when these compounds were applied at the rate of 10 g g^–1 soil, and enhancement of denitrification was observed when they were applied at the rate of 50 or 100 g g^–1 soil.     

Specific ion effect on the accumulation of abscisic acid in wheat

Studies were carried out in the glass house using sand culture to find out the specific ion effect on the accumulation of abscisic acid in wheat. Seeds were sown in sixteen different solutions of chloride, sulphate, nitrate, carbonate salts of sodium, potassium, calcium and magnesium used each at ‐2 bar osmotic potential. The leaf samples taken after 25 days of sowing indicated that osmotic as well as salt stress increased significantly the accumulation of abscisic acid. The accumulation of abscisic acid was significantly less under potassium and calcium salt ions as compared to that under sodium and magnesium salts ions. Overall effect of anions showed that accumulation of abscisic acid was more under PEG (osmotic stress and chloride salts but it was less under sulphate and nitrate salts and was the least under carbonate salts. The accumulation of abscisic acid was exceptionally high under potassium dihydrogen phosphate. In general, the accumulation of abscisic acid‐a growth inhibitor varied not only with the type of the cation but also depended on the accompanying anion indicating differential growth response of plants under different types of saline conditions having dominance of different salt ion(s).     

Longevities and nitrogen,phosphorus, and potassium release patterns of polymer‐coated controlled‐release fertilizers at 30°C and 40°C

Abstract

The weekly nitrogen (N), phosphorus (P), and potassium (K) release from 17 polymer‐coated controlled‐release fertilizer (CRF) formulations of Nutricote, Apex Gold, Osmocote, and a 9‐month Macrocote were measured at 30.6±0.8°C and 40.0±1.5°C. Five grams of each CRF were placed at a depth of 50 mm in 280x50 mm acid washed then rinsed silica sand columns which were leached with deionized water three times each week until nutrient recovery ceased. The volume of leachate was recorded each week and subsampled for ammonium‐N, nitrate‐N, phosphate‐P, and K analyses. Each CRF treatment was replicated three times at each temperature. Nutrient release profiles were determined. Longevities, measured as weeks to 90% nutrient recovery, were considerably shorter than the nominated release periods for all formulations. Within each CRF product group, the longevity of 9 and 12 month formulations were similar with Apex Gold 12–14 month high nitrate having the longest (38 weeks for N at 30°C) and Osmocote 8–9 month the shortest (23 weeks for N at 30°C). There were consistent trends in the nutrient release periods across all CRFs with P>K>N and with differences of around 10% in duration between nutrients. The P:N release ratio exceeded 0.10 for most CRFs during the early release period indicating an adequate P supply for most plant species. The mean reduction in longevity for Nutricote, Apex Gold, and Osmocote formulations for an increase in incubation temperature from 30°C to 40°C was 19–21 % for N, 13–14% for P, and 14–15% for K. All CRFs released nutrients unevenly with the highest rate occurring during the early part of the release period. This pattern was accentuated at 40°C and by the shorter term release formulations. The nutrient release rates of all CRFs declined steadily after their maxima.     

Einfluß einer hohen Nitratdüngung auf Kinetik und Gaszusammensetzung der Denitrifikation in unterschiedlichen Böden

Effect of high nitrate application on the kinetic and gaseous composition of denitrification in different soils Kinetic and gaseous composition of denitrification were studied with 16 different soil horizons after application of a relatively high amount of nitrate (400 μg NO N/g dry soil) at defined conditions (He atmosphere; 80 % WHC; 30°C; 3 weeks). At the conditions given, denitrification followed zero-order kinetics depending on the amount of decomposable organic matter rather on than the nitrate concentration. Denitrification intensity was most significantly correlated with the amount of extractable or mineralizable organic carbon (C_H2O and C_min, respectively). N₂ and N₂O (but not NO) were liberated by all samples, the amount and ratio depending on the soil and time of sampling. At the end of the three week's incubation period, the N₂/N-N₂O ratio varied between 8.1 and 1.4/1 (with an average of 3.1/1), except for the acid Ah-sample of the Pararendzina (N₂/N-N₂O = 1.0/1.2). The incorporation of an excess of easily decomposable leaf-powder resulted in an increased nitrate turn-over (from 64.7 % to 95,7 % of the nitrate loss) with N₂ as the single denitrification product. N₂O could be detected only with the acid “B”-material of the Pararendzina. The denitrifying capacity Y (in μg N₂+N-N₂O/g soil) of a soil at the conditions given may be predicted by the amount of water-extractable organic carbon X (in μg C_H2O/g soil) according to the equation Y = 0.808 X + 120,1.     

