稻谷不同部位多元素分布规律

以收集自三省的66份稻谷为研究对象,通过加工研磨获得糙米和精米,通过ICP-MS获得并筛选出包含铅、镉和砷在内的17种无机元素,结合出糙率和整精米率数据,并研究其在稻谷不同部位(颖壳、米糠层和精米)中的分布规律,探讨形成原因。结果表明,58.3%～73.2%的铅分布在颖壳层,米糠层和精米中铅含量总量相近,分别在15.9%～22.8%和9.8%～18.9%范围内;镉元素44.3%～54.5%分布在精米,而在米糠层含量范围是22.8%～44.1%。对于砷元素,在精米中的残留率为18.6%～22.8%。对于其他的无机元素,大部分在精米加工过程留存率不高于30%。     

X射线荧光光谱法测定稻谷中镉、铅和无机砷

选用3种型号X射线荧光光谱仪,测定稻谷样品中的镉、铅和总砷含量,并分别与GB/T5009.15—2003镉、GB/T 5009.12—2003铅和GB/T 5009.11—2003无机砷标准方法测定结果进行比较。67个稻谷样品镉测定结果比较表明,两者的相关系数分别为0.971 1、0.850 9和0.972 9,均呈极显著相关,回归方程分别为Y=0.849 5X+0.062 1、Y=0.619 7X+0.049 3和Y=0.872X+0.006 4;定性判定正确率为65.7%~91.0%,检测结果在0.16 mg/kg≤0≤0.24 mg/kg范围内,定性判定正确率在38.1%~81.0%,检测结果在0.16 mg/kg或0.24 mg/kg范围内,定性判定正确率在78.3%~95.7%;定量判定符合率在19.4%~44.8%,检测结果在≤0.2 mg/kg范围内,定量判定符合率在17.6%~37.3%,检测结果在0.2 mg/kg范围内,定量判定符合率在25.0%~68.8%。通过对33个稻谷样品测定铅的结果和对60个稻谷样品测定总砷与无机砷的结果比较,测定结果之间不存在相关性。     

不完全消解——ICP-MS法同测稻谷中的铅砷镉

本文首先采用不完全消解法对稻谷样品进行前处理,研究了消解温度和时间对前处理效果的影响,进而以ICP-MS法对稻谷中的铅、砷、镉三种重金属元素含量进行测定,并对其准确度和精密性进行了测试。结果表明,不完全消解—ICP-MS法同测稻谷中的铅、砷、镉,回收率分别可达到铅(99.1%~106.7%)、砷(94.8~105.6%)、镉(90.2%~99.0%),与传统的微波消解法和压力罐消解法相比较,测定结果无显著性差异。该方法具有操作简便、污染少等优点,可满足大批量稻谷的铅镉砷的同时测量。     

稻谷加工过程中重金属的变化规律及品种差异

在湖南省选择5种不同品种的稻谷样品,经过砻谷和碾白将稻谷加工成不同加工精度的大米,分别测定其了总砷、汞、铅、镉的含量,旨在探讨加工精度与重金属含量的变化规律及品种间的差异性。结果表明,四种重金属在稻谷中分布极不均匀,除稻壳外,重金属含量由外到内逐渐降低;随着加工精度的提高,稻谷中的总砷、汞、铅、镉含量均呈下降趋势。因此,通过加工精度的提高,可在一定程度上降低加工产品中总砷、汞、铅、镉的含量,当稻谷的碾米率达到20%时,其总砷、汞、铅、镉含量的下降率可达53.7%、29.2%、57.5%和33.3%。此外,四种重金属在稻谷中的分布呈现一定的品种差异,     

稻谷加工产物的镉含量及累积量分析

分析镉在稻谷加工产物中的分布及含量,为稻谷加工利用及质量控制提供技术依据。以不同镉含量的稻谷为原料,采用石墨炉原子吸收光谱法测定砻谷、碾米及大米淀粉和蛋白制备过程中各产物中的镉含量,计算镉累积量。试验结果显示,稻谷砻谷、碾米过程中产物镉含量的顺序为糠层颖壳外层胚乳中间层胚乳核心层胚乳;核心层胚乳,即精米中的镉累积量最高,占稻谷镉总量的40%左右;淀粉和蛋白制备过程中间产物镉含量的顺序为蛋白产品黄粉淀粉产品,蛋白产品的镉累积量最高,占大米镉总量的53.21%,淀粉产品镉累积量仅占18.34%。可见,稻谷中镉的分布具有不均匀性。糙米籽粒由外到内镉含量逐渐降低,适当提高碾米精度可降低大米产品中的镉含量。精米中的镉主要富集在蛋白质中,而在淀粉中积累较少。大米淀粉的制备方法有望成为含镉大米加工利用的有效途径之一。     

