添加改性纳米SiO2对芳纶纸性能的影响

采用4种不同用量的硅烷偶联剂KH-550对纳米SiO₂表面进行改性,并检测改性后纳米SiO₂粒径的大小;研究了改性后纳米SiO₂的添加量对芳纶纸性能的影响;通过扫描电镜(SEM)观察添加改性纳米SiO₂后芳纶纸的表观形貌,并将纳米SiO₂添加前后纸张抗张强度和介电强度进行了对比。结果表明,随着硅烷偶联剂用量的增加,改性纳米SiO₂的粒径有所减小;当纳米SiO₂与硅烷偶联剂KH-550配比为5 g∶20 mL、改性纳米SiO₂添加量为5%时,芳纶纸的抗张强度提高了66.2%,硅烷偶联剂用量的增加对纸张伸长率有一定影响,其紧度变化不明显;SEM图显示改性纳米SiO₂粒子填充在纸张空隙处利于纸张性能的增强;添加改性纳米SiO₂较未添加纳米SiO₂和添加未改性纳米SiO₂芳纶纸的抗张强度和介电强度均有所提高。     

巯基改性磁性介孔二氧化硅的制备及其对重金属Cd2+的吸附研究

以稻壳灰为硅源、Fe3O4为磁性材料制备磁性介孔二氧化硅(MMS);随后对其进行巯基改性制备巯基改性磁性介孔二氧化硅(TMMS),并考察了搅拌时间、反应温度、氨水添加量对TMMS表面巯基浓度的影响,研究了巯基浓度对Cd~(2+)吸附效果的影响;最后,对MMS与TMMS的结构进行表征,并通过吸附等温线对MMS与TMMS对Cd~(2+)吸附效果进行比较。结果表明:当反应时间8 h、水浴温度80℃、催化剂氨水添加量750μL时,TMMS的表面巯基浓度达到0.131mmol/g;巯基浓度越高,TMMS对Cd~(2+)的吸附效果越好;MMS与TMMS两种材料的骨架均为无定形的SiO2结构,BET多点比表面积分别为581.769 m2/g与405.665 m2/g;MMS与TMMS对Cd~(2+)的等吸附温模型更符合Langmuir模型,都属于单分子层吸附;在Langmuir模型中,TMMS的饱和吸附量为33.33 mg/g,大于MMS的饱和吸附量(21.50 mg/g)。因此,巯基改性有利于TMMS对Cd~(2+)的吸附,可达到有效脱除废水中Cd~(2+)的目的。     

黄曲霉毒素B1污染玉米的比重筛分研究

研究比重法对AFB_1污染玉米的筛分效果。结果表明:风量、纵向倾角和振幅对比重筛分效果具有显著影响(P0.05),且在风量为6 000m~3/h、倾角7°、振幅15mm时,不同污染程度的玉米经比重筛分后,相比原料中的AFB_1含量,重质玉米中AFB_1含量分别降低21.2%和38.4%,轻质玉米和破碎率比例适中。比重筛分机是中国粮食生产中的重要设备,通过比重筛分去除AFB_1污染严重玉米具有良好的应用前景。     

有机改性蒙脱土吸附黄曲霉毒素B1能力的研究

利用十八烷基三甲基溴化铵(OTMAB)作为有机改性剂对钠基蒙脱土(Na-MMT)进行改性,以提高对黄曲霉毒素B1(AFB1)的吸附能力。改性后的钠基蒙脱土利用X-射线衍射(XRD)、傅立叶变换红外光谱(FTIR)、扫描电镜(SEM)及热失重分析(TGA)等方法对其结构特性进行研究。结果表明,改性剂OTMAB插入到钠基蒙脱土的夹层内并扩大了其夹层间距(d_(0.01)),增大了其比表面积。改性蒙脱土对AFB1的吸附等温线符合Langmuir数学模型。有机改性Na-MMT对AFB1的最大吸附量(q_(max))为34.25 mg/g,Langmuir吸附常数(k)为3.65L/mg,均高于未改性的Na-MMT(q_(max)=28.74mg/g和k=2.37L/mg),说明有机改性能够有效提高Na-MMT对AFB1的吸附能力。     

木质纤维基碳量子点/介孔TiO2复合体系的构建及光催化性能的研究

本研究以氮掺杂酶解玉米芯残渣碳量子点(E-N-CQDs)和介孔TiO_2进行复合,构建了介孔TiO_2/E-N-CQDs复合光催化剂体系,对其进行了分析表征,并探讨了其对水相中亚甲基蓝(MB)的降解能力。结果表明,E-N-CQDs具有良好的荧光性能,且其表面羧基、氨基等发色基团和助色基团增强了其荧光特性;介孔TiO_2具有较大的比表面积,孔径8～32 nm;与介孔TiO_2相比,光照300 min时,介孔TiO_2/E-N-CQDs对MB的降解率达到89%,提高了59%。由此可见,碳量子点的加入可显著提高介孔TiO_2的光催化降解能力,提高了对可见光的利用率。     

