Arabinogalactan proteins are incorporated in negatively charged coffee brew melanoidins     

Bekedam EK  De Laat MP  Schols HA  Van Boekel MA  Smit G 《Journal of agricultural and food chemistry》2007,55(3):761-768

The charge properties of melanoidins in high molecular weight (HMw) coffee brew fractions, isolated by diafiltration and membrane dialysis, were studied. Ion exchange chromatography experiments with the HMw fractions showed that coffee brew melanoidins were negatively charged whereas these molecules did not expose any positive charge at the pH of coffee brew. Fractions with different ionic charges were isolated and subsequently characterized by means of the specific extinction coefficient (K(mix 405nm)), sugar composition, phenolic group content, nitrogen content, and the arabinogalactan protein (AGP) specific Yariv gel-diffusion assay. The isolated fractions were different in composition and AGP was found to be present in one of the HMw fractions. The AGP accounted for 6% of the coffee brew dry matter and had a moderate negative charge, probably caused by the presence of uronic acids. As the fraction that precipitated with Yariv was brown (K(mix 405nm) = 1.2), compared to a white color in the green bean, it was concluded that these AGPs had undergone Maillard reaction resulting in an AGP-melanoidin complex. The presence of mannose (presumably from galactomannan) indicates the incorporation of galactomannans in the AGP-melanoidin complex. As the uronic acid content in the more negatively charged melanoidin-rich, AGP-poor HMw fractions decreased, it was hypothesized that acidic groups are formed or incorporated during melanoidin formation.  相似文献   

Near-threshold inelastic collisions using molecular beams with a tunable velocity     

Gilijamse JJ  Hoekstra S  van de Meerakker SY  Groenenboom GC  Meijer G 《Science (New York, N.Y.)》2006,313(5793):1617-1620

Molecular scattering behavior has generally proven difficult to study at low collision energies. We formed a molecular beam of OH radicals with a narrow velocity distribution and a tunable absolute velocity by passing the beam through a Stark decelerator. The transition probabilities for inelastic scattering of the OH radicals with Xe atoms were measured as a function of the collision energy in the range of 50 to 400 wavenumbers, with an overall energy resolution of about 13 wavenumbers. The behavior of the cross-sections for inelastic scattering near the energetic thresholds was accurately measured, and excellent agreement was obtained with cross-sections derived from coupled-channel calculations on ab initio computed potential energy surfaces.  相似文献   

Diurnal patterns in dispersal of Monilinia fructigena conidia in an apple orchard in relation to weather factors     

Finian Bannon  Gerrit Gort  Gerard van Leeuwen  Imre Holb  Mike Jeger 《Agricultural and Forest Meteorology》2009,149(3-4):518-525

The aerial concentration of Monilinia fructigena (causing brown rot in pome fruit) conidia was sampled during 1997 and 1998 in an apple orchard and was related to weather conditions. The highest hourly concentration measured in 1997 was 230 conidia/m³, in 1998 concentrations were lower than in 1997 throughout the season. In both years concentrations were highest in the afternoon hours. Generalised linear models, employing a Poisson distribution for the spore counts and a logarithm link function, were used to study the relationships between spore counts and lagged weather variables. In 1997 the best fitting model had variables temperature lagged at 100 h, an east–west component of wind direction, and wind speed; whereas in 1998 the best model included in addition an effect of relative humidity. Temperature and wind direction had consistent effects on hourly spore counts in both years, but whereas temperature has a biologically relevant effect on spore production and maturation, the effect of wind direction is likely to reflect the purely local effect of orchard layout. Results are compared with observations made in stone fruit orchards where Monilinia laxa and Monilinia fructicola are the predominant species, and differences in epidemiology between these systems are discussed.  相似文献   

Optimizing Parameters of CSM-CERES-Maize Model to Improve Simulation Performance of Maize Growth and Nitrogen Uptake in Northeast China   总被引：1，自引：0，他引：1  

LIU Hai-long  YANG Jing-yi  HE Ping  BAI You-lu  JIN Ji-yun  Craig F Drury  ZHU Ye-ping  YANGXue-ming  LI Wen-juan  XIE Jia-gui  YANG Jing-min  Gerrit Hoogenboom 《中国农业科学(英文版)》2012,(11):1898-1913

  相似文献   

Isolation and characterization of undenatured chlorogenic acid free sunflower (Helianthus annuus) proteins   总被引：1，自引：0，他引：1  

González-Pérez S  Merck KB  Vereijken JM  van Koningsveld GA  Gruppen H  Voragen AG 《Journal of agricultural and food chemistry》2002,50(6):1713-1719

A method for obtaining sunflower protein (SFP) isolate, nondenatured and free of chlorogenic acid (CGA), has been developed. During the isolating procedure, the extent of CGA removal and protein denaturation was monitored. The defatted flour contained 2.5% CGA as the main phenolic compound. Phenolic compounds were removed by aqueous methanol (80%) extraction, before protein extraction at alkaline pH and diafiltration. Differential scanning calorimetry and solubility tests indicated that no denaturation of the proteins had occurred. The resulting protein products were biochemically characterized, and the presence of protein-CGA complexes was investigated. SFPs of the studied variety were found to be composed of two main protein fractions: 2S albumins and 11S globulins. In contrast to what has been previously reported, CGA was found to elute as free CGA, not covalently associated to any protein fraction.  相似文献   

Effects of non-covalent interactions with 5-O-caffeoylquinic acid (chlorogenic acid) on the heat denaturation and solubility of globular proteins     

Prigent SV  Gruppen H  Visser AJ  Van Koningsveld GA  De Jong GA  Voragen AG 《Journal of agricultural and food chemistry》2003,51(17):5088-5095

