Effects of Frying Procedures and Compositional Factors on the Temperature Profile of Bacon

The effects of frying procedures (preheated vs cold skillet) and compositional factors (adipose vs lean) on the final temperatures attained in fried bacon were investigated as a prelude to studying the kinetics of N-nitrosopyrrolidine formation in bacon. With a preheated skillet set at 171°C, the final temperature reached in whole bacon samples at the end of the 6 min frying time was 164 ± 3°C. Bacon samples, initially placed in a cold skillet preset to heat to 171°C, attained temperatures of 127 ± 5°C and 165 ± 6°C at the end of 6 and 8 min frying periods, respectively. It was observed that the lean bacon strips rarely exceeded 145°C while the adipose approached 165°C when separated adipose and lean components from whole bacon samples were fried for 6 min in a preheated (171°C) skillet.     

Inhibition of N-Nitrosamine Formation in a Cured Ground Pork Belly Model System

A model system consisting of a uniformly distributed sample of ground pork in conjunction with a nitrite containing curing solution was utilized to evaluate the formation of N-nitrosamines. Utilizing this system a wide variety of compounds were discovered to dramatically reduce the level of N-nitrosopyrrolidine (NPyr) formed during frying. Carbohydrates including the reducing sugars dextrose, ribose, lactose, and maltose, as well as liquid smoke preparations, were found to reduce NPyr levels by as much as 60%. In addition, when low levels of combinations of inhibitors glucose, liquid smoke, and α-tocopherol were incorporated, reductions in nitrosamine levels as great as 80% were observed in model systems as well as in pilot plant manufactured bacon.     

The effect of antioxidants on the production of volatile nitrosamines during the frying of bacon.

In model system studies simulating the frying of bacon a considerable variation in the production of N-nitrosopyrrolidine (NOPyr) has been observed, as occurs in sliced bacon fried conventionally. The inclusion of ascorbate or erythorbate (isoacorbate) has led consistently to a fall in or an elimination of NOPyr production up to an addition of 300 ppm (1,5 mM). Above this concentration of ascorbate, the elimination of NOPyr formation persisted in some instances but in others an increased production of the nitrosamine occurred. Using alpha-tocopherol, a fall of NOPyr production during the simulated frying of bacon was obtained with increase of concentration of the antioxidant, there being a consistent elimination of the volatile nitrosamine following an additionof 500 ppm (1.16 mM). Whilst ascorbyl palmitate had a similar action in reducing or eliminating NOPyr production, no synergistic effect between it and alpha-tocopherol was noted in an experiment combining the two antioxidants. When bacon was fried in fat containing 400 or 800 ppm alpha-tocopherol, the total production of NOPyr and DMN in the fried bacon, cooked out fat and condensate was markedly reduced but not completely eliminated as in the model system studies. Similarly, the curing of bacon with a brine containing a mixture of alpha-tocopherol, ascorbyl palmitate and citric acid has led to considerable reductions in NOPyr and DMN output on frying when the combined concentrations of the two anti-oxidants were calculated to be 800 ppm.     

N-Nitrosothiazolidine and N-Nitrosothiazolidine-4-Carboxylic Acid in Smoked Meats and Fish

Various smoked meats including raw and fried bacon and both unsmoked and smoked (uncured) fish were analyzed for NThZ and NTCA. Most meat samples, bacons, and a few smoked fish contained traces of NThZ and considerably high (up to 13,700 ppb) levels of NTCA. Preliminary results indicated that raw bacons processed by old-fashioned direct smoking methods contained the highest (> 1,000 ppb) level of NTCA. Formation of NThZ from the NTCA present in smoked bacon increased with an increase in frying temperature as well as with frying time. NTCA level in the raw bacon and the cooking conditions seemed to be the most important factors involved in the formation of NThZ in the fried bacon. The reason for finding only insignificant levels of NThZ in smoked fish could not be established conclusively.     

