Structure of starches extracted from near isogenic wheat lines

Differential scanning calorimetry (DSC), acidic hydrolysis and different physico-chemical approaches were used to study thermodynamic and structural characteristics of starches from near-isogenic wheat lines to establish the effect of different combinations of active granule-bound starch synthase isoforms, taking part in amylose biosynthesis, on the structure and thermodynamic properties of starches. Obtained results suggest that the effect of different GBSS I combinations is realized through altered amylose localization within starch granules, reflecting in changes of melting temperature of crystalline lamellae (T _m) and rates of acidic hydrolysis. It has also been demonstrated that changes in T _m values for native wheat starches are determined by amylose content in amylopectin clusters.     

Alkaline peroxide mechanical pulping of wheat straw with enzyme treatment

Alkaline peroxide mechanical pulping (APMP) of wheat straw with enzyme treatment was studied. Instead of direct enzyme pretreatment on wheat straw, an alternative treatment method was used, in which coarse pulps from refiner defibrated wheat straw rather than wheat straw were pretreated with a crude enzyme containing mainly xylanase, then impregnated with alkaline H₂O₂ solution and further refined. The optimum conditions of enzyme treatment were xylanase dosage of 10–15 IU/g of oven-dried wheat straw, 90 min, 50–60°C, pulp consistency of 5–10%, and initial pH of 5.0, and those for chemical impregnation were 6% NaOH, 70–80°C, 60–90 min, and 4 to 5% H₂O₂. Enzyme treatment improved pulpability of wheat straw by the APMP process, and final pulp quality such as brightness, breaking length, and burst index of pulp. Pulp from the APMP process with enzyme treatment could be bleached to a brightness of 70.5% ISO by two-stage H₂O₂ bleaching sequence with only 4% H₂O₂, and breaking length of the bleach pulp reached 4470 m.     

Structure of starches extracted from near-isogenic wheat lines

High-sensitivity differential scanning calorimetry (HSDSC) and small-angle X-ray scattering (SAXS) were used to investigate the structural characteristics of starch granules with different amylose content extracted from near-isogenic wheat lines with different combinations of active granule-bound starch synthase (GBSS I) isoforms. Paracrystalline diffraction model, ‘two-state’ model of starch melting and other physico-chemical approaches were used to estimate the sizes of amylopectin clusters, the thicknesses of crystalline lamellae and the structure of amylopectin defects for investigated wheat starches. The joint analysis of SAXS and DSC data has shown that the size of amylopectin cluster, the thickness of crystalline lamellae and the structure of amylopectin defects do not depend on the differences in combinations of active GBSS I isozymes. The data obtained supposed that the amylopectin cluster size and the thickness of crystalline lamellae are, generally, the universal structural parameters for wheat starches. Additionally, the data obtained suggest that increase of amylose content is accompanied by accumulation of both amylose tie-chains, located as defects in crystalline lamellae, and amylose chains oriented transversely to the lamella stack within amorphous lamellae. Disordered ends of amylopectin double helices and/or pre-existing double helices not participating in formation of crystals are considered as amylopectin defects arranged in crystalline lamellae. The relationship between structure of wheat starches extracted from near-isogenic lines and their thermodynamic properties was recognized.     

Comprehensive characterization of C‐glycosyl flavones in wheat (Triticum aestivum L.) germ using UPLC‐PDA‐ESI/HRMSn and mass defect filtering

A comprehensive characterization of C‐glycosyl flavones in wheat germ has been conducted using multi‐stage high resolution mass spectrometry (HRMSⁿ) in combination with a mass defect filtering (MDF) technique. MDF performed the initial search of raw data with defined C‐glycosyl flavone mass windows and mass defect windows to generate the noise‐reduced data focusing on targeted flavonoids. The high specificity of the exact mass measurement permits the unambiguous discrimination of acyl groups (nominal masses of 146, 162 and 176.) from sugar moieties (rhamnose, glucose or galactose and glucuronic acid). A total of 72 flavone C‐glycosyl derivatives, including 2 mono‐C‐glycosides, 34 di‐C‐glycosides, 15 tri‐glycosides, 14 acyl di‐C‐glycosides and 7 acyl tri‐glycosides, were characterized in wheat germ, some of which were considered to be important marker compounds for differentiation of whole grain and refined wheat products. The 7 acylated mono‐O‐glycosyl‐di‐C‐glycosyl flavones and some acylated di‐C‐glycosyl flavones are reported in wheat for the first time. The frequent occurrence of numerous isomers is a remarkable feature of wheat germ flavones. Both UV and mass spectra are needed to maximize the structure information obtained for data interpretation. Copyright © 2016 John Wiley & Sons, Ltd.     

