Volatile, non-volatile and total N-nitroso compounds in bacon.

Twenty-five smoked and unsmoked fried bacon samples have been analysed by a group selective procedure to measure the concentration of apparent total N-nitroso compounds (ATNC). The levels of a range of individual N-nitroso compounds, including simple volatile N-nitrosamines, N-nitrosothiazolidines, N-nitrosamino acids and N-nitrosothiazolidine carboxylic acids have also been examined. Concentrations of ATNC varied from 430 to 6800 micrograms(N-NO)/kg with a mean of 2700 micrograms(N-NO)/kg. Protein-bound N-nitrosoproline was the most abundant compound detected in unsmoked bacon, mean 260 micrograms/kg, and on average accounted for 4% of the ATNC concentration. For smoked bacon, bound N-nitrosoproline was detected in levels of up to 890 micrograms/kg and contributed 5% to the ATNC total. The most abundant compound present in smoked bacon was N-nitrosothiazolidine-4-carboxylic acid, mean 660 micrograms/kg, and this accounted for 6% of the ATNC. N-Nitrosothiazolidine, mean 340 micrograms/kg, and 2-(hydroxymethyl)-3-nitrosothiazolidine-4-carboxylic acid, mean 180 micrograms/kg, were the next most prominent compounds detected in smoked bacon. The combined sum of all the individual N-nitroso compounds measured accounted for, on average, 16% of the total ATNC. The identities of the N-nitroso compounds comprising the majority of the ATNC in bacon remain unknown.     

Surveillance of preservatives and their interactions in foodstuffs.

The organization of food surveillance in the UK is described, in particular as it has been applied to preservatives and their interaction products in foods. Applications of nitrates and nitrites as preservatives are discussed, together with the consequential exposure of consumers to these anions and their reaction products. Analytical methods for the determination of volatile and non-volatile N-nitroso compounds are referred to in relation to the results in food surveillance studies. Concentrations of Apparent Total N-nitroso Compounds (ATNC) averaged 2900 micrograms(N-NO)/kg in fried smoked bacon compared with 2400 micrograms/kg in fried unsmoked bacon; of this, known volatile and non-volatile N-nitroso compounds accounted for only 10-20%. ATNC were not detected in cheeses except those manufactured with added nitrate when ATNC levels up to 210 micrograms(N-NO)/kg were detected. Further studies are needed to determine the identity and toxicological properties of the non-volatile N-nitroso compounds.     

Examination of some fermented foods for the presence of apparent total N-nitroso compounds

The fermented foods yoghurt, bread and cheese were analysed for the presence of apparent total N-nitroso compounds (ATNC) by a group-selective procedure involving direct chemical denitrosation and chemiluminescence detection of the released nitric oxide. The levels of ATNC were below the 20 micrograms(N-NO)/kg detection limit in all 20 yoghurts, 23 of the 24 bread samples and 28 out of 31 different varieties of cheese analysed. ATNC were detected in most of those cheese samples manufactured with added nitrate, including Edam, Gouda and Havarti, in concentrations ranging from 30 to 210 micrograms(N-NO)/kg.     

An investigation of the levels of N-nitrosodimethylamine, apparent total N-nitroso compounds and nitrate in beer

Over 170 retail samples of beer have been analysed for N-nitrosodimethylamine (NDMA), apparent total N-nitroso compounds (ATNC) and nitrate. Levels of NDMA ranged from below 0.1 up to 1.2 micrograms/kg with a mean of 0.2 micrograms/kg. ATNC was detected in 42% of the samples in concentrations of up to 569 micrograms (N-NO)/kg. The levels of nitrate ranged from less than 0.2 up to 143 mg/kg with a mean of 16.8 mg/kg. There was no correlation between the amounts of NDMA and ATNC found in the retail beers. Samples taken during the course of fermentation showed that NDMA was unaffected by the bacterial reduction of nitrate which causes ATNC formation. HPLC studies using a photolysis/chemiluminescence detector revealed that the ATNC in beer are highly polar species of as yet unknown identity.     

Some nitrosoamino acids in bacon adipose tissue and their contribution to the total N-nitroso compound concentration

The levels of nitrosoamino acids and apparent total N-nitroso compounds in the adipose tissue of raw bacon have been examined. Nitrosoamino acids were detected in 80% of the samples in levels of up to 0.2 mg/kg. Apparent total N-nitroso compounds were present in all samples in concentrations of between 0.4 and 3.7 mg (N-NO)/kg. Nitrosoamino acids accounted for approximately only 1% of the apparent total N-nitroso compounds. The majority of the apparent total N-nitroso compounds in the adipose tissue were associated with the insoluble connective tissue fraction, with the remainder present as chloroform soluble species.     

