高压直流线路开路试验的控制原理及保护分析

高压直流线路开路试验是一种检测手段,主要是对换流站直流侧进行加压,其控制理念和相关保护全然不同.若控制保护异常,直流电压会异常升高或者不变,最终导致试验失败.结合常规直流系统线路开路试验,介绍了线路开路试验的控制原理,比较了理论计算与实际工程中的母线电压最大值,得出直流线路电压参考值和实际电压测量值可以同步变化,差值不超过10 kV.为了在试验不成功时闭锁换流器,采用了ABB公司Mach2系统中的电压差值保护、过流保护、过流后备保护和保护性触发等保护技术.通过保护分析得出:在原理上、工程上、保护上,直流系统的正常运行和开路试验有所不同.     

Multi‐Cereal Beverage Fermented by Lactobacillus Helveticus and Saccharomyces Cerevisiae

A novel multi‐cereal‐based fermented beverage with suitable aroma, flavor, and pH fermented by lactic acid bacteria and Saccharomyces cerevisiae was developed. Twenty‐seven lactobacilli strains were screened for acid production (pH and titratable acidity) in a mixture of malt, rice, and maize substrates. It was found that Lactobacillus helveticus KLDS1.9204 had the greatest acid production among 27 lactobacilli tested. The fermentation performance of L. helveticus KLDS1.9204 was also assayed and the fermentation parameters were optimized using Plackett–Burman design and steepest ascent method. L. helveticus KLDS1.9204 showed good proteolytic capability, however, the strain could not utilize starch. The optimum substrate consisted of 50% malt (25 g/100 mL), 25% rice (20 g/100 mL), and 25% maize (30 g/100 mL). The inoculum was 5% with a ratio of S. cerevisiae to L. helveticus KLDS1.9204 of 2.5:1. The optimum temperature was 37 °C and the time was 22 h. Lastly, the quality of the multi‐cereal‐based fermented beverage was evaluated. This beverage was light yellow, transparent, and it tasted well with a pleasant acid and a unique flavor of cereals. The beverage was rich in free amino acids and organic acids. The pH and titratable acidity of the beverage were 3.5 and 29.86 °T, respectively. The soluble solids content of the beverage was 6.5 °Brix, and the alcohol content was 0.67%.     

长鳍金枪鱼多肽制备及其对H2O2诱导的张氏肝细胞的保护作用

目的:以长鳍金枪鱼废弃物为原料提取多肽,探究其对H2O2诱导的张氏肝细胞的保护作用。方法:以H2O2诱导张氏肝细胞损伤建立细胞模型组,以相对增殖率为指标筛选长鳍金枪鱼废弃物最适酶种,通过正交试验确定最佳酶解条件。酶解产物经超滤、阴离子交换色谱、凝胶过滤色谱和反相高效液相色谱方法纯化分离得到多肽,用噻唑蓝(MTT)比色法对其每步分离效果进行评价。多肽活性的评价是利用试剂盒方法测定张氏肝细胞上清液中AST、ALT、MDA、ADH和SOD的含量,倒置显微镜观察细胞形态及流式细胞仪检测多肽对H2O2诱导后的张氏肝细胞凋亡的影响。结果:最适酶种为胰蛋白酶,最佳酶解条件为料液比1∶3(g/mL),pH 9,加酶量900 U/g,温度45℃,时间5 h。经一系列纯化后制成多肽,命名为长鳍金枪鱼多肽。其氨基酸序列为Gly-Ala-Pro-Gly-Glu-Arg-Gly-Ser-Lys-Cys-Phe-Lys。经长鳍金枪鱼多肽作用于H2O2诱导的张氏肝细胞后,ALT、AST、ADH和MDA含量下降,SOD含量上升。通过流式细胞仪检测发现晚期凋亡细胞相比于模型组减少明显。结论:利用酶解方法提取的长鳍金枪鱼多肽对H2O2损伤的张氏肝细胞具有一定的保护作用。     

改性玉米醇溶蛋白对速冻水饺质量的影响

以大豆分离蛋白(SPI)为原料,分别采用碱性蛋白酶、胰蛋白酶、风味蛋白酶对SPI进行酶解,测定水解度及ACE抑制率,结果表明碱性蛋白酶酶解液效果较好.采用响应曲面法对碱性蛋白酶酶解工艺参数进行优化,在此基础上采用双酶协同酶解和三酶联合酶解,然后对酶解液进行超滤分离和真空冷冻干燥,采用FA-Phe-Gly-Gly为底物的酶活力检测法对不同大豆降压肽组分进行活性检测.结果表明三酶联合酶解效果最好,水解度(DH)及ACE抑制率高达32.24％和84.44％.     