Soil sample bag effects on pre‐sidedress soil nitrate test concentrations

Abstract

Most soil testing laboratories require soil samples collected for the pre‐sidedress soil nitrate test (PSNT) to be dried before shipment. Shipment of field‐moist samples would make it easier to use the test. The objective of this study was to measure the effect of bag type on changes in soil nitrate in samples collected for the PSNT. Soil samples were collected from the surface foot of soil when corn (Zea mays L.) plants were 15‐ to 30‐cm tall. Four fields with a history of manure applications were sampled. The bulk sample was subsampled in the field and the subsamples were kept cool during transport to the laboratory and were immediately air dried after arrival at the laboratory. Field‐moist subsamples from each bulk sample were placed into either cloth bags or plastic‐lined paper bags after arrival at the laboratory. Four replications of the subsamples were incubated at 30°C for 1, 2, 3, and 4 days. After removal from the incubator, the subsamples were immediately spread to air dry. The soils incubated in the plastic‐lined paper bags did not significantly increase in nitrate after one day of incubation. There was a significant increase, however, in nitrate each day after the second, third and fourth day of incubation. The soils incubated in the cloth bags did not significantly increase in nitrate until the fourth day of incubation. The average increase in nitrate‐N concentration in the cloth bags between day 3 and day 4 was 1.5 mg kg L^‐1soil. The results suggest that cloth bags could be used to ship field‐moist soil samples for the PSNT without significant changes in soil nitrate concentrations.     

Simultaneous automated determination of chloride,nitrite, nitrate,and ammonia in water and wastewater

An automated system capable of simultaneous determination of chloride, nitrite, nitrate, and ammonia in about 2 ml of fresh water or wastewater is described. The four compounds are determined using modifications of established colorimetric procedures. Results can be reported at a true rate of five samples per hour with a relative standard deviation at optimum concentrations of less than 2%. Detection limits are 1 ppm Cl for chloride and 1, 5, and 5 ppb N for nitrite, nitrate, and ammonia, respectively. Sample pH adjustment is not required from 0.0002 N H₂SO₄ (pH 3.7) to 0.005 N NaOH (pH 11.2). Fresh water and wastewater samples were analyzed for nitrite and ammonia by the proposed procedure and by the manual sulfanilic-naphthylamine and nesslerization method. Analysis by the student t-test showed no significant difference between the paired sets of data (P > 0.5). When potable and wastewater samples were spiked with sodium chloride, potassium nitrate, sodium nitrite, and ammonium chloride and analyzed, average recoveries were 99 to 103%.     

Effects of Broad-Leaf Crop Frequency in Various Rotations on Nitrate Nitrogen and Extractable Phosphorus in a Black Chernozem Soil

In the Canadian prairies, current recommendations allow growing of canola or pea once every 4 years on a particular field to effectively mange diseases, insects, and weeds, but producers are interested in increasing frequency of these crops to optimize economic returns. A 4-year (from 1999 and 2002) field experiment, with treatments consisting of rotations of monoculture canola and pea to rotations that contained these crops every 2, 3, and 4 years with wheat and flax, was conducted on a Black Chernozem (Udic Boroll) silty clay at Melfort, Saskatchewan, to determine the impact of frequency of broad-leaf crops canola and pea in various crop rotations on accumulation and distribution of nitrate nitrogen (N) and extractable phosphorus (P) in the soil profile after 4 years. Two cultivars of canola, an herbicide-tolerant blackleg- resistant variety (hybrid) and a conventional (not herbicide tolerant) open-pollinated, blackleg-susceptible variety (OP), were included. Mean effects of crop rotation or rotation length on soil nitrate N were not significant, though the amount of soil nitrate N in different soil layers tended to be greatest with monocultures and least in the 4-year rotation with flax. Effects of crop phase (i.e., individual crops that make up the rotation)?×?crop rotation interactions on soil nitrate N were significant for all layers in the soil profile. The amounts of nitrate N in soil after canola, especially hybrid canola, were lowest in most crop rotations, suggesting the importance of canola in minimizing downward movement of nitrate N in the soil profile. Soil extractable P in the 0- to 15-cm layer was least with monocultures and greatest in the 4-year rotation with flax. There was a significant effect of crop phase on soil extractable P, but soil P levels varied with crop phase in different rotations. In conclusion, residual nitrate N in soil can be reduced by extending crop rotations and using high-yielding disease-resistant canola cultivars, most likely by improving crop yields.     