基于均匀设计和主成分分析的甘薯薯片油炸工艺优化

为优化甘薯薯片油炸工艺,采用单因素和均匀设计相结合进行试验,对均匀设计试验数据进行多元回归分析。单因素试验表明:切片厚度、预干燥阶段和油炸阶段对含油量、L*值和b*值有较大影响;均匀设计逐步回归分析表明:油炸时间对含油量影响显著(P=0.011),食盐水质量分数对含水量影响显著(P=0.022),油炸温度和油炸时间对L*值影响极显著(P=0.001),预干燥时间和油炸时间对b*值影响显著,食盐水浸泡时间、食盐水质量分数、预干燥温度、预干燥时间和切片厚度对脆度的影响符合二次多项式回归模型(P=0.001);指标主成分分析表明:提取2个主成分能解释87.4%的指标信息,达到指标降维目的;岭回归分析建立了综合得分回归模型,相关系数R为0.997,能很好地拟合产品的综合得分;偏最小二乘法回归分析预测最佳综合评分工艺参数为切片厚度2 mm、热烫时间1 min、质量分数1%食盐水浸泡20 min、预干燥温度60℃、预干燥时间70 min、油炸温度150℃、油炸时间1 min,验证综合评分为0.89,综合评分高于均匀设计试验组最高值0.86。优化工艺所得产品具有含油量低、颜色和脆度俱佳等特点,相关模型具有良好的预测能力。     

Effect of d1-α-Tocopherol on Antibotulinal Effectiveness of Sodium Nitrite in Bacon

It has been proposed that d1-α-tocopherol be added to bacon to reduce the formation of nitrosamines upon frying. The effect of d1-α-tocopherol on antibotulinal properties of bacon formulated with sodium nitrite was tested. The bacon was made with 0 or 0.9% sucrose and 0, 500 or 1,000 ppm d1-α-tocopherol. Each slice was inoculated with heat-shocked spores of Clostridium botulinum types A and B, then incubated at 27, 25 or 23°C in vacuum packages. Gassy samples were assayed for botulinum toxin as they occurred. The addition of d1-α-tocopherol up to 1,000 ppm did not retard the antibotulinal properties of 120 ppm sodium nitrite in bacon.     

EFFECT OF FRYING AND OTHER COOKING CONDITIONS ON NITROSOPYRROLIDINE FORMATION IN BACON

Nitrosopyrrolidine (NO-Pyr) formation in bacon is primarily dependent on frying temperature and not time. Cooking methods affect the amount of NO-Pyr formed: pan frying produces the highest level of NO-Pyr with variable concentrations formed on baking, broiling and cooking in a "baconer." Microwave oven treatment produced the lowest amount of NO-Pyr. A model system study of the decarboxylation of nitrosoproline shows this precursor, which may be present in bacon, is maximally converted to NO-Pyr at 185°C near the recommended temperature for frying.     

复合香辛料亚硝化抑制剂对西式培根品质的影响

研究对N-亚硝胺具有阻断作用的复合香辛料亚硝化抑制剂（composite spice nitrosation inhibitor,CSNI） 在西式培根中的应用效果。设计4 组实验：1）阴性对照（negative control,NC）组：以原料肉质量计,配 制由0.06%亚硝酸钠、9%食盐、1.5%复合磷酸盐、5%白糖等组成的腌制液,注射量为20%;2）阳性对照 （positive control,PC）组：在NC组基础上添加0.055%异抗坏血酸钠;3）CSNI组：在NC组中添加CSNI; 4）PC＋CSNI组：在PC组中添加CSNI。制成西式培根,分别对西式培根成品和烧烤（200 ℃,5 min）西式培根进 行感官评定、pH值、红度值（a*）、硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARs）值、亚 硝酸盐残留量、生物胺含量及N-亚硝胺含量测定。结果表明：相比NC、PC组,PC＋CSNI组西式培根成品的感官 评分最高,TBARs值（0.24 mg/kg）、亚硝酸盐残留量（20.48 mg/kg）和生物胺总量（184.68 mg/kg）均处于较低 水平,CSNI对N-亚硝胺的形成（总量为9.29 μg/kg）,特别是N-二甲基亚硝胺的形成有显著的阻断效果,且CSNI的 添加对产品的pH值和a*均未造成显著影响;西式培根烧烤后,由于水分和脂肪溶出,致使烧烤西式培根的亚硝酸 盐残留量、生物胺含量和N-亚硝胺含量总体呈升高趋势,但均未超过相关规定的限量值。     

