不同加工精度对稻谷中镉含量的影响

为了解不同加工精度的稻谷中镉含量的差别,利用砻谷机、碾米机将46组稻谷分别制成糙米、四级精米、三级精米、二级精米、一级精米,三级糠粉和一级糠粉;用原子吸收分光光度计测定46组稻谷各组分的镉含量并进行分析,得出镉含量的大小顺序为:三级糠粉一级糠粉糙米四级精米三级精米二级精米一级精米;通过将稻谷中各组分两两比较进行配对样本T检验,得出一级糠粉与糙米的镉含量差异显著(P0.05),其余稻谷组分的镉含量比较分析具有较大差异性(P0.01);不同加工精度的精米中重金属镉含量也存在显著差异:四级精米镉含量最高,为(0.40±0.24) mg/kg,一级精米镉含量最低,为(0.22±0.13) mg/kg;糙米在镉限量值0.2 mg/kg范围附近时,被加工成一级精米后镉含量降低了一半左右;稻谷的糠层对镉的富集作用最强,对于整个稻米镉含量分析有较大影响。     

稻谷在碾米加工中镉的含量和分布研究

采用浙江省收获的自然污染镉的稻谷样品为材料,通过实验室砻谷和碾米得到糙米、加工精度为三级的大米、糠粉等组成成分,并利用微波消解,石墨炉原子吸收光谱法测定镉的含量并进行比较,分析糙米在碾白加工前后镉含量变化和分布情况。结果表明:糙米加工成大米的精米率平均为90.46%,而糠粉所占的比例平均为9.22%,大米和糠粉中镉的含量与糙米中镉的含量有显著的相关性,糙米碾白后制得的大米,镉含量有显著降低,平均为糙米中含量的94.81%;糠粉中镉含量则显著升高,平均是糙米的144.84%。留存在大米中的镉的总量占糙米的85.75%,留存在糠粉中镉的总量占糙米的13.36%。通过碾白将糙米制成大米,能降低可食用部分的镉含量,但总量降低幅度不大。     

稻谷中镉元素残留分布特征分析

收集一定数量受镉污染的稻谷样品,通过砻谷机、碾米机和旋风磨粉机等仪器,将稻谷样品制成糙米、糠粉,精米及稻壳等样品,采用原子吸收分光度计石墨炉法,参照国家标准<食品中的镉的测定>分别测定上述样品中的镉含量,分析稻谷中镉元素的分布特征,探讨能否通过深加工的方式降低稻谷的镉含量,使加工后大米满足<粮食卫生标准>规定的稻谷(包括大米)的镉污染限量要求.     

稻谷在加工过程中无机砷含量的分布情况

目的 测定糙米、大米及糠粉中无机砷的含量, 研究无机砷在稻米中的分布情况。方法 随机抽取20份稻谷样本, 经实验室垄谷和碾米后得到的糙米、大米及糠粉。使用液相色谱-原子荧光联用仪检测所得糙米、大米及糠粉中的无机砷含量。结果 样本中的砷主要以亚砷酸根[As(Ⅲ)]的形式存在。糙米中的亚砷酸根[As(Ⅲ)]含量为(0.122±0.45) mg/kg, 经过碾白后, 其含量显著降低(P<0.05), 为(0.068±0.02) mg/kg, 米糠样本中的亚砷酸根[As(Ⅲ)]含量显著高于其他2个样本(P<0.05), 达到(0.604±0.201) mg/kg。结论 稻米中的无机砷主要以亚砷酸盐[As(III)]形式存在, 糙米经过碾米加工后可以显著降低砷的含量。     

稻谷加工工艺对产品镉含量的影响

研究稻谷加工工艺(砻谷、碾米)与稻谷镉去除率的关系,明确通过砻谷、碾米工艺获得大米镉含量达标的可能性,为制定镉超标稻谷的加工利用技术提供科学依据。以不同镉含量的稻谷为材料,通过砻谷、碾米获得不同加工精度的大米;使用微波消解-石墨炉原子吸收光谱法检测其镉含量,分析稻谷在砻谷、碾米过程中镉含量的动态变化。结果表明:1)稻谷经砻谷加工后镉含量降低;镉含量低于0.226 mg/kg的稻谷,通过砻谷获得镉含量达标(0.2 mg/kg)的糙米。2)碾米加工可降低大米的镉含量,当碾米精度为23.83%时对镉的去除效果最佳;镉含量低于0.288 mg/kg的糙米,通过碾米获得镉含量达标的大米。3)镉含量高于0.323 mg/kg的稻谷,应考虑其他加工途径去除或降低大米或产品的镉含量。     