The Glycemic Potential of White and Red Rice Affected by Oil Type and Time of Addition

Limited research exists on how different oil types and time of addition affect starch digestibility of rice. This study aimed to assess the starch digestibility of white and red rice prepared with 2 oil types: vegetable oil (unsaturated fat) and ghee (clarified butter, saturated fat) added at 3 different time points during the cooking process (“before”: frying raw rice in oil before boiling, “during”: adding oil during boiling, and “after”: stir‐frying cooked rice in oil). Red rice produced a slower digestion rate than white rice. White rice digestibility was not affected by oil type, but was affected by addition time of oil. Adding oil “after” (stir‐frying) to white or red rice resulted in higher slowly digestible starch. Red rice cooked using ghee showed the lowest amount of glucose release during in vitro digestion. The addition of ghee “during” (that is boiling with ghee) or “before” (that is frying rice raw with ghee then boiling) cooking showed potential for attenuating the postprandial glycemic response and increasing resistant starch content. This is the first report to show healthier ways of preparing rice. White rice with oil added “after” (stir‐fried) may provide a source of sustained glucose and stabilize blood glucose levels. Boiling red rice with ghee or cooking red rice with ghee pilaf‐style may provide beneficial effects on postprandial blood glucose and insulin concentrations, and improve colonic health. The encouraging results of the present study justify extending it to an in vivo investigation to conclusively determine the effect of time of addition of fat when rice is cooked on blood glucose homeostasis.     

Preparation and characterisation of films from xylose‐glycosylated peanut protein isolate powder

This work aimed at producing and characterising xylose‐glycosylated peanut protein isolate (PPI‐X) films by dissolving PPI‐X powder in water at ambient temperature and further plasticising with glycerol. The effect of powder dissolution temperature (20–100 °C) and glycerol concentration (15.0–45.0%, w/w) on mechanical properties and integrity of these films was quantified. The results showed that the powder dissolution temperature had no significant effect on the mechanical and water resistance properties of PPI‐X films within the temperature range tested. With increasing concentration of glycerol, the tensile strength and water resistance of PPI‐X films decreased and elongation increased. The films produced by dissolving the PPI‐X powder at 20 °C and plasticising with 25.0% glycerol had comparable mechanical properties and better water resistance compared to some other plant protein films plasticising with glycerol. The results suggested that PPI‐X films could potentially be used as biodegradable packaging materials.     

Authenticity green coffee bean species and geographical origin using near-infrared spectroscopy combined with chemometrics

To prevent the adulteration of agricultural resources and provide a solution to enhance the green coffee bean supply chain, authentication using the near-infrared spectroscopy (NIRS) technique was investigated. Partial least square with discrimination analysis (PLS-DA) models combined with various preprocessing methods were built from NIR spectra of 153 Vietnamese green coffee samples. The model combined with the standard normal variate and the first order of derivative yielded excellent performance in predicting coffee species with the error cross-validation of 0.0261. PLS-DA model of mean centre and first-order derivative spectra also yielded good performance in verifying geographical indication of green coffee with the error of 0.0656. By contrast, the predicting abilities of post-harvest methods were poor. The overall results showed a high potential of the NIRS in online authentication practices.     

《食品机械与设备》教学方法改革的探索与实践

根据长期《食品机械与设备》课程的教学研究及实践,发现教学中存在不足,影响该课程的教学效果;本文提出着重从改革前导课程教学、激发学生的兴趣、丰富教学内容、加强与改革实践教学环节、培养学生的自学能力、改革教学方法手段等六个方面分析了改革《食品机械与设备》教学方法的心得.     

方便米粉微波干燥特性的研究

本试验使用160、320、480、640和800 W的微波功率对方便米粉进行干燥,研究了方便米粉的微波薄层干燥特性,并采用8个常用的薄层干燥数学模型对试验数据进行拟合。结果表明:方便米粉的微波干燥过程可分为加速、恒速、降速3个阶段。Midilli-Kucuk模型具有较高的拟合度,能够较好的描述和预测样品干燥特性。通过Fick扩散模型计算出方便米粉微波干燥的有效扩散系数在1.44×10~(-9)~6.42×10~(-9)m~2/s之间。     

超临界流体分离大豆磷脂酰胆碱

研究了超临界流体CO2 /乙醇分离大豆磷脂酰胆碱的影响因素。结果表明 :在温度 4 0℃- 6 0℃ ,压力在 15MPa - 2 5MPa ,乙醇浓度在 2 % - 2 0 %之间 ,较低的温度 ,较高的压力和较高的乙醇浓度有利磷脂酰胆碱含量的提高。在温度 4 0℃、压力 2 5MPa、乙醇浓度 15 % (v/v)下 ,磷脂酰胆碱含量可达 89% (TLC扫描法 )