Volatile nitrosamines in microwave-cooked bacon

Bacon was analysed for volatile nitrosamines after microwave cooking, and the results were compared with those obtained after frying bacon in a pan. Microwave cooking gave statistically significantly lower levels of all three volatile nitrosamines detected in the bacon. NPYR was found in all 20 samples fried in a pan, but in only five microwave-cooked samples. The average volatile nitrosamine levels (micrograms/kg) in microwave-cooked bacon and pan-fried bacon were: NDMA, 0.3 and 1.2; NPIP, 0.04 and 0.2; NPYR, 0.1 and 4.5.     

重组培根加工过程中N-亚硝胺及其前体物质含量的动态变化

为了明确重组培根加工过程中N-亚硝胺含量的动态变化及其影响因素,监测原料肉、腌制、蒸煮、烟熏加工环节中pH值及亚硝酸盐、生物胺、N-亚硝胺含量的动态变化,同时考察重组培根的感官品质。结果表明：随着加工的进行,重组培根pH值和亚硝酸盐残留量均呈现先上升后下降的趋势;在监测的8 种生物胺中,原料肉中仅检出精胺,随着重组培根加工的进行,生物胺的种类不断丰富,含量逐渐升高,烟熏显著加速了生物胺的生成;原料肉中仅检测出N-二甲基亚硝胺（N-nitrosodimethylamine,NDMA）和N-亚硝基吡咯烷（N-nitrosopyrrolidin,NPYR）;腌制后可检出N-甲基乙基亚硝胺（N-nitrosomethylethylamine,NMEA）、N-二丙基亚硝胺（N-nitrosodipropylamine,NDPA）、N-二丁基亚硝胺（N-nitrosodibutylamide,NDBA）和N-亚硝基哌啶（N-nitrosopiperidine,NPIP）,NDMA含量超过了国标限量; 蒸煮后新增N - 二乙基亚硝胺（ N - n i t r o s o d i e t h y l a m i n e ,NDEA）和N-亚硝基吗啉（N- n i trosomorpholine,NMOR）,且NDMA、NDPA、NDBA、NPIP含量显著升高（P＜0.05）;烟熏过程中N-亚硝胺总量显著增加（P＜0.05）,烟熏6～9 h增幅最大;重组培根的感官评分随着烟熏时间的延长显著提高（P＜0.05）。综合食用安全性和感官评分,建议制作重组培根时选择腌制16 h,热熏法（55±2） ℃烟熏6h。     

An Investigation into Glucose as a Potential Precursor of N-Nitrosothiazolidine in Bacon

The possible involvement of glucose in the formation of N-nitrosothiazolidine (NTHZ) in bacon was investigated by pumping pork bellies with brines containing added glucose (2 and 4%). Raw bacon samples processed with glucose had significantly lower levels of N-nitrosothiazolidine-4-carboxylic acid than the smoked control bacons. When the bacon samples with glucose were fried for 6 and 12 min, no NTHZ was detected in the fried products. N-Nitrosopyrrolidine (NPYR) levels in these samples were much lower than those in the fried control samples. Results of this study demonstrate that the contribution of glucose to NTHZ formation in bacon is minimal relative to that of formaldehyde in the wood smoke.     

Factors Affecting the N-Nitrosothiazolidine Content of Bacon

The analysis of raw and cooked bacon for the presence of N-nitrosothiazolidine (NTHZ), a recently identified nitrosamine in bacon, indicated that the levels found were unrelated to residual nitrite or refrigerated storage. Raw bacon contained higher levels of NTHZ than either fried, baked, or broiled bacon. Since the total amount of NTHZ in whole raw bacon was higher than that found in fried bacon and its drippings combined, it was concluded that NTHZ was not formed during frying as is N-nitrosopyrrolidine. The presence of NTHZ in bacon appears to be associated with smokehouse processing.     