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。     

基于稻谷X射线荧光光谱测定快速识别糙米和精米中的镉含量

目的 基于稻谷镉的X射线荧光光谱测定, 建立糙米、精米镉的快速定量识别模型, 简化入仓稻谷重金属检测的砻谷、碾米等预处理步骤。方法 采用X射线荧光光谱法一一对应分析26组稻谷-糙米-精米样品中镉含量。根据线性、对数、逆、二次、三次、幂、指数等函数关系分别拟合稻谷-糙米、稻谷-精米、糙米-精米镉含量之间的回归模型。采用另外4组样品对决定系数(r2)大于0.95的模型准确性进行验证, 根据决定系数、误差值等筛选最优拟合模型。结果 稻谷-糙米-精米镉含量之间存在较强的相关性, 在此基础上建立的3个可食用米镉含量快速识别模型分别为: 稻谷-糙米三次函数回归模型Y=0.0131+0.7178X+0.5722X2-0.3492X3 (R2=0.9859); 稻谷-精米三次函数回归模型Y=0.0284+0.3779X+1.5500X2-1.2046X3 (r2=0.9855); 糙米-精米幂函数回归模型Y=0.9412×X1.0233 (r2=0.9902), 三个模型预测结果的绝对误差分别为8.91%、8.57%和10.24%。结论 本研究建立的回归模型具有良好的稻米镉含量相互预测性能, 该法有望简化稻谷镉检测前的砻谷、碾米等预处理流程, 提高检测效率。     

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。     

应用近红外光谱技术快速测定粳稻品种的直链淀粉含量

应用近红外光谱法以稻谷、糙米、精米、糙米粉和精米粉为扫描材料分别建立了粳稻直链淀粉含量的预测模型。结果表明采用光谱预处理的校正效果比不采用预处理的好,用偏最小二乘法(PLS)获得的粳稻稻谷、糙米、精米、糙米粉、精米粉的回归模型和交叉验证结果为:最优校正决定系数(R2)和交叉检验均方误差(RMSECV)分别为0.8136、2.74,0.8864、2.56,0.8915、2.59,0.9261、2.26,0.9505、1.83,粉碎性样品的误差比整粒样品的误差小。育种实践中,低世代可选用糙米、高世代可选用糙米粉或精米粉作为扫描样本测定稻米直链淀粉含量。     

用近红外光谱技术快速测定籼稻品种的蛋白质含量

分别以稻谷、糙米、精米和精米粉为扫描材料,应用近红外光谱法建立了籼稻蛋白质含量的预测模型.结果表明,采用光谱预处理的校正效果比不采用预处理的好,用偏最小二乘法(PLS)获得的籼稻稻谷、糙米、精米、精米粉的回归模型和交叉验证结果为:最优校正决定系数(R2)和交叉检验均方误差(RMSECv)分别为0.772 1、0.507,0.888 4、0.379,0.911 6、0.336,0.951 0、0.258,稻谷的误差最大,粉样的误差最小.育种实践中,低世代可选用糙米、高世代可选用精米和精米粉作为扫描样本测定稻米蛋白质含量.     

Total mercury and methylmercury in Chinese rice and dietary exposure assessment

ABSTRACT

Total mercury levels and methylmercury levels were investigated for various grain parts (whole rice, rice husk, brown rice, polished rice, and bran) of 507 rice samples from 15 main rice-producing areas of China. The average total mercury contents in brown rice samples and polished rice samples were 4.2 and 3.3 μg/kg, respectively, the percentages exceeding the national standard limit were 0.59% and 0.39%, respectively. The average methylmercury levels were 2.9 and 2.4 μg/kg in brown rice and polished rice, respectively. The order of total mercury contents in different parts of rice was bran > brown rice > whole rice > rice husk > polished rice, and the order for methylmercury was bran > brown rice > whole rice > polished rice > rice husk. Total mercury intakes and methylmercury intakes were estimated for the Chinese population and the associated health risks were assessed.     