稻谷水热加工过程中镉迁移规律研究

目的研究稻谷在蒸谷米水热加工过程中镉的迁移规律。方法以蒸谷米小试装置及生产线采集样品为研究对象,在优化碾米时间的基础上,在排除水分含量差异对测定结果的前提下,利用统计分析考察水热工艺(浸泡和蒸煮)对稻谷各部分(稻壳、米糠和精米)镉含量的影响。结果由实验数据推断,在水热过程中,镉的迁移主要发生在稻谷的内部,且主要是在浸泡时从精米向米糠迁移富集,而蒸煮工艺则对镉的分布变化影响很小;经过浸泡,精米中的镉含量可降低约40%;推测热水的浸泡一方面使胚乳淀粉分子间游离的镉部分溶出,一方面促使镉向络合能力更强的米糠蛋白迁移,最终导致其分布发生明显变化。结论该研究为在稻谷加工过程中实现重金属镉的消减提供了科学依据。     

电感耦合等离子体质谱法和液相色谱-原子荧光联用法分析广西籼稻谷中砷含量的分布

选取广西区内100份籼稻谷作为实验材料,将籼稻谷脱壳分别制成糙米和精度一级的大米,用电感耦合等离子体质谱仪(Inductively coupled plasma mass spectrometer,ICP-MS)和液相色谱-原子荧光联用仪(Liquid chromatography-atomic fluorescence spectrometer,LC-AFS)检测技术分别检测总砷和无机砷含量。结果表明该方法的标准曲线线性良好,总砷的检出限为0.0030ng/mL,无机砷的检出限为0.0139ng/mL;总砷和无机砷在糙米和精米中的分布不同,糙米总砷含量约是精米总砷含量的1.5倍,糙米无机砷含量约是精米无机砷含量的1.8倍,可见砷元素在稻谷中的分布主要富集在皮层中;而糙米中总砷含量约是糙米无机砷含量的1.6倍,可知糙米总砷含量高,其无机砷含量不一定高。     

米糠中砷、镉、铅分布规律的初探

为研究米糠中砷(As)、镉(Cd)、铅(Pb)含量分布,选取湖北产10种稻谷,测定了不同加工等级下得到的米糠中蛋白质、As、Cd、Pb的含量。结果表明,蛋白质含量不呈线性递减分布,从高到低为:二道米糠、一道米糠、三道米糠、四道米糠、精米;而As、Cd、Pb含量分布从高到低为:一道米糠、二道米糠、三道米糠、四道米糠、精米。     

铜藻中有害元素的脱除工艺优化及脱除前后砷形态的变化

为降低铜藻中有害元素铬、砷、镉、铅含量,对最佳脱除剂进行选择,通过单因素实验、正交试验优化脱除工艺,以及采用高效液相色谱-电感耦合等离子体质谱(HPLC-ICP-MS)联用技术分析脱除前后铜藻中砷形态的变化,并将优化后的工艺应用于羊栖菜、马尾藻。结果表明,以1.5% EDTA-2Na作为脱除剂,在料液比为1:30 g/mL,时间为4 h,温度为30 ℃的工艺条件下,对铬的脱除率为71.34%;对总砷的脱除率为66.32%,其中对毒性较大的As3+、As5+脱除率分别为100%、91.43%;对镉的脱除率为87.40%;对铅的脱除率为87.64%,脱除后铅的含量低于GB 2762-2017《食品中污染物限量》的限量规定,脱除后铜藻中岩藻黄质损失率在可接受范围内。该工艺对羊栖菜中的有害元素铬、砷、镉、铅的脱除率分别为57.27%、66.00%、87.14%、88.88%;对马尾藻中有害元素铬、砷、镉、铅的脱除率分别为55.56%、56.89%、87.14%、96.44%。此工艺简单易操作,能脱除大部分毒性较大的无机砷,且具有一定的适用性,为工业上降低海藻中有害元素的含量提供思路。     