Some nitrosoamino acids in bacon adipose tissue and their contribution to the total N-nitroso compound concentration

Zusammenfassung Der Gehalt an Nitrosoaminosäuren und ihr Anteil an den Gesamt-N-Nitrosoverbindungen im Fettgewebe von rohem Schinkenspeck wurde untersucht. In 80% der Proben wurde ein Gehalt an Nitrosoaminosäuren von bis zu 0,2 mg/kg festgestellt. Scheinbare Gesamt-N-Nitrosoverbindungen waren in allen Proben in einer Konzentration von 0,4 bis 3,7 mg (N-NO)/kg vorhanden. Die eigentlichen Nitrosoaminosäuren machen nur etwa 1% der scheinbaren Gesamt-N-Nitrosoverbindungen aus. Die Mehrzahl der scheinbaren Gesamt-N-Nitrosoverbindungen im Fettgewebe findet sich im nichtlöslichen Bindegewebe, wobei der verbleibende Rest chloroformlöslich ist.Summary The levels of nitrosoamino acids and apparent total N-nitroso compounds in the adipose tissue of raw bacon have been examined. Nitrosoamino acids were detected in 80% of the samples in levels of up to 0.2 mg/kg. Apparent total N-nitroso compounds were present in all samples in concentrations of between 0.4 and 3.7 mg (N-NO)/kg. Nitrosoamino acids accounted for approximately only 1 % of the apparent total N-nitroso compounds. The majority of the apparent total N-nitroso compounds in the adipose tissue were associated with the insoluble connective tissue fraction, with the remainder present as chloroform soluble species.

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Einige Nitrosoaminosäuren im fettgewebe von Schinkenspeck und ihr anteil an der Konzentration der Gesamt-N-Nitrosoverbindungen

     

Nitrate, nitrite, and N-nitroso compounds in Finnish foods and the estimation of the dietary intakes

An estimate of the dietary intakes of nitrite, nitrate and N-nitroso compounds is presented, based on the analytical data supplied by the Finnish Food Quality Control. Figures on the food consumption of the Finnish population, taken from a national dietary survey, and food consumption of 1768 children and adolescents over a 48-h recall period were used. The mean daily dietary nitrate intakes were estimated to be about 55 mg for the total population and for children and adolescents. The mean nitrite intakes were 1.88 mg for the total population and 1.07 mg for children and adolescents. The intake of N-nitroso compounds (NDMA) was estimated to be 0.08 micrograms for the total population and 0.02 micrograms for children. Nitrates were found to originate mainly from vegetables (80%), nitrites from meat products (97%) and nitrosamines mostly from fish products and beer. A comparison of the estimate of dietary intake of with ADI values indicated that the nitrite intake of the total population was 23% and by children 39% of ADI. The average weight was approximately 60 kg for adults and 20 kg for children. When measured average weight (39 kg) was used, and the nitrite intake was found to be 28% of ADI. Nitrate intakes from food additives were 2.5% and 1.4% of the ADI value, respectively. When the total nitrate intake from various food sources was compared with the ADI (which is given only for food additives), the estimated nitrate intake of the total population was 25% and that of children 28% of the ADI value.     

A method for the investigation of free and protein-bound N-nitrosoproline in beer

Hydrolysis of beer peptides and proteins by both mild enzymatic and vigorous alkaline conditions has established that peptide-bound N-nitrosoproline residues are not present in beer in significant quantities. Free N-nitrosoproline remains the single most abundant identified N-nitroso compound, and this accounts for up to 10% of the apparent total N-nitroso compounds (ATNC). Both hydrolysis and extractability studies strongly indicate that the majority of the ATNC are not associated with beer peptides, but rather are likely to be low molecular weight possessing in some cases an acidic functional group.     

Incidence of some non-volatile N-nitroso compounds in cured meats

Procedures are described for the use of high-performance liquid chromatography and gas chromatography with a chemiluminescence detector in the analysis of N-nitrosoamino acids, N-nitrosothiazolidine-4-carboxylic acid, N-nitroso-oxazolidine-4-carboxylic acids and N-nitroso dipeptides N-terminal in N-nitrosoproline in cured meat products. The detection limit is around 5-10 micrograms/kg. Evidence is presented for the presence of all these species except the N-nitrosated dipeptides.     