Reduction of Mutagen Formation in Cooked Nitrite-Free Bacon by Selected Cooking Treatments

A newly detected cooking-generated promutagenic fraction in nitrite-free bacon was evaluated to determine the heating conditions required for its formation. This apparent nonnitrosamine mutagenic activity was detected by the Ames mutagenicity assay when the product was heated by frying, baking, broiling, or high temperature autoclaving, but was not detected in microwave irradiated, steamed, or conventionally autoclaved samples. The ingestion of .the genotoxin(s) can be avoided by employing low temperature cooking methods or strictly controlling heating time. The toxicologic significance of exposures to this genotoxic fraction is unknown.     

Influence of ascorbic acid and pH on the formation of N-nitrosodimethylamine in cured pork containing added dimethylamine.

Under laboratory conditions simulating normal bacon curing, the conversion to N-nitrosodimethylamine (NDMA) of dimethylamine (DMA) added to pork, was 0.1%. Addition of sodium ascorbate to the brine was shown to suppress NDMA formation from added DMA in this simulated curing system and in experimental curing of pork middles spiked with DMA. Heating, by canning or frying, resulted in the formation of small amounts of NDMA in the lean and considerably higher concentrations in the fried fat. However, the lowest amounts of NDMA were found in the bacon cured in the presence of ascorbate.     

Measurement of Nitrosamine and Nitramine Formation from NO(x) Reactions with Amines during Amine-Based Carbon Dioxide Capture for Postcombustion Carbon Sequestration

With years of full-scale experience for precombustion CO(2) capture, amine-based technologies are emerging as the prime contender for postcombustion CO(2) capture. However, concerns for postcombustion applications have focused on the possible contamination of air or drinking water supplies downwind by potentially carcinogenic N-nitrosamines and N-nitramines released following their formation by NO(x) reactions with amines within the capture unit. Analytical methods for N-nitrosamines in drinking waters were adapted to measure specific N-nitrosamines and N-nitramines and total N-nitrosamines in solvent and washwater samples. The high levels of amines, aldehydes, and nitrite in these samples presented a risk for the artifactual formation of N-nitrosamines during sample storage or analysis. Application of a 30-fold molar excess of sulfamic acid to nitrite at pH 2 destroyed nitrite with no significant risk of artifactual nitrosation of amines. Analysis of aqueous morpholine solutions purged with different gas-phase NO and NO(2) concentrations indicated that N-nitrosamine formation generally exceeds N-nitramine formation. The total N-nitrosamine formation rate was at least an order of magnitude higher for the secondary amine piperazine (PZ) than for the primary amines 2-amino-2-methyl-1-propanol (AMP) and monoethanolamine (MEA) and the tertiary amine methyldiethanolamine (MDEA). Analysis of pilot washwater samples indicated a 59 μM total N-nitrosamine concentration for a system operated with a 25% AMP/15% PZ solvent, but only 0.73 μM for a 35% MEA solvent. Unfortunately, a greater fraction of the total N-nitrosamine signal was uncharacterized for the MEA-associated washwater. At a 0.73 μM total N-nitrosamine concentration, a ～25000-fold reduction in concentration is needed between washwater units and downwind drinking water supplies to meet proposed permit limits.     

