Peptide with angiotensin I-converting enzyme inhibitory activity from hydrolyzed corn gluten meal

Corn gluten meal (CGM) was hydrolyzed by Alcalase after starch removal of CGM was applied as a pretreatment. A new inhibitory peptide for angiotensin I-converting enzyme (ACE) was isolated from the hydrolysate of CGM with the use of Bio-Rad P-2 gel filtration and followed by reverse-phase high-performance liquid chromatography (RP-HPLC). The sequence of the active peptide was determined to be Ala-Tyr after the application of amino acid analysis and HPLC/MS. The IC50 of the peptide was 14.2 microM, and it was not affected by preincubation with 30 mU of ACE at 37 degrees C for 3 h. Ala-Tyr also exerted antihypertensive effects after oral administration to spontaneously hypertensive rats. A maximal reduction of systolic blood pressure of 9.5 mmHg was observed 2 h after oral administration of Ala-Tyr at doses of 50 mg/kg.     

玉米黄粉可降解性塑料的制备和性质

玉米黄粉是湿法玉米淀粉加工的副产物。为充分利用这种副产物生产可降解塑料,将其与增塑剂甘油混合后,经单螺杆挤压机制成母粒,母粒再被热压成型为试验片,并对试验片的性质进行了分析,结果表明：含有20%甘油的试验片具有良好的机械性质;以Halsey方程为基础,建立的模型能预测试验片拉伸强度与相对湿度关系,经验证模型与实际测量值具有良好的拟合性;应用扫描电子显微镜观察试验片内部结构的结果表明它具有均匀的结构;热重分析的结果表明可降解试验片在170℃以下时能保持热稳定性。     

电子束辐照技术提高玉米蛋白粉酶解效果

为了研究玉米蛋白粉的酶解关键技术和利用电子束辐照技术辅助提高玉米蛋白粉的酶解效果,该研究以蛋白质质量分数为79.4%的玉米蛋白粉为原料,以水解度(degree of hydrolysis,DH)和1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picryl-hydrazyl,DPPH)清除率为衡量指标,借助单因素和响应面试验设计方法,在优选碱性蛋白酶可控酶解制备玉米抗氧化肽的最佳工艺参数基础上,研究了不同辐照剂量的电子束辐照处理对玉米蛋白粉酶解效果的影响,并利用场发射扫描电镜检测技术分析电子束辐照前后玉米蛋白粉表面形态的变化。研究发现:当碱性蛋白酶的酶解温度为50℃、酶解p H值为8.6、酶与底物浓度比为9.13%时,玉米蛋白粉的水解度可达40.26%±0.23%;所制备的玉米抗氧化肽的DPPH清除率为70.74%±0.41%;若采用辐照剂量为3.24 k Gy进行电子束辐照处理玉米蛋白粉时,则其水解度可达到49.17%±0.42%,其DPPH清除率可达73.03%±1.02%;经场发射扫描电镜检测分析得知,被辐照处理后的玉米蛋白粉表面凹凸程度增加,完整性下降。研究结果可为玉米精深加工产业和玉米抗氧化肽的深入研究提供理论参考。     

用谷朊粉溶涨指数法测定谷朊粉品质

开发了一种新的谷朊粉品质检测方法。对小麦谷蛋白溶涨指数法的参数进行调整，在9种不同离心力条件下，测定从16个小麦品种中分离出的谷朊粉的溶涨指数，根据谷朊粉溶涨指数、面筋吸水率及面粉的蛋白质组分含量之间的关系，提出了用谷朊粉溶涨指数法测定谷朊粉品质的步骤及评价标准。结果认为：加入0.9 mL蒸馏水水化10 min，再加入0.9 mL 0.3%十二烷基磺酸钠(SDS)－乳酸溶液混合30 min，最后用5000×g离心力进行离心是谷朊粉品质测定的最佳技术参数，在此条件下的谷朊粉溶涨指数与面筋吸水率、小麦谷蛋白溶涨指数呈显著正相关(r＝0.541，0.547；P<0.05)，与面筋指数、不溶性谷蛋白含量呈极显著正相关(r＝0.608，0.589；P<0.01)，与单体蛋白含量呈显著负相关(r＝-0.573；P<0.05)。与测定谷朊粉品质的国家标准方法吸水率法相比，谷朊粉溶涨指数法能快速、稳定地反应小麦谷朊粉品质差异。     