Triazole Fungicide Residues and Their Inhibitory Effect on Some Trichothecenes Mycotoxin Excretion in Wheat Grains

Wheat is one of the global strategic crops and ranks third in terms of cereals production. Wheat crops are exposed to many fungal infections during their cultivation stages, some of which have the ability to secrete a number of toxic secondary metabolites that threaten the quality of the grains, consumer health, producer economics, and global trade exchange. Fifty-four random samples were collected from wheat which originated from different countries. The samples included 14 types of soft wheat to study the extent of their contamination with deoxynivalenol (DON) and T-2 toxin by auto-ELISA technology and r-biopharm microtiter plate. All samples were contaminated with DON toxin except one sample, and the values ranged between 40.7 and 1018.8 µg/kg⁻¹. The highest contamination rates were in Lithuanian wheat and the lowest was in Indian wheat. Meanwhile, the highest average level of T-2 toxin contamination was in Lithuanian wheat grains with 377.4 µg/kg⁻¹, and the lowest average was 115.3 µg/kg⁻¹ in Polish wheat. GC-MS/MS and multiple reaction monitoring mode (MRM) were used to detect 15 triazole derivatives in the collected samples, which may be used to combat fungal diseases on wheat during the growing season. Only 9 derivatives were found: simeconazole, penconazole, hexaconazole, cyproconazole, diniconazole, tebuconazole, metconazole, fenbuconazole, and difenoconazole. These derivatives varied according to the origin of the wheat samples as well as their concentration, whereas another 6 derivatives were not detected in any samples. A direct inverse relationship was found between the DON concentration in the samples and the residues of simeconazole, penconazole, diniconazole, tebuconazole, metconazole, fenbuconazole, and difenoconazole, and the T-2 toxin showed the same relationship except for tebuconazole. The safe and rational use of some triazole derivatives may be a new approach and a promising strategy to not only reduce plant diseases and their problems, but also to get rid of some mycotoxins as grain contaminants.     

A Multifunctional N-Doped Cu–MOFs (N–Cu–MOF) Nanomaterial-Driven Electrochemical Aptasensor for Sensitive Detection of Deoxynivalenol

Deoxynivalenol (DON) is one of the most common mycotoxins in grains, causing gastrointestinal inflammation, neurotoxicity, hepatotoxicity and embryotoxicity, even at a low quantity. In this study, a facile electrochemical aptasensor was established for the rapid and sensitive determination of DON based on a multifunctional N-doped Cu-metallic organic framework (N–Cu–MOF) nanomaterial. The N–Cu–MOF, with a large specific surface area and good electrical conductivity, served not only as an optimal electrical signal probe but also as an effective supporting substrate for stabilizing aptamers through the interactions of amino (-NH₂) and copper. Under the optimal conditions, the proposed sensor provided a wide linear concentration range of 0.02–20 ng mL⁻¹ (R² = 0.994), showing high sensitivity, with a lower detection limit of 0.008 ng mL⁻¹, and good selectivity. The sensor’s effectiveness was also verified in real spiked wheat samples with satisfactory recoveries of 95.6–105.9%. The current work provides a flexible approach for the rapid and sensitive analysis of highly toxic DON in food samples and may also be easily extended to detect other hazardous substances with alternative target-recognition aptamers.     

A Study on the Phytotoxic Potential of the Seasoning Herb Marjoram (Origanum majorana L.) Leaves

In the search of new alternatives for weed control, spices appear as an option with great potential. They are rich in bioactive natural products and edible, which might minimize toxicity hazard. Marjoram (Origanum majorana L.) is an aromatic herb that has been widely employed as a seasoning herb in Mediterranean countries. Although marjoram boasts a plethora of therapeutic properties (painkiller, antibiotic, treatment for intestinal disorders, etc.), the potential for its extracts for weed control is still to be more thoroughly explored. In order to determine their phytotoxic potential, marjoram leaves were subjected to different bioguided extraction processes, using water, ethyl acetate, acetone or methanol. The most active extract (acetone) was sequentially fractionated to identify its most active compounds. This fractionation led to the isolation and identification of 25 compounds that were classified as monoterpenes, diterpenes or flavonoids. Among them, a new compound named majoradiol and several compounds are described in marjoram for the first time. The phytotoxicity of the major compounds to etiolated wheat coleoptiles was compared against that of the commercial herbicide (Logran^®), with similar or higher activity in some cases. These results confirm the extraordinary potential of the extracts from this edible plant to develop safer and more environmentally friendly herbicides.     