2019年南宁市种植稻米重金属污染监测结果

试验目的:了解南宁市种植的稻米重金属污染情况,为当地政府做出食品安全决策提供依据。试验方法:采集南宁市15个大米种植县区共126个乡镇的605份大米和稻谷,其中外地产的大米67份,本地种植的稻谷和大米538份。按照GB 2762-2017《食品中污染物限量》标准方法检测铅、镉、无机砷和总汞含量。试验结果:稻谷和大米总检出率为78.28%,其中稻谷超标率为33.33%,高于大米20.95%(P<0.01);本地种植大米重金属超标率高于外地(P<0.05),其中本地种植大米中,镉的超标率为17.88%,无机砷为0.56%,铅为2.23%,总汞为0.84%;县级行政区域种植的大米铅、镉、无机砷的超标率高于城区(P<0.05);镉元素的最高检出值为1.23 mg/kg,是国家卫生标准规定的6.15倍;南宁市种植大米镉的EDI(每日摄入量)为0.000 5 mg/kg·d,THQ(目标危险系数)为0.43,THQ<1。结论:南宁市种植的稻米重金属检出率较高,其中大米中镉超标较严重。应联合农业、环保等部门采取切实有效的措施提升当地种植大米的质量,确保食品安全。     

电感耦合等离子体质谱法测定米豆腐中5种元素的含量

目的建立电感耦合等离子体质谱法同时测定米豆腐中铅、砷、汞、镉、铬5种有害元素含量的分析方法。方法样品经微波消解,超纯水定容,以锗、铟、铋为内标物质,用电感耦合等离子体质谱法同时测定铅、砷、汞、镉、铬。结果铅、砷、汞、镉、铬回收率分别为83.2%~92.5%、85.3%~93.2%、83.5%~95.2%、85.7%~94.0%、81.7%~96.0%,相对标准偏差(n=6)分别为3.7%、2.3%、3.1%、2.9%、3.9%。5种元素线性关系良好,相关系数(n=6)在0.9997~1.000。结论优化了样品前处理方法和仪器参数,可用于米豆腐中铅、砷、汞、镉、铬的测定。     

Total and inorganic arsenic in rice and rice bran purchased in Thailand

Concentrations of total and inorganic arsenic were determined in 180 samples of polished and brown rice of three rice types, namely white, jasmine, and sticky, and 44 samples of rice bran from these three rice types purchased in Thailand. Concentrations (expressed in nanograms per gram) of inorganic arsenic in polished white, jasmine, and sticky rice were 68.3 ± 17.6 (with a range of 45.0 to 106), 68.4 ± 15.6 (41.7 to 101), and 75.9 ± 24.8 (43.5 to 156), respectively, while those in the three brown rice samples were 124 ± 34.4 (74.5 to 193), 120 ± 31.6 (73.1 to 174), and 131 ± 35.6 (78.0 to 188), respectively. Inorganic arsenic concentrations (expressed in nanograms per gram) in rice bran produced from the three rice types were 633 ± 182 (375 to 919), 599 ± 112 (447 to 824), and 673 ± 195 (436 to 1,071), respectively. Rice bran contained concentrations of total and inorganic arsenic approximately seven and nine times higher, respectively, than those found in the corresponding polished rice. The levels of inorganic arsenic in the three rice types of both polished and brown rice were within the only published regulatory limit of 200 ng/g.     

Inorganic arsenic in rice bran and its products are an order of magnitude higher than in bulk grain

Rice is more elevated in arsenic than all other grain crops tested to date, with whole grain (brown) rice having higher arsenic levels than polished (white). It is reported here that rice bran, both commercially purchased and specifically milled for this study, have levels of inorganic arsenic, a nonthreshold, class 1 carcinogen, reaching concentrations of approximately 1 mg/kg dry weight, around 10-20 fold higher than concentrations found in bulk grain. Although pure rice bran is used as a health food supplement, perhaps of more concern is rice bran solubles, which are marketed as a superfood and as a supplement to malnourished children in international aid programs. Five rice bran solubles products were tested, sourced from the United States and Japan, and were found to have 0.61-1.9 mg/kg inorganic arsenic. Manufactures recommend approximately 20 g servings of the rice bran solubles per day, which equates to a 0.012-0.038 mg intake of inorganic arsenic. There are no maximum concentration levels (MCLs) set for arsenic or its species in food stuffs. EU and U.S. water regulations, set at 0.01 mg/L total or inorganic arsenic, respectively, are based on the assumption that 1 L of water per day is consumed, i.e., 0.01 mg of arsenic/ day. At the manufacturers recommended rice bran solubles consumption rate, inorganic arsenic intake exceeds 0.01 mg/ day, remembering that rice bran solubles are targeted at malnourished children and that actual risk is based on mg kg(-1) day(-1) intake.     

