离子色谱法同时测定纯化水和饮用水中亚硝酸盐和硝酸盐

目的:建立离子色谱法同时测定纯化水和饮用水中亚硝酸盐和硝酸盐的含量的方法。方法:以物质的量浓度为3.2 mmol/L的Na₂CO₃和物质的量浓度为1.0 mmol/L的NaHCO₃为淋洗液,以物质的量浓度为50 mmol/L的硫酸为再生液,采用MIC型离子色谱仪,METROSEP A SUPP 5-250柱分离,电导检测器检测,外标法定量。结果:亚硝酸盐:线性范围0.05 mg/L～2.0 mg/L,相关系数0.999 5,样品加标回收率为97.33%～98.67%,RSD为0.6%～1.2%,检出限为0.001 mg/L,定量限为0.002 mg/L;硝酸盐:线性范围0.01 mg/L～1.0 mg/L,相关系数0.999 3,样品加标回收率为95.44～97.04%,RSD为0.5%～0.7%,检出限为0.001 mg/L,定量限为0.002 mg/L。结论:该方法灵敏、快捷,能够用来同时测定纯化水和饮用水中亚硝酸盐和硝酸盐的含量,适用范围广。     

应用便携式快速水质检测仪测定生活用水中的亚硝酸盐

采用盐酸萘乙二胺分光光度法利用便携式快速水质检测仪测定生活用水中的亚硝酸盐。结果表明线性关系为y=6.7684x-0.0002,R2为0.9999。在测定生活用水样品时,与采用TU-1901标准方法数据相比其相对误差在±0.36%之内。实验证明便携式快速水质检测仪测定生活用水中的亚硝酸盐与国标方法盐酸萘乙二胺分光光度法(GBT 7493-1987)相比,没有显著性差异,且仪器具有方便快速的特点。     

溶剂浮选吸光光度法测定痕量NO_2~-离子

本文拟定了用溶剂浮选吸光光度法测定水相中痕量 NO_2~-离子的方案.以正戊醇为有机溶剂,CPB(溴化十六烷基吡啶)为捕收剂,浮选 NO_2~-与对氨基苯磺酸及α-萘胺所形成的偶氨染料,在534mm 波长处以试剂空白为参比测定吸光度,其表现摩尔吸光系数为6.6×10~6Lmol~(-1)cm~(-1),检测下限为0.3ppb.用于实际样品中痕量 NO_2~-离子的测定,五次测定的相对标准偏差为1.6％.1000倍于 NO_2~-离子的 Fe(Ⅲ)、Al(Ⅲ)、Cu(Ⅲ),Pb(Ⅱ)、Zn(Ⅱ)、Mg(Ⅱ)、Ca(Ⅱ)、SO_4~(2-)、NO_3~-、Cl~-、Br~-、PO_4~(3-)等共存物不干扰测定.     

改性超支化聚（胺-酯）对亚硝酸根的吸附性能研究

以十八烷基三氯硅烷对超支化聚（胺-酯）进行改性,合成了改性的超支化聚（胺-酯）。改性的超支化聚（胺-酯）是一种既具有大量的端羟基且易从中水中分离出来的超支化聚（胺-酯）。将改性的超支化聚（胺-酯）用于吸附亚硝酸根离子,实验结果表明：改性的超支化聚合物对亚硝酸根离子的最大吸附量可达149．7mg／g,在酸性溶液中吸附量还将大大增加。     

高效自养型硝化细菌的分离及硝化条件优化

以焦化废水处理系统中的活性污泥为菌源,分离出具有较高硝化能力的自养型硝化细菌Z2。液体培养基中培养4天,菌株Z2的硝化效果可以达到100%。通过在不同温度、初始pH、摇床转速下研究其对菌株Z2硝化效果影响,得到该菌株的最优硝化条件为温度30℃,pH8.0,摇床转速250r/min。不同接种量的研究表明,增大接种量有利于硝化作用的进行。当底物亚硝酸盐氮浓度从101.51mg/L增加到507.55mg/L时,并未抑制该菌株硝化作用的进行。硝化过程中培养体系的pH逐渐增大,在理论上有利于硝化作用的进行。     

Effects of organic tomato pulp powder and nitrite level on the physicochemical,textural and sensory properties of pork luncheon roll