Evaluation of physicochemical properties of enzyme treated brown rice (Part B)

A novel processing technology is developed to polish rice in a more selective way with the help of xylanase and cellulase enzymes of microbial sources. Selective degradation of bran layers has facilitated the retention of vital nutrients and non-nutrient phytochemicals. Antioxidative property of brown rice (PUSA Basmati), its milled fraction and enzyme treated brown rice is evaluated. The overall order of antioxidant activity is brown rice > enzyme treated rice > milled rice. Enzymatic treatment resulted in an increase in water uptake ratio, volume expansion ratio with reduced cooking time over brown rice. Unlike the mechanically milled rice, where great losses are incurred in nutrients and head rice yield, bio-polished rice is produced with better cooking and nutritional attributes.     

Comparative studies on major nutritional components of black waxy rice with giant embryos and its rice bran

The concentration of nutrients in brown rice is mainly associated with embryo size. Various beneficial components have been purified from rice bran. Recently developed black waxy rice with a giant embryo (‘Milyang 263’, BGE), which is the ge ^t mutant of the GE gene, was selected and analyzed to produce high quality nutritional components. γ-Aminobutyric acid (GABA) content in BGE rice bran, one of the most important nutritional compounds in rice, showed a 10.6-fold increase (2.66±0.48 mg/g) compared to that of BGE brown rice (0.25±0.01 mg/g). In addition, brown rice and BGE rice bran showed enriched amylopectin (94.5±0.5 and 97.0±0.0%) and bioactive anthocyanin [Cy-3-G: 75.15±4.18 (brown rice), 82.97±0.81 (rice bran) and Pn-3-G: 1.52±0.50 (brown rice), 4.33±0.20 (rice bran); mg/100 g] contents. These results suggest that BGE rice bran can be used as an excellent raw material to efficiently produce high quality essential amino acids, cyanidin-3 glycoside-enriched anthocyanins, and GABA.     

Rice kernel phenolic content and its relationship with antiradical efficiency

Plant phenolics exert beneficial effects on human health and may also prevent oxidative deterioration of food. Two field experiments were carried out for characterising phenolics in rice. The first assay was conducted in 1999 and 2000 in Beaumont, TX and included five light‐brown, two purple and 10 red pericarp coloured cultivars. ‘Bran colour’ was highly statistically significant for both bran phenolic concentration and antiradical efficiency (p < 0.001). ‘Year’ and its interaction with bran colour were not significant for the analysed traits, suggesting that seasonal differences and their interactions may not affect phenolic content or antiradical efficiency. The accessions ranged from 3.1 to 45.4 mg gallic acid equivalents (GAE) g^?1 bran and from 10.0 to 345.3 µM trolox equivalents (TE) g^?1 bran for total phenolic content and antiradical efficiency respectively. The light‐brown bran genotypes exhibited the lowest values for phenolic content and antiradical efficiency, whereas red bran ones displayed ca 10 times higher total phenolic content and more than 50 times higher tannin content than light‐brown ones. The two purple lines showed either low or high values for the studied traits. Antiradical efficiency of rice bran extracts was highly positively correlated with total phenolic content (r = 0.99***), suggesting that phenolics are the main compounds responsible for the free radical‐scavenging activity in rice bran extracts. In the second field experiment (Stuttgart, AR, 2001 and Beaumont, TX, 2000), 133 coloured rice cultivars were analysed for total phenolic content in whole grain. The accessions showed a large variation for total phenolics, ranging from 0.69 to 2.74 mg GAE g^?1 grain. The data confirmed previous results suggesting bran colour as the main factor affecting phenolic concentration in rice kernel and seasonal effects and their interactions as not significant. The results also confirm that within red and purple bran groups can be found the highest phenolic concentrations in rice kernel. Published in 2004 for SCI by John Wiley & Sons, Ltd.     

Genotypic variation of iron partitioning in rice grain

The present study investigates the variation of Fe concentration and partitioning in different grain tissues, particularly in the endosperm (white rice) among different rice cultivars from diverse genetic backgrounds. Iron concentration ranged from 10 to 20 mg kg^?1 in brown rice and 3–11 mg kg^?1 in white rice. Iron concentration in white rice was not correlated with that in brown rice. Polishing removed 25–84% of Fe from the brown rice, resulting in a low Fe concentration in the white rice and changed the ranking order for Fe concentration among the cultivars tested. Total Fe content in the whole grain including husk (r = 0.28, NS) and total Fe content in brown rice (r = 0.09, NS) was not significantly correlated with Fe concentration in white rice. Iron content in white rice was found to vary between 0.05 and 0.2 µg grain^?1 among cultivars tested, with the highest Fe content in cv. Sakha. Iron concentration in white rice was negatively correlated with total Fe content in the bran fraction, which is lost during the polishing process to produce white rice from brown rice (r = ? 0.82**). The partitioning of Fe between the endosperm and bran seemed to play a key role in achieving high Fe concentration in the white rice. The surface cell layers of the caryopsis appeared to be the main resistance of Fe partitioning into the endosperm (white rice) as there was a significantly negative correlation between Fe concentration in the white rice and Fe content in the bran, which is lost during the polishing process. Copyright © 2007 Society of Chemical Industry     