The non-covalent interactions between the monomeric phenolic compound chlorogenic acid (5-CQA) and bovine serum albumin (BSA), lysozyme, and alpha-lactalbumin were characterized, and their effect on protein properties was examined. 5-CQA had a low affinity for all three proteins, and these interactions seemed to show a negative cooperativity. 5-CQA-BSA binding decreased with increasing temperature, whereas pH (pH 3.0 compared to pH 7.0) and ionic strength had no pronounced effect. At high 5-CQA/protein molar ratios, both the denaturation enthalpy and temperature of BSA increased; however, covalent bonds were created at high temperatures. The presence of 5-CQA had no effect on the solubility of BSA and alpha-lactalbumin as a function of pH, whereas it decreased lysozyme solubility at alkaline pH due to covalent interactions. These results indicate that the non-covalent interactions with 5-CQA do not have pronounced effects on the functional properties of globular proteins in food systems.  相似文献   

Development of a biocatalytic process for the production of c6-aldehydes from vegetable oils by soybean lipoxygenase and recombinant hydroperoxide lyase   总被引：4，自引：0，他引：4  

Noordermeer MA  Van Der Goot W  Van Kooij AJ  Veldsink JW  Veldink GA  Vliegenthart JF 《Journal of agricultural and food chemistry》2002,50(15):4270-4274

Volatile C6- and C9-aldehydes and alcohols are widely used as food flavors to reconstitute the "fresh green" odor of fruits and vegetables lost during processing. To meet the high demand for natural flavors, an efficient, cheap, and versatile biocatalytic process was developed to produce C6-aldehydes on a large scale. Vegetable oils were converted by soybean lipoxygenase and recombinant hydroperoxide lyase into hexanal and (2E)- or (3Z)-hexenal. In contrast to plant extracts, generally used as enzyme sources, high molar conversions were obtained with recombinant hydroperoxide lyase (50% for hexanal and 26% for hexenal formation), and no side products were formed. Furthermore, recombinant hydroperoxide lyase lacks isomerase activity, allowing production of (3Z)-hexenal, which could not be obtained in previously described processes. Recombinant hydroperoxide lyase is stable and can be stored at 4 degrees C for 1 month without significant loss of activity.  相似文献   

基于优先分配的玉米单个籽粒生长模拟     

陈尤佳  李双伟  Gerrit Hoogenboom  郭炎  李保国  马韫韬 《农业工程学报》2015,31(Z2):152-158

精确预测作物产量对于作物生产、栽培措施优化等具有重要意义。玉米单个籽粒的质量差异对玉米产量有显著影响,并且雌穗不同位置的籽粒获取同化物的能力不同。当前的玉米模型中由于缺乏基于单个籽粒生长机制的模拟过程,从而限制了其在更广泛环境下对产量的模拟精度和预测能力。为了量化雌穗不同位置籽粒对于同化物的竞争能力,基于源库理论建立了玉米单个籽粒灌浆过程的模型,并引入“优先权”方程量化雌穗一列籽粒中每个籽粒获取同化物的“优先”能力,整合进入潜在籽粒生长需求计算新的籽粒库强。通过多年多源库水平的玉米田间试验数据对模型的有效性进行系统评估。结果表明,引入“优先权”后明显提高不同位置籽粒的干质量的模拟精度。这为理解单个籽粒的生长发育过程、玉米产量形成过程提供基础依据。  相似文献   

A laboratory test protocol to evaluate effects of plant protection products on mortality and reproduction of the predatory mite<Emphasis Type="Italic">hypoaspis aculeifer</Emphasis> canestrini (acari: laelapidae) in standard soil     

Frank?M.?BakkerEmail author  Rik?Feije  André?J.?Grove  Gijs?Hoogendoorn  Gerrit?Jacobs  Edwin?D.?Loose  Pam?van?Stratum 《Journal of Soils and Sediments》2003,3(2):73-77

We provide a test protocol to evaluate the effects of plant protection products on mortality and reproductive performance ofHypoaspis aculeifer (Acari: Laelapidae). The test design is in compliance with standard characteristics of extended laboratory studies as formulated by international expert panels dealing with non-target arthropod testing schemes. Potential effects on survival rates are evaluated by assessing mortality after an exposure period of 14 days that starts with protonymphs. The reproductive performance of surviving mites is studied by following the egg production of individually isolated females over a 7-day period. The hatching success of these eggs is assessed subsequently. Using several years’ data obtained from water control treatments, we propose criteria to evaluate the validity of individual experiments.  相似文献   

Solute leaching in a sandy soil with a water-repellent surface layer: A simulation   总被引：5，自引：0，他引：5  

Gerrit H. de Rooij  Peter de Vries 《Geoderma》1996,70(2-4):253-263

Many sandy soils in the Netherlands have a water-repellent surface layer covering a wettable soil with a shallow groundwater table. Fingers form in the water-repellent surface layer and rapidly transport water and solutes to the wettable soil in which the streamlines diverge. Although several field observations are available, this system has not yet been studied systematically. In this paper, we present a model with a steady-state water flow to which solutes are added as a pulse. The model predicts the flow through the distribution zone and through the finger in the water-repellent surface layer with a closed form solution and transport in the wettable subsoil numerically. Model calculations show that the travel time through the water-repellent surface layer and the thickness and hydraulic conductivity of the wettable soil have the strongest effect on the arrival time of the solute pulse at groundwater level. The calculations also show that, assuming transport in the wettable subsoil to take place in fingers, the travel time is considerably shorter than when the diverging flow in the wettable soil is included.  相似文献