Effect of the addition of nitrate to milk on the formation of volatile N-nitrosamines and apparent total N-nitroso compounds

 Saint-Paulin, a French semihard cheese, was manufactured from milk with and without added NO₃ ^–. Reference and experimental cheeses were analysed at different stages of ripening for the presence of apparent total N-nitroso compounds (ATNC) by chemical denitrosation and chemiluminescence detection (thermal energy analyser). The fate of NO₃ ^– and NO₂ ^–was also scrutinized. The levels of ATNC and of volatile N-nitrosamines were followed during ripening. After 60 days of ripening, ATNC were detected at concentrations of 27 μg NO-N/kg and 64 μg NO-N/kg in the cheeses obtained from milk with and without added NO₃ ^–, respectively. The NO₃ ^– contents of both cheeses were nearly the same, and below 5 mg/kg. The occurrence of NO₂ ^–was not observed. No relationship was found between the NO₃ ^– contents and the contamination of the cheeses by volatile N-nitrosamines. At the beginning of ripening, the cheeses manufactured with added NO₃ ^- showed high levels of ATNC (mean value 5800 μg N-NO/kg with large variations of 570–15210 μg NO-N/kg). These ATNC contents rapidly decreased during the first days of ripening (96%), but decreased much more slowly during the following days. An hypothetical mechanism, attempting to explain the disappearance of ATNC, involving the formation of alkylated species in the cheese was proposed. Received: 30 March 1998 / Revised version: 7 October 1998     

NITRATE REDUCTION AND ATNC FORMATION BY BREWERY WILD YEASTS

Control of NAD(P)H-dependent nitrate reductase (NR) and nitrite reductase (NiR) synthesis and activity in Hansenula anomala, Rhodotorula glutinis, Candida versatilis and Brettanomyces anomalus was investigated. Activities of both enzymes were high in all four yeasts when cultured in a medium containing nitrate as the sole source of cell nitrogen, but ammonia and amino-nitrogen were shown to rapidly repress nitrate assimilation and reduction. Little or no NR or NiR activity was detected in wort or beer-grown cultures. Only B. anomalus was found to excrete nitrite when grown in wort, but not at a concentration which could be chemically reduced to allow formation of a detectable concentration of N-nitrosamines. Cask beer (containing 16 mgl^?1 nitrate) contaminated with nitrate reducing wild yeasts, pre-grown on nitrate, contained < 10 μgl^?1 Apparent Total N-Nitrosocompounds (ATNC) following 10 weeks storage. It was concluded that contamination of wort, fermentation and finished beer by nitrate-reducing wild yeast is unlikely to result in formation of detectable ATNC .     

低共熔溶剂-超高效液相色谱-大气压化学离子化-串联质谱法测定火腿肠中9种N-亚硝胺

目的 建立低共熔溶剂(deep eutectic solvents, DES)-超高效液相色谱-大气压化学离子化-串联质谱法快速测定火腿肠中9种N-亚硝胺污染物的分析方法。方法 样品经水稀释,微量DES分散萃取,50%甲醇水复溶,Agilent Infinitylab Poroshell 120 EC-C18 (2.1 mm×150 mm, 2.7 μm)色谱柱分离,大气压化学电离源电离,多反应监测模式检测,内标法定量分析。结果 9种N-亚硝胺在5~60 ng/mL范围内线性关系良好,线性相关(r)均>0.999。方法检出限为0.1~0.3 μg/kg, 定量限为0.5~1.0 μg/kg, 回收率为72.1%~111.6%, 相对标准偏差为0.9%~8.4%。结论 低共熔溶剂对N-亚硝胺的萃取效果佳,可以解决传统操作步骤烦琐的问题。本方法有机试剂用量少,绿色环保,适用于火腿肠中9 种N-亚硝胺的快速、精准检测。     

干酪乳杆菌SB27降低N-亚硝胺对IEC-6细胞毒性作用研究

该研究选用具有益生功能的干酪乳杆菌（Lactobacillus casei）SB27为研究对象,采用菌落计数法分析N-亚硝胺（N-二甲基亚硝胺（NDMA）、N-二乙基亚硝胺（NDEA）、N-亚硝基吡咯烷（NPYR）和N-亚硝基哌啶（NPIP）（0～80 μg/mL）在MRS液体培养基中对干酪乳杆菌SB27生长的影响,并以维生素C（VC）（50 μmol/L）为阳性对照,采用细胞计数试剂盒（CCK）-8法分析干酪乳杆菌SB27（103～106 CFU/mL）降低N-亚硝胺对大鼠肠道黏膜细胞IEC-6毒性的损伤。结果表明,N-亚硝胺在MRS液体培养基中对干酪乳杆菌SB27的生长增殖无显著影响（P＞0.05）。干酪乳杆菌SB27可降低NDMA、NDEA、NPYR及NPIP对大鼠肠道黏膜细胞IEC-6的毒性损伤。     

吹扫捕集和气相色谱(PT-GC)联用测定水中N-亚硝基胺

该文建立涉水橡胶材料在浸泡试验过程中析出的三种N-亚硝胺类物质(N-亚硝基二乙胺、N-亚硝基二丙胺和N-亚硝基二丁胺)的吹扫捕集-气相色谱联用检测方法。三种化合物标准曲线的相关系数在0.990～0.995之间,日内相对标准偏差(RSD)小于8%,空白加标回收率在90.0%～102.1%之间,3种物质的检出限分别是5.3,2.7,1.5μg/L。     

3 种氨基酸对西式熏煮火腿品质及N-亚硝胺形成的影响

为探讨氨基酸对西式熏煮火腿品质及N-亚硝胺（N-亚硝基二甲胺（N-nitrosodimethylamine,NDMA）、N-亚硝基二正丙胺（N-nitrosodi-npropylamine,NDPA）和N-亚硝基吡咯烷（N-nitrosopyrrolidine,NPYR））形成的影响,将不同含量亚硝酸钠（0、150、480 mg/kg）和3 种氨基酸（精氨酸、丙氨酸、脯氨酸）1 000 mg/kg添加于西式熏煮火腿配料中,研究其对西式熏煮火腿产品的质构、色差、pH值、硫代巴比妥酸反应产物（thiobarbituric acid reactive substances,TBARS）值、水分和蒸煮损失等品质变化,和对亚硝酸盐残留量及N-亚硝胺形成作用的影响规律。结果表明,精氨酸和丙氨酸降低了亚硝酸盐残留量,添加脯氨酸组则相反;3 种氨基酸均显著增加NDPA含量,加脯氨酸产品的NPYR含量显著高于其他2 种氨基酸的产品;3 种氨基酸均显著增加火腿的硬度、内聚性、咀嚼性、a*值和pH值,并降低产品的L*、b*值、TBARS值和蒸煮损失;精氨酸增强弹性,丙氨酸和脯氨酸降低弹性;精氨酸和脯氨酸增强胶着性,丙氨酸降低胶着性。3 种氨基酸均可改善产品品质,抑制产品氧化,可作为品质改良剂,但会促进N-亚硝胺的形成,应减少产品中这3 种氨基酸的含量抑制N-亚硝胺的生成。本研究可为肉类产品品质的提高、N-亚硝胺抑制和形成机理的深入研究奠定理论基础并提供借鉴参考。     

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。