DEVELOPMENT OF METHODS FOR THE CHARACTERISATION OF NON-VOLATILE N-NITROSO COMPOUNDS IN MALT

The effect of pH on extractability and the chromatographic separation of non-volatile N-nitroso compounds in aqueous wort extracts of malt have been studied. The apparent total N-nitroso compounds (ATNC) contain acidic functional groups and consist of a large number of minor components.     

麦芽和啤酒中的N-亚硝基化合物

N-亚硝基化合物属强致癌物质,有挥发性N-亚硝基二甲胺（NDMA）和非挥发性N-亚硝基化合物（ATNC）两种。啤酒中的NDMA主要来源于麦芽,在制麦工艺过程中形成;ATNC主要由微生物的硝酸还原反应产生。啤酒中的N-亚硝基化合物的分析检测方法有热能分析仪法、气相色谱法和HPLC法。（孙悟）     

AN INVESTIGATION INTO THE APPARENT TOTAL N-NITROSO COMPOUNDS IN MALTS

The levels of apparent total N-nitroso compounds in a range of UK malts have been investigated, and the effects of various kilning procedures are reported. Concentrations of N-nitrosodimethylamine and N-nitrosoproline have been determined for selected malts kilned with and without sulphuring. Low or non-detectable levels of apparent total N-nitroso compounds are consistently found only in malts kilned under low NOX conditions. Sulphuring appreciably reduces N-nitrosodimethylamine but has little effect on production of the majority of non-volatile N-nitroso compounds.     

Formation and occurrence of cancer-producing hydrocarbons in cereals and possibilities for their reduction

According to the authors' investigations every inhabitant of the GDR takes between 0.2 and 1.0 mg BaP. per year by food consumption including amounts of 0.03 to 0.17 mg on account of cereals and mill products. For the contamination of cereals the following sources are in consideration: environmental contamination on account of industry dust (distant from industry 0.1 to 0.6, near to industry 0.3 to 4.2 micrograms BaP/kg), passing over from soil to plant (with model experiments with soils more than 10 000 micrograms BaP/kg up to 22.3 micrograms BaP/kg dry matter) as well as technologically caused contamination for instance by direct fume-and-gas drying (with the use of raw lignite up to 10 micrograms BaP/kg). As it can be concluded from model experiments BaP passes to flour at milling in dependence of the extraction rate. By separating the husks prior to milling more than 50% of BaP can be removed from the stock.     

Review of methodologies for the determination of nonvolatile N-nitroso compounds in foods

An attempt has been made to briefly review methods available for the determination of total N-nitroso compounds, N-nitrosamides, N-nitrosamino acids, and miscellaneous other nonvolatile N-nitroso compounds in foods and beverages, giving special emphasis to the progress made during the past five years. It appears that a wide variety of acceptable methods are available for N-nitrosamino acids and simple hydroxylated N-nitrosamines, but none of them has yet been adequately validated. Only limited progress has been made for the analysis of N-nitrosamides, N-nitroso sugar amino acids, and other N-nitroso compounds. Various mass spectrometric methods available for the determination and confirmation of these compounds are also discussed.     

Review of the occurrence and formation of non-volatile N-nitroso compounds in foods.

A review of the literature published prior to July 1991 covers the occurrence and formation of non-volatile N-nitrosamines occurring in foods and beverages. The presence of identified volatile and non-volatile N-nitrosamines accounts for less than 10% of the total apparent N-nitrosamine concentration. N-Nitrosoproline and N-nitrosothiazolidine-4-carboxylic acid are the most commonly identified non-volatile N-nitrosamines in the diet. Non-volatile N-nitrosamines account for 12 of the 21 currently identified N-nitroso compounds in foods and beverages.     