气象、样品属性等因素与花生油中黄曲霉毒素B1污染水平关联性分析

目的 以2017—2018年广东省市售花生油中黄曲霉毒素B₁（AFB₁）的污染状况为例,分析特定因素对AFB₁污染的影响。方法 采集2017—2018年广东省21个地市637份花生油样品,记录其样品标签属性,并根据GB 5009.22—2016《食品中黄曲霉毒素B族和G族的测定》中的高效液相色谱-柱后衍生法测定样品中AFB₁含量。结合第五代欧洲中期天气预报中心全球气候大气再分析数据库（ERA5）获得的样品产地气象数据计算样品生产前1个月的平均数据,并分析其与AFB₁含量关联性。结果 广东省2017—2018年市售花生油中AFB₁总检出率为65.3%,超标率为24.6%。其中,定型包装花生油样品无超标,而散装花生油样品有较高的超标率,且AFB₁含量中位数显著高于定型包装样品。在多个气候因素中“花生油生产前1个月的平均气温水平”与散装包装样品AFB₁的超标率和含量有较强的关联,其中生产前平均气温超过25 ℃的散装包装样品AFB₁含量中位数约为气温低于22 ℃样品的3.5倍。然而其他气候因素并未展现出与AFB₁含量的相关性。结论 2017—2018年广东地区散装花生油样品AFB₁具有较高的超标率,而花生油生产前1个月平均气温是影响其AFB₁含量的重要因素。建议对广东省散装花生油的生产环境、生产方式进行重点关注并提高花生油质量,以减少居民AFB₁等危险因素的暴露风险。     

食用植物油中过氧化值和黄曲霉毒素B1调查

通过检测食用油的过氧化值、黄曲霉毒素B₁,了解餐饮业食用油的使用情况。方法 在市县地区采集具有代表性的样品共150个,过氧化值按照GB/T 5009.37—2003方法检测,黄曲霉毒素B₁ 按照GB/T 5009.23—2003方法检测。结果 过氧化值合格率为100%,黄曲霉毒素B₁检测情况为:煎炸油合格率91.7%,花生油合格率89.3%,调和油、菜籽油、大豆油、棕榈油合格率100%。煎炸油、花生油黄曲霉毒素B₁检测值范围为1.00～21.6 μg/kg、0.80～40.4 μg/kg。结论 食用油的原料质量要严格管控,防止污染,杜绝黄曲霉毒素B₁的产生。     

纳米SiO2颗粒对油水分离滤纸性能的影响

本研究以正硅酸乙酯(TEOS)和甲基三乙氧基硅烷(MTES)为前驱体,采用溶胶-凝胶法制备出表面带有疏水基团甲基(—CH3)的纳米SiO_2颗粒。将制备的纳米SiO_2颗粒与阳离子苯丙乳液共混浸渍滤纸,制备出一种油水分离滤纸。实验通过改变TEOS和MTES的配比制备出不同的纳米SiO_2颗粒,探讨了不同的纳米SiO_2颗粒对油水分离滤纸的表面微观结构、静态接触角和油水分离效率的影响。研究结果表明,当TEOS与MTES配比为4∶3的纳米SiO_2颗粒用量为1. 0%时,油水分离滤纸对水的静态接触角达到148. 4°,对十六烷和水的混合油品的分离效率达到99. 8%。此时,油水分离滤纸的透气度相比于仅用乳液浸渍的滤纸下降了7. 7%。     

碳量子点/银复合材料用于食用油中黄曲霉毒素B1的检测

采用原位复合法制备出高效复合的碳量子点/银复合材料(CDs/Ag),研究了黄曲霉毒素B_1(AFB_1)对CDs/Ag荧光强度的影响。结果表明:AFB_1与CDs/Ag溶液相互作用后,体系的荧光强度增强,由此建立测定食用油中AFB_1的新方法。在p H 7.6的硼酸-硼砂缓冲溶液中,CDs/Ag和AFB_1在25℃反应30 min时,体系荧光强度(F)与AFB_1质量浓度(c)呈良好线性关系,线性范围为0.01~0.8μg/m L,线性方程为F=1 902c+309.3,R~2为0.998 4,检出限为7.4×10~(-3)μg/m L。采用该方法测定了食用油中AFB_1的含量,回收率为95%~106%。     