沙蒿籽粉和谷朊粉对燕麦全粉食品加工品质的影响

为了探讨全燕麦粉面包、馒头加工品质及燕麦粉冷冻面团品质特性,以燕麦全粉为原料,研究了添加沙蒿籽和谷朊粉对燕麦全粉食品(含冷冻面团食品)加工品质改良效果。试验结果表明,谷朊粉对面包制作影响较大;沙蒿籽粉对馒头制作影响较大;沙蒿籽粉和谷朊粉共同使用的效果优于两者单独使用;加入2.5%沙蒿籽粉和8%谷朊粉对燕麦全粉面包和馒头品质改善效果最好。对冷冻面团加工而言,随着冷冻时间的延长面团品质不断下降,冻藏4 d后燕麦全粉冷冻面团面包、馒头品质显著降低。     

Colorimetric determination of alkaline phosphatase as indicator of mammalian feces in corn meal: collaborative study

In the official method for rodent filth in corn meal, filth and corn meal are separated in organic solvents, and particles are identified by the presence of hair and a mucous coating. The solvents are toxic, poor separation yields low recoveries, and fecal characteristics are rarely present on all fragments, especially on small particles. The official AOAC alkaline phosphatase test for mammalian feces, 44.181-44.184, has therefore been adapted to determine the presence of mammalian feces in corn meal. The enzyme cleaves phosphate radicals from a test indicator/substrate, phenolphthalein diphosphate. As free phenolphthalein accumulates, a pink-to-red color develops in the gelled test agar medium. In a collaborative study conducted to compare the proposed method with the official method for corn meal, 44.049, the proposed method yielded 45.5% higher recoveries than the official method. Repeatability and reproducibility for the official method were roughly 1.8 times more variable than for the proposed method. The method has been adopted official first action.     

Mineral dialyzability in milk and fermented dairy products fortified with FeNaEDTA

Iron, zinc, and calcium dialyzability and ascorbic acid (AA) concentrations were evaluated in milk and yogurt fortified with FeNaEDTA (FE) or ferrous sulfate (FS) as a control, with or without AA addition. The values obtained for FE iron dialyzability in milk were much higher than those obtained for FS. The addition of AA to milk improved Fe dialyzability when using FS and slightly decreased Fe dialyzability in the FE-fortified nonfermented samples. Milk fermentation increased iron availability from both iron sources. Zinc and calcium dialyzability in products containing any of the two iron sources was increased in fermented milks. EDTA improved Zn dialyzability from intrinsic zinc in every manufactured dairy product. Whereas for milks fortified with FS and stored at 4 degrees C for 24 h, the AA content remained close to the original concentration, a higher AA degradation was observed when milks were fortified with FE.     

Survey of vitamin content of fortified milk

This paper summarizes work done by 4 different laboratories on the vitamin content of milk. Riboflavin, vitamin A, and vitamin D were assayed in whole, 2%, and skim milks that had been fortified. In general, the adherence to label claim decreased with decreasing fat content. This may be due to methods and stage of vitamin addition prior to processing.     

International mycotoxin check sample program: Part I. Report on laboratory performance for determination of aflatoxins B1, B2, G1, and G2 in raw peanut meal, deoiled peanut meal, and yellow corn meal

Three aflatoxin-contaminated samples (raw peanut meal, deoiled peanut meal, and yellow corn meal) were analyzed by 121 laboratories in 31 countries. Sufficient data were obtained to permit a statistical comparison of the performance of laboratories using the BF, CB, and EEC methods and those using high performance liquid chromatography (HPLC) for quantitation. No significant differences were found between means for laboratories using these 4 methods for the analysis of raw peanut meal or yellow corn meal. However, for deoiled peanut meal, means were significantly different for laboratories using the BF method compared with the CB or EEC methods for B1 and B2, and for laboratories using the CB method compared with HPLC methods for G2.     

Cyclopiazonic acid production by cultures of Aspergillus and Penicillium species isolated from dried beans, corn meal, macaroni, and pecans

Ninety-five isolates of Aspergillus and Penicillium species from selected dried foods were examined for their ability to produce cyclopiazonic acid (CPA). The isolates were grown in sterile synthetic liquid medium at 28 degrees C for 8 days in the dark. The medium and mold mycelia were then extracted with chloroform. CPA was semiquantitatively determined by thin layer chromatography through visual comparison with standards. The cultures of A. flavus were also examined for their ability to produce aflatoxin. One A. tamarii and all 13 P. urticae isolates produced CPA, whereas only 19 of the 31 (61%) A. flavus isolates produced CPA, and 6 (19%) A. flavus produced aflatoxin. All 13 P. urticae isolates also produced patulin and griseofulvin. CPA-producing A. flavus was found in all food types but not in all samples. CPA-producing P. urticae was found only in dried beans and macaroni.     