2种复合香辛料精油对西式培根安全品质的影响

为验证前期研究的2 种对N-亚硝胺具有阻断作用的复合香辛料精油（compound spice essential oil,CSEO）在西式培根中的实际应用效果,在西式培根加工腌制环节设计3 组实验：1）空白对照组：注射20 mL/100 g基础腌制液（含亚硝酸钠、异抗坏血酸钠、复合磷酸盐等）;2）CSEO-ND组：在基础腌制液中添加由胡椒精油、姜精油、花椒精油、八角精油和丁香精油组成的对N-二甲基亚硝胺（N-nitrosodimethylamine,NDMA）具有较强抑制作用的CSEO-ND;3）CSEO-NP组：在基础腌制液中添加由花椒精油、八角精油、麻椒精油、丁香精油和迷迭香精油组成的对N-亚硝基吡咯烷（N-nitrosopyrrolidine,NPYR）有较强抑制作用的CSEO-NP。对西式培根产品烧烤（200 ℃,5 min）后的感官评分、烧烤前后pH值、亚硝酸盐、生物胺以及N-亚硝胺含量进行测定,并将西式培根产品置于（36±1） ℃条件下进行破坏性实验。结果表明：CSEO-ND可赋予西式培根特有的风味,提高产品的整体可接受性,降低产品中亚硝酸盐残留量（23.52 mg/kg）,提高抗氧化性,抑制生物胺总量的增加（抑制率为43.95%）,有效控制NDMA（抑制率为60.18%）和NPYR（抑制率为64.88%）的形成;CSEO-NP具有较强的抑菌性,能很好地控制产品中组胺、酪胺、腐胺等毒性较强的生物胺形成,对NDMA（65.99%）和NPYR的抑制率（66.13%）均高于CSEO-ND,但产品风味受到一定影响,亚硝酸盐残留量（40.00 mg/kg）超过国家限量标准（30 mg/kg）。     

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.     

Reduction of acrylamide formation by vanadium salt in potato French fries and chips

The effects of vanadyl sulphate on the formation of acrylamide have been studied in fried potato products, such as French fries and chips. Acrylamide formation was inhibited by 30.3%, 53.3% and 89.3% when the sliced potato strips were soaked in 0.001, 0.01 and 0.1 M vanadyl sulphate (VOSO₄) solutions, respectively, for 60 min before frying. Moreover, 57.7%, 71.4% and 92.5% inhibition of acrylamide formation was observed when chips were soaked in the respective vanadyl sulphate solution before frying. In a separate model reaction, a solution containing an equimolar concentration of l-asparagine and d-glucose showed a significant inhibition of acrylamide formation when heated at 150 °C for 30 min in the presence of vanadyl sulphate (VOSO₄). The results indicate that the binding of VO²⁺ to asparagine and the decrease in the pH of the potato samples resulted in a significant reduction of acrylamide formation in fried potato products.     

A survey of fish products for volatile N-nitrosamines

A study was undertaken to determine the levels of nitrate, nitrite and volatile N-nitrosamines of various fish products (halibut, salmon, cod, sole, ocean perch, scallops). The samples were analysed for five volatile nitrosamines, namely dimethyl-nitrosamine (DMN), diethylnitrosamine (DEN), dibutylnitrosamine (DBN), nitrosopyrrolidine (NPyr) and nitrosopiperidine (NPip), all of which are potent carcinogens. Both gas–liquid chromatographic (Coulson electrolytic conductivity detector, pyrolytic mode) and thin-layer chromatographic methods were used for estimating the levels of nitrosamines. The average level of nitrate was 8 part/10⁶ (range 0–94 parts/10⁶), and nitrite was present in traces only. Traces of DMN (3–12 parts/10⁹) were found in some uncooked (raw) fish. Increased levels of DMN (3–18 parts/10⁹) and traces of DEN (4–14 parts/10⁹) were observed after baking and frying, indicating formation of these compounds during cooking. None of the samples contained DBN, NPyr or NPip. In 10 out of 15 samples the identities and levels of DMN and DEN were confirmed by gas liquid chromatography–high resolution mass spectrometry.     

低温真空油炸山药脆片的工艺研究

对比不同油炸方式制作山药片,探究低温真空油炸山药脆片的优点及最佳生产工艺.以感官评价、含油率为考核指标,采用单因素和响应面方法对工艺进行优化,并通过色差仪和扫描电镜做色度及微观结构的观察.试验表明真空低温油炸山药脆片在色泽及含油率明显低于普通油炸方法,其最佳加工工艺为切片厚度6 mm,汽蒸5 min,油炸温度为95℃,...