Soybean Trypsin Inhibitor Assay: Further Improvement of the Standard Method Approved and Reapproved by American Oil Chemists’ Society and American Association of Cereal Chemists International

For measuring trypsin inhibitor (TI) activities in soybean products, the current standard method, approved and reapproved by American Oil Chemists Society (Method Ba 12-75) and American Association of Cereal Chemists International (Method 22-40.01), features mixing trypsin with a series of inhibitor levels and then adding a substrate to start the colorimetric reaction. Yet, previous studies have shown flaws with the method, particularly with using several inhibitor levels and the sequence of adding the substrate last. The present study showed that with varying levels of dilution and volumes of a dilute sample extract, the pH of the premix (the mixture of a dilute sample extract and trypsin solution) ranged 3.30–3.60 for raw soy flour, and 3.20–6.70 for toasted soy. Within these premix pH ranges, the standard method of adding substrate last would give TI values equal to or less than those measured by the same method except for adding the enzyme last. The standard method was subsequently improved by using a single sample extract level and the enzyme-last sequence. Other modifications included making stock solutions for reagents, adding Ca²⁺ to the trypsin solution, diluting sample extracts to a level that causes 30–70% of inhibition, and running both reference and sample blanks for better controls. Alternatively, the full volume assay (10 mL total, as in the standard method) was further modified by using half the volume of each reagent with the same concentration. Compared to the standard method, the improved methods gave more consistent results when assaying 11 selected soy products. The half volume (5 mL) and full volume methods gave the same results, but the former could increase assay sensitivity and reduce amounts of reagents used.     

我国鲜食玉米标准体系及营养标准研究

近年来我国鲜食玉米产业发展迅猛, 但同时也暴露出诸多产业乱象。梳理现有鲜食玉米标准体系是促进产业标准化、规范化的重要举措。本文通过对我国现行鲜食玉米标准进行梳理, 总结出目前我国鲜食玉米标准体系中抽样及一般性检测标准较完善、技术规程体系成熟、标准体系框架已建立的特点; 同时提出我国鲜食玉米标准体系存在技术规程标准内容重复、品质分级标准混乱、缺乏营养评价指标相关标准、感官评价标准混乱、缺乏甜糯玉米和笋玉米的相关标准、标准体系结构不合理等的问题; 并针对上述问题提出对应应统一技术规程标准, 建立营养评价体系, 统一品质分级标准, 统一感官评价指标, 完善甜糯玉米和笋玉米相关标准的解决办法。为鲜食玉米标准体系的建设及规范化提供参考和建议。     

影响食品检测方法标准实施有效性的风险分析及对策

食品检测为食品安全监管提供技术支撑，是确保食品安全的关键一环，最严谨的标准需要在实验室中科学有效的应用才会更好地服务于最严格的监管。本文主要分析了影响实验室食品检测方法标准实施有效性的因素，剖析了检测过程中人、机、料、法、环、测6个方面可能存在的风险因子，通过风险识别、风险分析评价和风险应对，确保检测方法有效实施和检测数据准确可靠，为监管机构和社会大众提供客观、公正和科学的依据。     

脱硫胶粉在乳化改性沥青中的应用

考察了不同规格胶粉及不同脱硫程度的脱硫胶粉对橡胶改性乳化沥青性能的影响,结果表明,采用100目胶粉即可制备出橡胶改性乳化沥青,但乳化沥青的性能较差;采用活化度为50%左右的100目脱硫胶粉制备乳化沥青时,脱硫胶粉的用量相比于胶粉可大幅提高;在通过外掺100目50%左右活化度的脱硫胶粉(质量分数15%,以沥青计,下同)和质量分数2%的苯乙烯-丁二烯-苯乙烯嵌段共聚物改性的乳化沥青中添加质量分数1%的丁苯胶乳,所制备橡胶改性乳化沥青无筛上剩余物,5 d储存稳定性为2.9%,蒸发残留物的25℃针入度、软化点和5℃延度分别为55 (0.1 mm)、64.5℃和22.5 cm,能够满足乳化改性沥青的技术指标要求。     

云花皱织物的设计与开发

设计与开发了云花皱织物。络筒工序以"高车速、小张力、降毛羽、提产量"为工艺原则;整浆联合工序以"高车速、贴伏毛羽、减磨兼顾增强"为工艺原则;银丝不上浆,按照色经排列要求放在相应的伸缩筘中,并控制好张力;银丝和黑色花式线应穿在规定的综框;织造工序以"高车速、大张力、早开口"为工艺原则。经过对织造准备工序和织造工序的优化使得织造效率达到90%以上,下机一等品率达到93%,入库一等品率达到99%。     

