Evaluation of Nitrite in Ready-Made Soups

As time is very important for today’s people, ready-made soups in different forms (powder, liquid, canned) are consumed highly. Nitrite has been implicated with a variety of long-term adverse effects and has been of interest to public health providers and governmental regulators for the last 40 years. The present study was aimed to assess nitrite levels in commercially available soups in powder form by using a spectrophotometric method and to evaluate the possible toxicological outcomes. For this purpose, 66 ready-made soups were randomly collected and divided into seven groups: tomato-, chicken-, yoghurt-, mushroom-, lentil-, meat-, and vegetable-based. The minimum–maximum and median levels of nitrite content of the soup groups are 28–2,091 (median, 108), 53–400 (median, 136), 26–129 (median, 47), 58–197 (median, 109), 12–225 (median, 38), 12–555 (median, 40), 184–1229 (median, 389) mg kg⁻¹, respectively. Meat- and tomato-based soups have the highest nitrite contamination among the groups. On the other hand, acceptable daily intake (ADI) of nitrite given by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and Scientific Committee on Food (SCF) is 0–0.07 mg kg⁻¹ (body weight, b.w.) per day, while Environmental Protection Agency (EPA) has set a reference dose (R_fD) of 0.10 mg nitrite nitrogen per kilogram b.w. per day (equivalent to 0.33 mg nitrite ion per kilogram b.w. per day). This means that the highest intake of nitrite a 70-kg person must be no more than 4.9 mg in 1 day according to JECFA and SCF and 7 mg kg⁻¹ b.w. per day according to EPA. However, nitrite intake from one portion (13 g) meat-based soups, when calculated with median daily intake levels (5.05 mg), exceeds the limit of JECFA and SCF. With long-term daily consumption of high nitrite levels exceeding ADI, the risk of mild to moderate methemoglobinemia would be increased, especially for susceptible populations such as young children and elderly. Besides, the higher intake of nitrite from foodstuff and other sources may induce the formation of carcinogenic nitrosamines which are formed endogenously from nitrites and nitrates. The first results of the study were presented as a poster at the 121st AOAC Annual Meeting & Exposition, held at Anaheim, California USA, September 16–20, 2007.     

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.     

离子色谱法测定牛奶或奶粉中亚硝酸盐 硝酸盐及氯化物

牛奶或奶粉中的亚硝酸盐、硝酸盐及氯化物经溶解稀释后可直接进样至离子色谱仪中进行测定；样品中加入亚硝酸盐、硝酸盐及氯化物标准后测定，两者的准确度及精密度均取得满意结果。6份样品采用本方法测定结果与国家标准[GB／T5413．32-1997及GB／T5413．32-1997（第二法）]采用的方法测定结果比较无显著性差异：     

抑制电导-离子色谱法同时测定肉制品中亚硝酸盐和硝酸盐

建立了一种灵敏、快速的同时测定肉制品中亚硝酸盐和硝酸盐的抑制电导-离子色谱分析方法。样品经超声提取后,以DIONEX IonPac AS19(4mm×250mm)色谱柱分离,用DIONEX EG40淋洗液发生器自动淋洗,采用梯度洗脱方式,以抑制电导检测器进行检测。实验表明,硝酸盐和亚硝酸盐的方法检出限(3S/N)为0.6mg/kg和0.8mg/kg,在0.1～50ug/ml范围内呈良好线性关系,回收率为98.4%和96.5%,重复性(RSD)为2.8%和3.2%。本方法灵敏度高,重复性好,可用于肉制品中的亚硝酸盐和硝酸盐的检测。     

Determination of nitrates,nitrites and oxalates in food products by capillary electrophoresis with pH-dependent electroosmotic flow reversal

This paper describes an innovative and rapid capillary electrophoretic method for the simultaneous analysis of nitrates, nitrites and oxalates, which are anions of food interest. The novelty of our method is based on reversing the electroosmotic flow without using any buffer additive nor performing a capillary coating, but simply employing a buffer at low pH values.     

植酸对白菜乳酸发酵过程中微生物生长代谢及亚硝酸盐积累影响初探

白菜乳酸发酵过程中添加不同浓度的植酸，研究其对发酵过程中细菌总数、pH值、亚硝酸盐含量变化的影响。结果表明，添加植酸对酸及上述三个指标影响明显。     

Effect of tomato paste and nitrite level on processing and quality characteristics of frankfurters

Fourteen treatments of frankfurters (18% fat) were produced with two levels of sodium nitrite, 0 and 150mg/kg (0.015%), and seven levels (0%,2%,6%,8%,12% and 16%) of tomato paste with 12% soluble solids The higher the tomato paste level the higher the preference of consumers for frankfurters based on their colour. Frankfurters with 16% tomato paste had a sour taste while those with 12% tomato paste were the most acceptable. In a 2nd experiment three treatments of frankfurters (18% fat) were produced with 0, 50 and 100mg/kg of sodium nitrite and 12% tomato paste and a fourth (control) with only 150mg/kg sodium nitrite. Treatments with 12% tomato paste had lower (p<0.05) pH values and residual nitrite, and higher (p<0.05) thiobarbituric acid values, lightness and yellowness than control. Frankfurters with reduced levels of sodium nitrite (50 and 100mg/kg) and 12% tomato paste had the highest (p<0.05) redness. Storage time affected (p<0.05) all quality attributes. The nitrites added to frankfurters can be reduced from 150mg/kg to 100mg/kg in combination with 12% tomato paste without any negative effect on the quality of the product.     

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.     

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。     

Interactive Effects of Fly Ash and CNI on Corrosion of Reinforced High-Performance Concrete

The interactive effects of fly ash and CNI in corrosion of reinforced concrete were investigated. A 3⁴ full factorial design was developed considering water to cement ratio, fly ash percent, CNI and cracked condition as factors. The response factors were the weight loss calculated from Linear Polarization Resistance measurements and the pit depth of the steel bars embedded in concrete. Small-scale concrete slabs containing steel reinforcement with a cover depth of 20 mm were cast for this purpose. The slabs were subjected to a simulated marine environment with two cycles of wetting and drying per day during one year; after the exposure, the slabs were broken, the bars were cleaned and the pith depth measured by using SEM. Under the studied conditions, it was found that CNI alone does not provide corrosion protection of the steel reinforcement even for uncracked silica fume concrete in a 0.45 w/c ratio; however, the combination of CNI and fly ash can be useful to overcome this problem. The results indicate that low w/c ratio concrete in its crack state creates conditions suitable for the development of pitting corrosion.