MANAGEMENT OF UREA-CONTAINING FERTILIZERS FOR NO-TILLAGE CORN USING NITROGEN STABILIZERS AND COATED-GRANULE TECHNOLOGY

No-tillage production systems are being used by an increasing number of producers in the Great Plains, however, the large amount of surface residue left on the soil surface can made nitrogen (N) management difficult. There are several products currently available for use with granular urea (46% N) and urea-ammonium nitrate solution (UAN) that have the ability to reduce or eliminated N losses. The objective of this study was to evaluate the effectiveness of several N-fertilizer additives and a slow-release polymer coated urea product in a no-tillage corn (Zea mays L.) production system. A 3-year field experiment was conducted from 2006–2008 at the North Central Kansas Experiment Field, located near Scandia, KS, on a Crete silt loam soil (fine, montmorillonitic, mesic Pachic Arquistoll). When averaged over the 3-years of the experiment, the treated fertilizer products yielded greater than untreated urea or UAN. This occurred regardless of applied N-rate. The additive treated products along with the time release-polymer coated urea yield the same as ammonium nitrate. There were no significant differences among additive products. If producers wish to broadcast urea-containing N-fertilizer on the soil surface in high-residue production systems there are several N- additive options available that limit N loses and maximize grain yield with reduced environmental risk     

Spinach (Spinacia oleracea) powder as a natural food-grade antioxidant in deep-fat-fried products

The addition of spinach (Spinacia oleracea) powder in flour dough as a natural antioxidant was investigated, and oxidation of frying oil and the lipid in fried products during frying was also studied. Flour dough with spinach powder was rolled into sheets of 0.1 cm thickness and then cut into squares to be fried. Each frying was performed in 160 degrees C soybean oil for 1 min, repeated every 20 min for 20 h. Fried samples were analyzed immediately or after being stored at 60 degrees C for 12 days under dark. The lipid content of fried dough was lower in samples with the addition of spinach powder. Spinach in the dough decreased accumulation of the polar compounds in soybean oil during frying but had little effect on the fried dough. It also reduced conjugated diene and aldehyde formation in the lipid of fried dough during storage. Improvement in lipid oxidative stability, presumably due to pigments in spinach, was more noticeable in the fried products during storage than in the frying oil.     

Evaluation of analysis of polycyclic aromatic hydrocarbons by the QuEChERS method and gas chromatography-mass spectrometry and their formation in poultry meat as affected by marinating and frying

The objectives of this research were to develop a method for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in poultry meat by combining the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method with gas chromatography-mass spectrometry (GC-MS) and study their formation during marinating and frying. The recoveries of 16 PAHs ranged from 94.5 to 104% in blank samples and from 71.2 to 104% in poultry meat samples. The quantitation limits of 16 PAHs were from 0.02 to 1 ng/mL, with the intraday variability being from 2.4 to 6.6% [percent relative standard deviation (RSD%)] and interday variability being from 3.3 to 7.1% (RSD%). Most PAHs followed a time-dependent increase over a 24 h marinating period, with naphthalene being generated in the largest amount. Among the various poultry meat, chicken gizzard produced the highest level of total PAHs after 24 h of marinating. A similar tendency was observed for most PAHs during frying of poultry meat, but a high amount of total PAHs was shown in duck drumstick after 15 min of frying.     

Comparison of three methods for determination of N-nitrosopyrrolidine in fried dry-cured and pump-cured bacon

Three methods, the mineral oil distillation (MOD), the dry column (DC), and a low temperature vacuum distillation (LTVD), for the determination of N-nitrosopyrrolidine in dry-cured and pump-cured bacon were compared. Each method uses the thermal energy analyzer for the determinative step. The coefficients of variation for repeatability were 10.3% (MOD), 7.2% (DC), and 9.1% (LTVD) for the dry-cured bacon study and 8.7% (MOD), 8.5% (DC), and 7.1% (LTVD) for the pump-cured bacon study. The pooled coefficients of variation for between-method reproducibility were 11.8% for the dry-cured bacon and 10.8% for the pump-cured bacon. The pooled coefficients of variation for repeatability were 9.0% for the dry-cured bacon and 8.2% for the pump-cured bacon. These values compare favorably with the values from previous collaborative or validation studies of the individual methods, and the methods can be considered to be equivalent.