Nine treatments of pork luncheon roll produced with three sodium nitrite levels (0, 0.05 and 0.1%) and three tomato pulp powder (TPP) levels (0, 1.5 and 3%) were assessed at three storage times (2, 7 and 14 d). The effects of enrichment with TPP on composition (protein, fat, moisture and ash), pH, colour (CIE L*, a*, b*), nitrosomyoglobin (NOMb) content, lipid oxidation (TBARS), residual nitrite content, total viable count (TVC) texture profile analysis (TPA) and sensory analysis of cooked pork luncheon roll were investigated. Decreasing the level of nitrite increased (p < 0.001) the pH, the NOMb value (p < 0.001), lipid oxidation (p < 0.001) and the residual nitrite content (p < 0.001) and affected the colour of the cooked product. The reduction in nitrites had no effect on the composition and texture of the pork luncheon rolls. Adding TPP reduced (p < 0.001) the pH and increased (p < 0.001) the colour parameters a* and b* of both the raw luncheon roll formulation and the cooked luncheon roll product. TPP, particularly at 3% had a detrimental effect on the texture of pork luncheon rolls by decreasing hardness (p < 0.001), gumminess (p < 0.001) and chewiness (p < 0.001) and increasing cohesiveness (p < 0.001). The TBA value increased (p < 0.01) with the three main factors (nitrite, TPP, day) but was in all cases well below the 2 mg MDA/kg threshold. TVCs for all treatments and storage days were below the TVC limit for this type of cooked product. The pork luncheon roll formulated with 50 mg nitrite and 1.5% TPP had similar or enhanced sensory attributes compared to the luncheon roll containing no TPP and a nitrite level of 100 mg/kg of product.     

Ascorbic acid,nitrate, and nitrite concentration relationship to the 24 hour light/dark cycle for spinach grown in different conditions

Nitrate, nitrite and ascorbic acid (vitamin C) concentrations were determined for spinach (Spinacia oleracea L.) over a 24 h period to determine if light intensity (including dark periods) at time of harvest impacts concentrations in raw vegetables. Nitrate, nitrate and ascorbic acid concentrations varied significantly over the 24 h period and appeared to be related to changes in light intensity. Light intensity at the time an experimental sample is collected may affect the concentration of some constituents that a researcher is studying. Also, nitrate and nitrite concentrations in raw spinach can be reduced by harvesting at the best time of day. The highest nitrate concentrations in spinach occurred in the dark just prior to an increase in light intensity. Ascorbic acid was near its highest level for the 24 h period when the light intensity initially increased, then decreased to its lowest level around 3–6 h later.     

Kinetics of nitrite evaluated in a meat product

The evaluation of the efficiency with which the reactions involving nitrite proceed in mortadella and of the effect exercised on their kinetics by some variables (ingoing amount of sodium nitrite and temperature) is the purpose of this work. Kinetics parameters were calculated at each level of nitrite added (40, 70, 100 and 150 mg/kg) and at five temperature (55°, 60°, 65°, 70° and 72 °C). While the colour formation reaction is favoured by low activation energy, it becomes crucial to enable nitrite to proceed according to direct reduction thus preventing an increase in nitrate concentration as well as an excess of nitric oxide in the product. Kinetics data suggest that this scope is performed when the product achieves the temperature of 65 °C as fast as possible with an ingoing amount of sodium nitrite of 70 mg/kg.     

Beyond celery and starter culture: advances in natural/organic curing processes in the United States

Over the past 10years there has been ongoing development of curing processes with natural ingredients designed to meet consumer demand and regulatory requirements for natural and organic processed meats. Initially, these processes utilized celery concentrates with a high nitrate content combined with a nitrate-reducing starter culture. Subsequent advances included celery concentrates with the nitrate converted to nitrite by suppliers. Further, as questions developed concerning reduced concentration of preservatives and the microbiological safety of these processed meats, additional advances have resulted in a wide variety of ingredients and processes designed to provide supplementary antimicrobial effects for improved product safety.     

Effect of rosemary extract dose on lipid oxidation, colour stability and antioxidant concentrations, in reduced nitrite liver pâtés

The oxidative stability of liver pâté was investigated in relation to different doses of rosemary extract (RE) and sodium nitrite. Colour stability, lipid oxidation (TBARS) and concentrations of ascorbic acid, α-tocopherol, carnosic acid and nitrite were measured on the batters before cooking and on the cooked liver pâté before and after exposure to light and air for 48 h at 4 °C. Results showed that the use of RE significantly reduced lipid oxidation, whereas it had no effect on colour stability. Ascorbic acid and nitrite concentrations were significantly higher and lower respectively when RE was added. RE dose-dependently increased the concentration of carnosic acid. Lower sodium nitrite doses resulted in significantly lower nitrite concentrations and slightly lower TBARS values. It was concluded that in liver pâté sodium nitrite levels may be lowered to 80 mg/kg without negatively affecting colour and lipid stability and that the use of RE may help in maintaining lipid stability.