N-nitrosamines and residual nitrite in cured meats from the Dutch market

A total of 140 samples of 16 kinds of cured meats were analyzed for contents of residual nitrite and N-nitrosamines. Nitrite was determined by reaction with sulfanilamide/naphthylethylenediamine and colorimetric measurement. N-nitrosamines were isolated from the samples by vacuum distillation and determined by gas-chromatography with chemiluminescence detection (GC-TEA). In six samples no nitrite was detectable (less than 1 mg NaNO2/kg), the remaining samples contained 1-140 mg NaNO2/kg, median value 6.8 mg/kg. In 46 samples (33%) no N-nitrosamines were detected, i.e. less than 0.1-0.5 microgram/kg of the individual nitrosamines, depending upon their structure. N-nitrosodimethylamine (NDMA) was the nitrosamine present most frequently, in 75 samples, contents were 0.1-0.9 microgram/kg, mean 0.3 microgram/kg. Other N-nitrosamines found were: N-nitrosopiperidine (NPIP), 10 times, 0.3-25 micrograms/kg; N-nitrosodiethylamine (NDEA), three times, 0.2-0.9 microgram/kg; N-nitrosopyrrolidine (NPYR), three times, 1.3-4.2 micrograms/kg; N-nitrosomorpholine, once, 0.7 microgram/kg and N-nitrosothiazolidine (NTHZ), 36 times, 0.5-91 micrograms/kg, mean 5.7 micrograms/kg. NTHZ was found most often and with the highest contents in smoked products. Frying of bacon and cured, smoked pork bellies led to substantially increased levels of NPYR in both products, and for the pork bellies also of NTHZ. In five samples of cured, smoked pork bellies after frying NTHZ-contents of 3.6-490 micrograms/kg (mean 179) were found. No correlation between residual nitrite levels and N-nitrosamine contents could be established. Investigations during the nineteen seventies gave much higher levels for NDMA, NDEA, NPIP and NPYR in Dutch cured meats than now found; at that time NTHZ was not measured.     

Lead contamination during domestic preparation and cooking of potatoes and leaching of bone-derived lead on roasting, marinading and boiling beef.

Lead concentrations were measured in boiled, mashed potatoes and in baked potatoes that had been prepared and cooked in domestic kitchens. Levels of lead in the boiled, mashed potatoes ranged from below the 1 microgram/kg limit of detection up to 18 micrograms/kg with a mean of 6 micrograms/kg (wet weight). In the large majority of cases the lead in the tap water was the predominant source of the metal. Higher amounts of lead (range 11 micrograms/kg to 56 micrograms/kg, mean 27 micrograms/kg) were present in baked potatoes and this was attributed to soil adhering to the potato skin. The extent of leaching of lead from bone during cooking has also been investigated. For beef stocks there was little evidence to suggest that significant migration of bone lead occurred. For beef casseroles, marinaded in red wine, some leaching did occur from beef joints containing elevated amounts of bone lead; however the levels were all below 350 micrograms/kg and, on average, less than double that found in casseroles prepared from normal joints where the bone lead levels were an order of magnitude less.     

固相萃取净化-高效液相色谱法测定肉制品中的9 种N-亚硝基化合物

建立采用固相萃取-高效液相色谱法同时测定肉制品中9 种N-亚硝基化合物的方法。以甲醇为提取剂,60 ℃条件下超声提取,经CNWBOND HC-C18固相萃取柱净化后,采用AQ-C18色谱柱分析。甲醇和超纯水为流动相实现了待测物的良好分离,紫外检测器检测,结合保留时间和光谱图定性,外标法定量。结果表明：9 种N-亚硝基化合物线性关系良好,相关系数均大于0.99;方法定量限（RSN = 10）为0.047～0.097 μg/g;回收率为72.6%～97.6%;相对标准偏差（n＝6）为3.1%～7.9%。此方法前处理简单、回收率高、精密度好,适用于肉制品中9 种N-亚硝基化合物的同时测定。     

鱼露及加工技术研究进展

介绍了鱼露发酵生产的基本情况,并从安全性、生物活性、风味以及快速发酵生产工艺4个方面说明发酵法生产鱼露的研究进展;特别说明了鱼露中存在致癌性前体成分———亚硝基化合物以及多种生物活性成分;介绍了目前对鱼露中挥发性成分和非挥性成分风味成分的鉴定研究情况,指出了快速发酵工艺给鱼露风味带来的负面影响。     

Influence of nitrate, ascorbic acid, and nitrate reductase microorganisms on N-nitrosamine formation during Korean-style soysauce fermentation.

Traditional Korean soysauce samples were collected from households in Chinju, Gyeongnam, Korea and analysed for volatile N-nitrosamines. Five of 24 samples contained NDMA (range = 1.6-10.4 micrograms/l) which was the only volatile N-nitroso compound found. Soysauce made from well water contained NDMA more often (4 of 6 samples) than soysauce made from tap water (1 of 18). This suggests that the water source is a determinate in the NDMA content of soysauce, probably due to a higher nitrate content of well water. The source of salt used did not clearly influence NDMA content. Soysauce was prepared in the laboratory using traditional methods but with 0 to 400 mg/l nitrate and in some cases made 6.5 to 65 mM in ascorbic acid and fermented for 120 days. The NDMA content of the samples was positively correlated with increasing nitrate concentration. Nitrate at 400 mg/l resulted in an NDMA content of 203 micrograms/l. Ascorbic acid substantially inhibited NDMA formation. All samples contained large numbers of nitrate reductase-containing organisms (greater than 1 x 10(7) CFU/ml).