New brine saturation technique for the extraction of light filth from rubbed sage, paprika, and corn meal: intralaboratory study.

A new and widely applicable technique for the isolation of light filth from food has been developed. It includes a simple alcohol defatting followed by a brine saturation of the product by heating and cooling and a subsequent trapping of the filth elements with olive oil and tap water. The methods circumvent the use of hazardous and expensive solvents and lengthy defatting and/or pre-treatment procedures. In an intralaboratory study, recoveries of elytral squares and rodent hair fragments added to paprika, rubbed sage, and corn meal ranged from 95.8 to 100%.     

Properties of aged montmorillonite-wheat gluten composite films

The properties of new and aged glycerol-plasticized vital wheat gluten films containing < or =4.5 wt % natural or quaternary ammonium salt modified montmorillonite clay were investigated. The films were cast from pH 4 or pH 11 ethanol/water solutions. The films, aged for < or =120 days, were characterized by tensile testing, X-ray diffraction, and transmission electron microscopy. In addition, water vapor permeability (11% relative humidity) and the content of volatile components were measured. The large reduction in the water vapor permeability with respect to the pristine polymer suggests that the clay platelets were evenly distributed within the films and oriented preferably with the platelet long axis parallel to the film surface. The film prepared from pH 11 solution containing natural clay was, as revealed by transmission electron microscopy and X-ray diffraction, almost completely exfoliated. This film was consequently also the strongest, the stiffest, and the most brittle and, together with the pH 11 film containing modified clay, it also showed the greatest decrease in water vapor permeability. The large blocking effect of the clay had no effect on the aging kinetics of the films. During aging, the pH 4 and pH 11 film strength and the pH 4 film stiffness increased and the pH 4 film ductility decreased at the same rate with or without clay. This suggests that the aging was not diffusion rate limited, that is, that the loss of volatile components or the migration of glycerol or glycerol/wheat gluten phase separation was not limited by diffusion kinetics. The aging rate seemed to be determined by slow structural changes, possibly involving protein denaturation and aggregation processes.     

Glass transition of wheat gluten plasticized with water, glycerol, or sorbitol

The glass transition temperature of wheat gluten, plasticized with water, glycerol, or sorbitol, has been studied using dynamical mechanical thermal analysis. For the three plasticizers studied, the general behavior of the glass transition temperature broadly followed the Couchman-Karasz relation using a wheat gluten DeltaC(p)() of 0.4 J g(-)(1) K(-)(1). Compared on such a fractional weight basis, it could be concluded that the plasticizing effect of glycerol and sorbitol on wheat gluten proteins is less important than the plasticizing effect of water. A continuous curve was obtained with the three plasticizers when the evolution of the glass transition temperature was presented on a fractional molecular basis. This was related to the similar chemical structure of these three components containing hydroxyl groups.     

Liquid chromatographic determination of vitamin D in fortified milk

A method for the determination of vitamins D2 + D3 in fortified milk is described. Vitamins D2 and D3 are extracted from the saponified sample and converted to isotachysterols with antimony trichloride. The isotachysterols are quantitated using liquid chromatography with ultraviolet detection at 301 nm, which is the absorption maximum. At this wavelength other materials present in the sample do not interfere with the analysis of isotachysterols and therefore a cleanup step is avoided. Recoveries of vitamin D added to skim milk were 98.1% (SD 5.3), 96.7% (SD 3.3), and 96.0% (SD 5.1) for samples fortified with 200, 400, and 600 IU/quart, respectively. For whole milk, recoveries were 102.0% (SD 6.5) and 97.1% (SD 3.5) in samples fortified with vitamin D equivalent to 200 and 400 IU/quart, respectively. The detection limit for vitamin D is 40 IU/quart.     