不同浸泡工艺改良糙米品质的研究

分别采用清水浸泡和复合酶浸泡糙米,在单因素实验的基础上,利用正交实验分析法,确定了最佳清水浸泡糙米的工艺条件:料液比1∶1.6,温度40℃,时间50 min,此条件下糙米的吸水率达到(15.18±0.60)％;最佳复合酶浸泡糙米的工艺条件:pH 5.0,温度50℃,时间50 min,复合酶质量浓度0.4 g/L,酶配比...     

Correlation of tocopherol,tocotrienol, γ-oryzanol and total polyphenol content in rice bran with different antioxidant capacity assays

The relationship between antioxidant capacity and levels of various antioxidants in rice bran and brown rice powder was evaluated. Three different varieties of Venezuelan rice, namely, Cimarrón, Zeta 15 and FONAIAP-1, were studied using ferric reducing antioxidant power (FRAP), 2,2′-azinobis-3-ethylbenzotiazoline-6-sulphonic acid (ABTS), and oxygen radical absorbance capacity (ORAC) to measure antioxidant capacity. The results showed that rice varieties contained different levels and combinations of total polyphenols, γ-oryzanol, α- and γ-tocopherols and α-, γ- and δ-tocotrienols. Compared to brown rice powder, rice bran contained most of the antioxidants and had correspondingly higher values of antioxidant capacity. Principal components analysis and multiple regression on the data indicate that FRAP was sensitive to polyphenols and total tocotrienols, while ORAC was sensitive to polyphenols and total tocopherols. ABTS was the least sensitive of all assays tested. Thus, results from antioxidant capacity assays must be interpreted with caution particularly in complex systems and that further study is necessary to define more precisely the nature of the relevant chemical reactions.     

富氢水发芽糙米加工工艺及其品质研究

本研究利用富氢水（HRW）加工发芽糙米,以富氢水浓度、发芽温度和浸泡时间为主要影响因素,以发芽势、发芽率和总黄酮含量为考核指标,在利用单因素和响应面试验建立和优化发芽工艺条件的基础上,进一步分析富氢水对糙米米糠超微结构及部分热物性参数的影响。结果表明,富氢水加工发芽糙米的最佳工艺条件为:浸泡时间13 h、发芽温度29 ℃、富氢水浓度1.5 mg/L,在此条件下糙米发芽势为67%、发芽率为84%、总黄酮含量为186.5 mg/100 g,极显著（P<0.01）高于普通纯水发芽糙米的发芽势（46%）、发芽率（70%）及总黄酮含量（130.3 mg/100 g）;此外,与普通纯水处理相比,富氢水发芽糙米米糠结构更疏松;发芽糙米糊化热焓值显著（P<0.05）低于未发芽糙米及普通纯水发芽糙米。表明利用富氢水加工发芽糙米可有效提高发芽效率、改善糙米功能活性及糊化特性,具有较好的转化应用价值。     

全脂米糠膳食纤维化挤压及可溶性工艺技术研究

为了探索全脂米糠粉挤压规律,以纤维素酶为催化剂,利用双螺杆挤压机做生化反应器对全脂米糠粉进行了挤压试验研究,获得了具有不同膳食纤维含量的挤出物。在单因素研究的基础上,采用了五元二次正交旋转组合设计(1/2)实施研究了机筒温度、螺杆转速、物料水分、加酶量和模孔直径对挤出物膳食纤维含量的影响规律。结果表明:5个因素对膳食纤维得率的影响大小依次为水分(X2)机筒温度(X4)pH值(X1)酶添加量(X3)螺杆转速(X5)。在pH值6.5、水分39%、加酶量3.5%、转速110r/min和机筒温度125℃条件下,所得全脂米糠粉中膳食纤维产率为33.51%。可溶性膳食纤维含量为9.9%。