电子束辐照降解玉米中黄曲霉毒素B1及对玉米品质的影响

为考察电子束辐照对玉米中黄曲霉毒素B_1(aflatoxin B_1,AFB_1)的降解效果及对玉米品质的影响,试验选取AFB_1污染的玉米为原料,研究0~50kGy剂量辐照下玉米中AFB_1的降解效果,并考察电子束辐照对玉米理化性质,包括脂肪酸值、黏度值和色度的影响。结果表明,随着电子束辐照剂量的升高(5~50kGy),玉米中AFB_1含量显著降低(P0.05);当电子束辐照剂量大于15kGy时,玉米理化性质变化较明显,其中脂肪酸值显著升高(P0.05),黏度值显著下降(P0.05),L*值无显著变化(P0.05),a*,b*值显著下降(P0.05)。     

Kinetic modelling of aflatoxins B1 conversion and validation in corn,rice, and peanut during thermal treatments

A kinetic model of the aflatoxins B₁ conversion was plotted and validated successfully in the aflatoxin B₁-contaminated rice during thermal treatments. Specifically, the kinetic Model A and Model B of the aflatoxin B₁ conversion were plotted based on the differential-scanning calorimetry and thermogravimetric analysis, respectively, with the pure aflatoxin B₁. In succession, Model A and Model B were validated in the aflatoxin B₁-contaminated corn, rice, and peanut during thermal treatments. Model A successfully simulated the conversion of aflatoxin B₁ in the aflatoxin B₁-contaminated rice with the correlation coefficients of 0.859 and average-absolute deviation of 6.61. The activation energy and conversion order of the aflatoxin B₁ conversion were 89.0 kJ/mol and 0.12, respectively. Moreover, the relationships between the conversion degree and time vs temperature were plotted based on Model A. These plots would help to predict the final content of aflatoxin B₁ after thermal treatments, and give an instruction to develop a food processing.     

稻壳灰二氧化硅(RHAS)的制备、表征及在菜籽油脱胶中的应用

利用农业生产的副产物稻壳为原料,制备了比表面积大、结构细的稻壳灰SiO₂(RHAS),同时采用EDX、FTIR、XRD、SEM、N₂吸附-脱附对RHAS进行了表征与分析,并以RHAS为脱胶剂,考察RHAS对菜籽油的脱胶效果。结果表明:RHAS颗粒大小均匀、结构疏松,BET比表面积达149cm²/g; RHAS对菜籽油中的磷脂有较强的吸附脱除作用,在脱胶温度50℃、脱胶剂用量4. 5%、脱胶时间40 min条件下,脱胶率可达57. 8%,且再生循环6次脱胶,脱胶率仍达35%左右。RHAS可作为一种良好的新型植物油吸附脱胶剂。     

Aflatoxin B1-degrading activity from Bacillus subtilis BCC 42005 isolated from fermented cereal products

ABSTRACT

Aflatoxin B₁ is a naturally occurring mycotoxin that is produced as secondary metabolite by Aspergillus spp., especially A. flavus and A. parasiticus. This is the most severe toxin due to its carcinogenic, mutagenic, and teratogenic properties. Hence, methods for toxin degradation have been received increasing interest from both scientific communities and industries. In this study, 32 isolates of Bacillus spp. from various fermented cereal products were screened for their aflatoxin B₁ degradation ability. The results indicated the extracellular fraction of Bacillus subtilis BCC 42005 isolated from Iru (African locust bean) potentially possessed aflatoxin B₁-degrading ability. The maximum activity of the active fraction was at 50°C and pH 8.0. The activity was stable in a wide range of pH (5.0–8.0) and temperature (25–60°C). The aflatoxin B₁-degrading mechanisms of this strain may be possibly involved by enzyme(s). This extracellular fraction was not toxic at IC₅₀ 4 mg/ml and it can be combined with water as a soaking agent for maize, which results in 54% of aflatoxin B₁ reduction after contact time 120 min. Hence, the extracellular fraction of Bacillus subtilis BCC 42005 can be further applied as an effective soaking agent in a pretreatment process with a practical and easy-to-implement condition and also probably used to reduce the aflatoxin B₁ contamination in other foods and feeds commodities.     

Aflatoxin B1 and sterigmatocystin survey in beer sold in China

ABSTRACT

A total of 101 samples of beer from the Chinese market were analysed for the presence of aflatoxin B₁ (AFB₁) and sterigmatocystin (STC), using methods based on liquid chromatography–tandem mass spectrometry. The limit of quantification and the limit of detection in beer were 0.1 and 0.03 µg/kg, respectively. Recoveries of AFB₁ and STC from spiked beer samples were 97.8–103.6% and 92.7–102.1%, respectively. None of the beer purchased samples were contaminated with AFB₁ or STC.     