应用超高效液相色谱-四极杆-飞行时间质谱法建立谷物中18种真菌毒素非靶向筛查数据库及确证方法

建立了基于超高效液相色谱-四极杆-飞行时间质谱(UPLC-Q-TOF/MS)的18种真菌毒素非靶向筛查方法。真菌毒素标准物质用HSS T3色谱柱进行色谱分离后在UPLC-Q-TOF/MS MS^E模式下分别用正、负离子模式采集,获取MS和MS/MS的信息,记录对应保留时间、加合物离子、碎片离子精确质量数等信息,设置保留时间偏移为0.3 min,加合物离子和碎片离子的精确质量匹配容差为5×10^-6,在UNIFI中建立18种真菌毒素的数据库。在稻谷、小麦基质中,以筛查检出限(SDL)作为主要参数对筛查方法进行了验证。18种真菌毒素分为有最大限量和无最大限量两种类型,结果有最大限量的真菌毒素均能在其限量水平被准确筛查,无最大限量的真菌毒素其SDL的范围为2～800μg/kg。基质效应考察表明,稻谷中有14种真菌毒素有中等基质效应,小麦中有11种真菌毒素有中等基质效应。样品经乙腈提取后用QuEChERS萃取盐包和HLB净化柱净化,用建立的方法对25批稻谷、小麦进行筛查,结果2批稻谷中检出4种真菌毒素,2批小麦中检出2种真菌毒素。该方法能准确筛查SDL水...     

短波近红外光谱的整粒小麦蛋白质PLS方法的定量分析

利用漫反射法获得的整粒小麦短波近红外光谱(833～1111nm),采用化学计量学中的偏最小二乘法(PLS)方法,选取不同的波长范围对光谱进行信息提取和分析,给出了不同因子数时PLS方法进行蛋白质分析的结果及其因子数与预测标准偏差平方和(PRESS)关系曲线,确定了最佳回归因子数。并通过选取最佳回归因子和不同波段,对整粒小麦的蛋白质成分进行了定量分析,比较了不同波长范围对分析的影响,并从中获得了较好的预测结果,实验表明,合理选择光谱范围可减少非主要信息的干扰,并以此来提高成分分析精度的方法是切实可行的,在实际应用中有一定的参考价值。     

高性能CdTe/CdS核壳型量子点的制备及应用于小麦面粉中呕吐毒素的荧光免疫检测研究

量子点荧光免疫法的广泛应用迫切需要提高量子点的发光强度和抗体的稳定性. 分别采用巯基乙酸和谷胱甘肽作稳定剂, 水相合成CdTe量子点, 再包覆CdS制备核壳型CdTe/CdS量子点. 以EDC/NHS作交联剂将CdTe/CdS量子点标记到呕吐毒素抗体上, 然后用牛血清蛋白封闭抗体. 研究发现, 谷胱甘肽稳定剂优于巯基乙酸. 与CdTe量子点相比, 谷胱甘肽修饰的CdTe/CdS量子点其荧光的强度和稳定性分别提高6倍和2倍以上. 谷胱甘肽碳链较长, 减少了量子点对抗体尤其是活性位点处的空间构型影响, 从而大大提高抗体的稳定性. 监测不同储藏时间(4 ℃)的CdTe/CdS量子点-抗体偶联复合物与呕吐毒素免疫反应前后荧光强度变化值, 结果显示抗体至少可以稳定7 d. 基于谷胱甘肽稳定的高性能CdTe/CdS量子点, 我们建立了一种新的呕吐毒素荧光免疫检测方法. 呕吐毒素浓度在0～0.9 ng•mL^－1之间相对荧光强度呈线性关系, 相关系数(R²)为0.9992, 检出限是0.038 ng•mL^－1. 方法的灵敏度高于文献报道的其它方法, 如GC-ECD, HPLC和HPLC-MS, 已成功应用于小麦面粉样品中痕量呕吐毒素的测定.