优化气相色谱法测定生活饮用水中六六六和滴滴涕

目的优化GB/T 5750.9-2006《生活饮用水标准检验方法农药指标》中的气相色谱法测定生活饮用水中六六六(α-666、β-666、γ-666、δ-666)和滴滴涕(ρ,ρ'-DDE、ο,ρ'-DDT、ρ,ρ'-DDD、ρ,ρ'-DDT)含量。方法样品经石油醚萃取浓缩后,经由电子捕获检测器-气相色谱测定α-666、β-666、γ-666、δ-666、ρ,ρ'-DDE、ο,ρ'-DDT、ρ,ρ'-DDD、ρ,ρ'-DDT的含量。结果 8种组分在8 min内全部出峰,各物质在5～100.0μg/L浓度范围内线性关系良好,相关系数均大于0.999,检出限为0.007～0.010μg/L,回收率为85.10%～105.85%,相对标准偏差为0.43%～2.68%。结论该方法分离效果高,灵敏度高,重复性好,准确度高,可以满足实验室条件下水样中六六六和滴滴涕的测定。     

Spatial filtering velocimeter using frequency shifting by the method of rotating kernel

A new approach of frequency shifting by rotating kernel is proposed to improve the performance of a spatial filtering velocimeter, used to provide accurate velocity information for a vehicle self-contained navigation system. A linear CMOS image sensor was employed both as a spatiotemporal differential spatial filter and as a photodetector. The filtering operation was fully performed in FPGA and is realized by applying a rotating kernel to the pixel values of the image. Theoretical analysis showed this method could double the maximum measurable velocity. The power spectrum of the output signal was obtained by fast Fourier transform (FFT), and was corrected by a frequency spectrum correction algorithm, named energy centrobaric correction. This velocimeter was used to measure the moving velocities of a conveyor belt. Experimental results verified the method’s ability of reducing the output signal frequency and standard uncertainty of velocity measurement. What is more, the undesired output introduced by frequency shifting to the power spectrum of the output signal was deeply investigated and a new method was proposed to eliminate the undesired component in output signals. This velocimeter aims at providing accurate velocity information for vehicle autonomous navigation system.     

A comparison study into low leak rate buoyant gas dispersion in a small fuel cell enclosure using plain and louvre vent passive ventilation schemes

Hydrogen, producing electricity in fuel cells, is a versatile energy source, but with risks associated with flammability. Fuel cells use enclosures for protection which need ventilating to remove hydrogen emitted during normal operation or from supply system leaks. Passive ventilation, using buoyancy driven flow is preferred to mechanical systems. Performance depends upon vent design, size, shape, position and number. Vents are usually plain rectangular openings, but environmentally situated enclosures use louvres for protection. The effect of louvres on passive ventilation is not clear and has therefore been examined in this paper. Comparison ‘same opening area’ louvre and plain vent tests were undertaken using a 0.144 m³ enclosure with opposing upper and lower vents and helium leaking from a 4 mm nozzle on the base at rates from 1 to 10 lpm, simulating a hydrogen leak. Louvres increased stratified level helium concentrations by typically in excess of 15%. The empirical data obtained was also used in a validation exercise with a SolidWorks: Flow Simulation CFD model, which provided a good qualitative representation of flow behaviour and close empirical data correlations.     

Performance of the LDA Volumetric Flow Rate Standard Under Severely Disturbed Flow Conditions

Flow meters in thermal power plants are operated at high temperatures and pressures and often encounter disturbed flow profiles. This leads to an increased measurement uncertainty, limiting the safe operating range of flow rates and thus, the plant's power output. To respond to this shortcoming, the laser optical flow rate standard (LFS) was developed. The LFS is designed to allow the on-site calibration of industrial flow meters in power plants at high temperatures and pressures. It makes use of the laser Doppler anemometry (LDA), as a fundamental and non-invasive method, to measure the velocity field simultaneously with two LDA systems. The volumetric flow rate is then determined by means of integration. Here, we present flow rate measurements for a fully developed pipe flow and for six pipe diameters downstream of a disturbance generator. The mean deviation in flow rate between the two LDA systems was 0.05%, with a mean deviation from the gravimetric reference flow rate of 0.12%. The highest deviations from the reference were 0.21% and 0.31%, for the first and second system respectively.