Fungi and natural incidence of selected mycotoxins in barley rootlets

The storage of barley rootlets is increasingly employed to provide raw material for pig feeding in Brazil. Barley rootlets represent an important feedstuff for animal production due to their high levels of protein and fiber, and low price. However, poor management of raw materials during storage can result in fungal growth, the loss of nutritive substances and contamination by mycotoxins. The aims of this work were (1) to identify fungi associated with barley rootlets used as pig feedstuff raw material, and (2) to identify and quantify selected mycotoxins naturally produced by isolated mycotoxin-producing species in this substrate over a year. Samples were examined for fungal counts and genera distribution. Fumonisin B₁ and aflatoxin B₁ contamination were determined using high pressure liquid chromatography (HPLC). Barley rootlet samples were of low hygienic quality. Although a broad survey was undertaken, low fungal diversity was found. Fusarium verticillioides was the most prevalent species followed by Aspergillus flavus. Despite Aspergillus clavatus being widely associated with high-moisture sprouted grains including brewers’ grains, and causing toxicity to livestock, it was not detected in this work. Although pre-harvest contamination of the barley crop, as in the maize, could occur, the barley might support F. verticillioides/Fusarium proliferatum growth when grain is remoistened during the germination and malting process and it might even continue during storage on pig farms. All samples were positive for fumonisin B₁ whereas aflatoxin B₁ contamination was not detected. It is important to point out the potential risk of fumonisin contamination in barley rootlets used as animal feed. Fusarium toxins are important not so much for their acute effects as for the chronic syndromes reported worldwide. The obtained results reveal the need for periodic monitoring of raw materials to avoid problems in animal production and hazards to animal and human health.     

Aflatoxin B1 in sesame seeds and sesame products from the Greek market

Aflatoxin B₁ (AFB₁) is considered as the most potent liver carcinogen for humans. A method for determination in sesame seeds was developed. AFB₁ was extracted by methanol-water, cleaned by immunoaffinity columns and determined by high-performance liquid chromatography with fluorescence detection. The recovery factor and the limit of detection (LOD) of AFB₁ in sesame seeds were 111.5% and 0.02 ng g^?1, respectively. Thirty samples of sesame products were examined for the presence of AFB₁. After analysis, 77.6% of samples were found to be contaminated. Eight samples exceeded the European Union (EU) limit (2 µg AFB₁ kg^?1). In 15 samples, AFB₁ was below the EU limit. Seven samples remained below the LOD. The most contaminated (14.49 ng AFB₁ g^?1) sample was unpeeled packaged sesame seeds. In all samples, aflatoxigenic Aspergilli fungi as well as the risk for AFB₁ presence in sesame seed was investigated.     

介孔二氧化硅制备固定化菠萝蛋白酶的研究

采用经扫描电镜和透射电镜表征的介孔二氧化硅制备固定化菠萝蛋白酶,具有工艺简便、条件温和及操作方便的特点。考察了给酶量、pH和时间对固定化菠萝蛋白酶活力的影响,在酶量25mg/mL、pH5.0、固定化时间22h时,固定化酶的酶活为603U/g。介孔二氧化硅固定的菠萝蛋白酶在50℃水浴60min后,固定化酶的活力保持在92%以上,说明固定化酶的热稳定性较高。该固定酶持续操作三次后,使用活性逐渐衰减,但第3次相对酶活仍然达38.5%,反映了菠萝蛋白酶分子与载体有较强的物理吸附作用而且固定的菠萝蛋白酶有一定的可重复使用性。      

Aflatoxin B1 and sterigmatocystin in wheat and wheat products from supermarkets in China

Wheat is an important cereal but it is often contaminated with mycotoxins. The natural occurrence of aflatoxin B₁ (AFB₁) and sterigmatocystin (STC) was determined in 178 food samples (32 wheat samples and 146 wheat products) purchased from Chinese supermarkets. The methodology was validated, the wheat and wheat products samples were treated with a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) and quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). From these samples 18.8% of wheat and 8.2% of cracker samples were contaminated with AFB₁. Mean levels were 0.06 µg/kg and 0.05µg/kg, respectively. There was no AFB₁ contamination in white bread or whole meal bread. Meanwhile 53.1% of wheat, 59.2% of crackers, 20.8% of white bread and 16% of whole meal bread samples were contaminated with STC. The mean levels were 0.07, 0.79, 0.12 and 0.12 µg/kg respectively. Although the levels were low, this demonstrates the need for more comprehensive surveys for these two mycotoxins in wheat and wheat products from China.     

微波辅助碱法降解黄曲霉毒素工艺对无毒米蛋白品质的影响

研究了微波辅助碱法降解黄曲霉毒素B1(AFB1)优化工艺对米蛋白品质的影响。研究表明,在单位体积微波功率750 W/L条件下,随着微波处理时间(0.2、3.1、5.6、7.2和8.6 min)的延长,微波辅助碱法制备无毒米蛋白的回收率及纯度的变化不显著,溶解性、起泡性和持油性显著提高,起泡稳定性、乳化性及乳化稳定性先提高后下降,而持水性呈下降趋势。因此,该工艺不仅能确保米蛋白产品安全无毒,还可提高米蛋白的部分品质。