Cooking rice in excess water reduces both arsenic and enriched vitamins in the cooked grain

This paper reports the effects of rinsing rice and cooking it in variable amounts of water on total arsenic, inorganic arsenic, iron, cadmium, manganese, folate, thiamin and niacin in the cooked grain. We prepared multiple rice varietals both rinsed and unrinsed and with varying amounts of cooking water. Rinsing rice before cooking has a minimal effect on the arsenic (As) content of the cooked grain, but washes enriched iron, folate, thiamin and niacin from polished and parboiled rice. Cooking rice in excess water efficiently reduces the amount of As in the cooked grain. Excess water cooking reduces average inorganic As by 40% from long grain polished, 60% from parboiled and 50% from brown rice. Iron, folate, niacin and thiamin are reduced by 50–70% for enriched polished and parboiled rice, but significantly less so for brown rice, which is not enriched.     

主要重金属在污染稻谷籽粒中的分布规律研究

以湖南省稻谷为研究对象,检测分析稻谷籽粒的稻壳、糠粉、糙米、精米等加工产品中无机As、Cd、Pb、Hg 4种重金属的变化分布规律,并研究了当前稻谷加工工艺对主要重金属的脱除效果。结果表明:无机As、Cd、Pd、Hg 4种重金属均表现出糠粉中的含量显著高于其他部位的含量。碾米加工工艺可同时消减稻谷中4种重金属的含量,其中无机As消减效果最好,消减幅度可达39%。无机As、Cd、Pb、Hg在精米与糙米中的含量均成正比,其比值分别为0.61、0.93、0.83、0.93。通过该比值关系,可通过碾米工艺获得重金属含量达标的稻谷无机As、Cd、Pb、Hg的限量值分别为0.328、0.215、0.241、0.021 5 mg/kg。     

粳稻谷中镉和无机砷分布探讨

通过对糙米和大米中镉和无机砷含量的分析,发现镉在粳稻谷中分布较均匀,其含量在糙米和大米中基本一致;而无机砷在粳稻谷中主要分布在表皮,糙米通过精加工碾磨成大米后,其无机砷含量约降低了2倍。为去除粮食中重金属残留,实现粮食资源的合理化应用提供依据。     

北部湾海产品中重金属元素的测定及评价

采集94个北部湾沿海不同区域、不同季节、不同品种的海产品,用微波消解-电感耦合等离子体质谱法测定砷、铅、汞、镉、铬、锡、锑、铜、铝等9种重金属元素的含量,以了解广西北部湾海产品是否受到重金属污染。测定结果表明,海产品中镉含量平均合格率为55%,应是污染所致,无机砷、铅、汞、铬、铜、铝含量平均合格率在89%~96%之间,受污染程度较轻,而锡、锑含量合格率为100%,未受污染。     

稻米中总砷及无机砷含量的测定与分析

采用氢化物原子荧光光度法测定13份稻米样品中的总砷和无机砷含量,结果表明：所测稻米样品中均检出总砷与无机砷,总砷含量范围为0.06~0.20 mg/kg,无机砷含量范围为0.039~0.150 mg/kg,无机砷占总砷的含量为50.0%~93.1%,无机砷含量在国家限量卫生标准以内;未冲洗大米样品中总砷含量仅为糙米的72.7%~90.0%,无机砷含量为糙米的62.7%~87.7%;多次冲洗的大米样品中总砷含量仅为未冲洗大米的75.0%~91.7%,无机砷含量为83.0%~93.6%。提高加工精度和用水淘洗均能在一定程度上降低总砷与无机砷的含量,减轻人们食用后对身体的危害。     

米糠多肽蛋白粉酶法生产新工艺研究

米糠是糙米碾白过程中被碾下的皮层,包括果皮、种皮、珠心层、糊粉层胚芽和小碎米的混合物。米糠中蛋白质含量为12～18％,几乎高出普通精米的一倍。本实验以脱脂米糠为原料,采用碱溶酸沉、复合酶（纤维素酶、风味蛋白酶、植酸酶、中性蛋白酶）酶解、活性碳脱色、真空浓缩、喷雾干燥制得米糠多肽蛋白粉。