Trace elements in Canadian field peas: a grain safety assurance perspective

Canada is a significant exporter of field peas and, thus, issues of food safety are important in all grain and food products within the international marketplace. Environmental contaminants, such as trace elements, may be present in all foods and, as a result, international standards have been established for a number of toxic trace elements, such as cadmium, lead, mercury and arsenic, in raw food commodities and food products. The Canadian Grain Commission has undertaken a baseline study of various trace elements in Canadian peas to ensure compliance with international food safety legislation. Mean total cadmium content was found to be 0.023 mg kg^?1; arsenic and lead mean values were below the method limit of quantification of 0.050 mg kg^?1 and the total mean mercury level was below the quantification level of 0.002 mg kg^?1. All measured values in the study were below the maximum residue levels (MRLs) established by the FAO and WHO in the Codex Alimentarius. The mean total selenium content was 0.331 mg kg^?1, with 56% of the measured values exceeding the MRL established by the People's Republic of China (PRC) of 0.3 mg kg^?1. No Codex MRL has been established for selenium as it is regarded as an essential trace element for human health and the PRC is currently reviewing its MRL for selenium in light of this fact. For those parts of the world where selenium-deficiency is of nutritional concern, the higher level of selenium in Canadian peas and their products may be of nutritional benefit.     

我国贝类产品中重金属镉的危害及污染分析

以抽样调查的贝类产品中镉含量数据为依据,从危害识别、危害描述、暴露评估、风险描述等方面对贝类产品中重金属镉的危害及污染水平进行分析。结果显示,虽然按照现行国家标准,所调查贝类中镉含量是超标的,但是食用人群镉的理论最大周摄入量(TMWI)低于食品添加剂专家委员会(JECFA)提出的镉的暂定每人每周允许摄入量(PTWI),因此,被调查区域贝类的食用对人健康造成危害的可能性很小。本文在危害分析的基础上,对现行国家标准贝类中镉限量进行了探讨,为标准修订和指导消费提供依据。     

Removal of Cadmium and Lead from Aqueous Solution by Enterococcus faecium Strains

ABSTRACT:  Foods may be contaminated with heavy metals, which, even in small quantities, possess detrimental effects on human health. The aim of the present study was to investigate the uptake of cadmium or lead from an aqueous medium frequently found in foods, by 2  Enterococcus faecium  strains ( E. faecium  EF031 and  E. faecium  M74). Also, the effects of the bacterial viability, incubation (contact) time, and pH on the binding capacities and binding stability were assessed. The results showed that both of the strains efficiently removed cadmium and lead. While EF031 removed 77.3% to 98.1% of cadmium and 66.9% to 98.9% of lead, M74 removed 53.5% to 91% of cadmium and 42.9% to 93.1% of lead throughout a 48 h incubation period at pH 5. It was found that, at 1 h, EF031 and M74 strains removed cadmium and lead, which was more than 60% of total removed cadmium and lead throughout the whole incubation period of 48 h. It suggests that the uptake of cadmium and lead by EF031 and M74 strains is a rapid process. The binding of both heavy metals increased with increasing pH of an aqueous medium and was the highest at pH 5. Also, the complexes formed between both heavy metals and bacterial cells were found to be stable. These findings indicate that  E. faecium  strains used in the study are able to bind the 2 heavy metals and may be used in the production of fermented functional foods, which will be healthy via its detoxification properties.     

新型螺旋式走向电镀机组

为提高电镀的自动化程度,减少生产线占地面积,增加电镀机组可镀产品的种类,节能降耗,研制出一种螺旋式走丝电镀机。该机电镀性能好,镀层结晶致密,可镀品种多,镀液消耗少,自动化程度高,环境污染少。     

浅谈金属丝的快速光亮电镀

从实践的角度探讨金属丝快速光亮电镀问题，介绍有关的工艺配方和克服生产线长度不足的方法。     

Determination of total nitrogen and cyanide nitrogen in cassava

Heating of intact cassava leaves causes liberation of hydrogen cyanide. This phenomenon appears to be caused by β-glucosidase-catalysed decomposition of the cyanogenic glycosides linamarin and lotaustralin. Because of these losses, many previously determined values for total nitrogen in cassava (and other cyanogenic plants) are probably in error as plant materials used for Kjeldahl determinations are often dried at 70–90°C. Liberation of cyanide from intact cassava leaves by heating at 80°C is more complete than liberation by the homogenisation methods commonly used. Homogenisation of cassava leaf tissues with liquid nitrogen or dry ice gives somewhat lower values, and these materials are often not readily available in areas where cassava is studied. The basis of a relatively simple procedure for the isolation of hydrogen cyanide from cassava leaves is suggested.     

鲁氏酵母脱除水溶液中Cd~(2+)的研究

研究了鲁氏酵母(Zygosaccharomyces rouxii)CICC1379作为吸附剂对水溶液中镉的脱除作用。结果表明:温度和振荡频率对Cd2+脱除率影响不大,初始pH和菌体浓度则影响很大。初始pH3-5,脱除率均随pH增大而增大。pH5-7是鲁氏酵母对低、高2组溶液的脱除Cd2+的最适pH。Cd2+脱除率随时间变化的曲线表明,酵母在10.22mg/L和53.39mg/LCd2+溶液中,在5min内完成大部分吸附并在30min内达到吸附平衡。     

阳极溶出伏安法测定氯化锌-氯化铵电解制锌体系中铅和镉

采用阳极溶出伏安法,建立了在ZnCl₂-NH₄Cl体系中,使用乙二胺四乙酸二钠(EDTA)和磺基水杨酸消除Cu²⁺对Pb²⁺测定的影响,不经预分离同时测定溶液中Pb²⁺和Cd²⁺的方法。在扫描电位为-0.80～-0.30 V、富集电位为-0.85 V、富集时间为100 s、扫描速率为0.015 V/s的优化试验条件下,Pb²⁺和Cd²⁺分别在-0.48 V和-0.68 V处有灵敏的溶出峰。溶液中可能存在的常见离子不干扰测定。Pb²⁺、Cd²⁺浓度分别在9.7×10^-9～2.4×10^-4、1.8×10^-8～8.9×10^-5 mol/L范围内与其峰电流呈良好的线性关系,相关系数分别为0.995和0.998。方法中Pb²⁺、Cd²⁺的检出限分别为3.9×10^-9、1.9×10^-9 mol/L。采用实验方法测定了ZnSO₄电解液和ZnCl₂-NH₄Cl电解液中的Pb²⁺和Cd²⁺,结果的相对标准偏差(RSD,n=6)分别为0.83%～2.1%、0.56%～0.75%,回收率分别为89%～108%、92%～104%。