秸秆合成气合成甲醇的动力学研究

为了实现农业废弃物转化为化工产品（燃料甲醇）,有效地利用生物质能,在直流流动等温积分反应器中,采用C301铜基催化剂, 催化剂粒度0.175 mm×0.147 mm,在压力为5 MPa,反应温度220～270 ℃,质量空速15532.67～26343.47 NL/（kgcat?h）条件下,对秸秆合成气合成甲醇动力学进行了研究。用Langmuir-Hinshelwood本征动力学模型和改进的高斯－牛顿法确定了该反应的动力学参数。残差分析和统计检验结果表明,所得到的本征动力学模型方程与试验数据吻合良好,为生物质（秸秆）气制备甲醇中试研究及甲醇合成反应器的设计提供了参考。     

直线形围栏陷阱系统对玉米地鼠情的监测效果

围栏陷阱(trap-barrier system,TBS)技术自2008年起在我国许多省市进行应用性试验和推广,已有的研究多是注重防治效果,虽有多位作者设想该技术还可用于鼠情监测,但尚少见针对性试验和全面的数据支持。为研究直线形围栏陷阱系统(linear trap-barrier system,L-TBS)用于农田鼠情监测的科学依据,探索L-TBS所获鼠情资料与常规性夹夜法的对应关系,2015年5—10月在新疆博乐市玉米地进行了两种方法监测效果的对比试验。通过同一区域、不同地点、操作方式一致的3组重复试验,L-TBS监测的农田害鼠种类、种群数量动态与繁殖特征,皆与夹夜法结果吻合:鼠种组成百分比卡方检验,小家鼠x~2=1.50,灰仓鼠x~2=0.54,均小于X20.01;两种方法的繁殖特征相关性检测,性比r=0.710 0,怀孕率r=0.926 8,睾丸下降率r=0.869 2,繁殖指数r=0.940 0,均显著正相关。而L-TBS因能捕获幼体而更全面反映种群年龄结构;L-TBS还能捕获夹夜法难以捕获的鼩鼱,可用于防疫监测。由L-TBS法(X)与夹夜法(Y)获得的优势种小家鼠捕获率极显著正相关,回归方程y=0.143 1+0.146 5x(d.f.=42,r=0.707 7,P=0.000 0),展示了其与夹夜法的关联性。研究证明:在6.67 hm2农田边设置60 m长的L-TBS可以达到鼠害防治与监测的目的,比常规夹夜法具更省工、省力、安全,具有可操作性强的优点;而L-TBS比矩形TBS更便于机械化农事操作,适于农田推广应用。     

差速式玉米种子脱粒机的性能试验

为优化差速式玉米种子脱粒机脱粒系统的有关参数,进而降低玉米种子在脱粒过程中的损伤,该文采用二次回归正交旋转组合设计的方法,以籽粒破碎率为主要性能指标,选取直辊转速、喂入量、籽粒含水率为试验因素,对差速式玉米种子脱粒机进行了性能试验。分析结果表明：籽粒含水率对破碎率的影响呈二次函数关系,籽粒含水率太大或太小,对籽粒破碎率的影响都很大;喂入量越小,籽粒破碎率就越小,当喂入量低于0.9 kg/s时,籽粒破碎率稳定,基本不受喂入量的影响;直辊转速越小,籽粒破碎率就越小;直辊转速、籽粒含水率和喂入量对籽粒破碎率的交互影响也很显著,当籽粒含水率在18%,喂入量在0.9 kg/s,直辊转速在200 r/min时,籽粒破碎率取得最小值。研究成果对进一步研究玉米种子的差速脱粒原理、优化脱粒系统参数、开发低损伤脱粒工艺具有重要的意义。     

农田不同肥力条件下玉米秸秆腐解效果

为了探讨农田不同肥力对玉米秸秆腐解转化和能态变化的影响,该文采用砂滤管法在陕西关中高、中等、低3种肥力塿土上进行了480 d的玉米秸秆腐解试验,研究了腐解进程中玉米秸秆的分解率以及有机碳组成和能态变化。结果显示,随着腐解进行,腐解产物中的苯–醇溶性、水溶性组分下降,半纤维素和纤维素含量先上升后下降,而木质素增加;腐解物的能态呈现上下起伏、下降和相对稳定3个阶段的变化,总体是一个放能过程。腐解产物的热值与其有机碳、苯–醇溶性组分、水溶性组分、半纤维素和纤维素呈显著正相关,但与其灰分、木质素、腐殖物质含量呈显著负相关。腐解480 d,3种肥力间比较发现,玉米秸秆在中等肥力田块上矿化率最高,低肥力田块上的最低;中等肥力土壤能够促进玉米秸秆中的水溶性有机组分和木质素的分解,而高肥力土壤能够促进苯–醇溶性组分和半纤维素、纤维素分解,并有利于腐殖物质的形成,而且腐解物的能态最高。