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1.
The effects of ferulic acid and catechin on starch pasting properties were studied as part of an investigation into the structure and functionality of phenolics in starch‐based products. Commercial maize starch, starches from sorghum cultivars (SV2, Chirimaugute, and DC‐75), and the phenolic compounds ferulic acid and catechin were used in the investigation. Pasting properties were measured using rapid viscosity analysis. Ferulic acid and catechin (up to 100 mg each) were added to maize or sorghum starch (3 g, 14% mb) in suspensions containing 10.32% dry solid content. Addition of catechin resulted in pink‐colored pastes, whereas ferulic acid had no effect on paste color. Ferulic acid and catechin decreased hot paste viscosity (HPV), final viscosity, and setback viscosity of maize and sorghum starch pastes, but had no influence on the peak viscosity (PV) of the former. Both phenolics increased breakdown viscosity. Ferulic acid had greater influence on HPV, final viscosity, breakdown, and setback than catechin. Addition of catechin under acidic conditions (pH 3) decreased HPV, final viscosity, and setback of maize starch, but alkaline conditions (pH 11) slightly increased setback. Both acidic and alkaline conditions resulted in increased breakdown. Investigations on model‐system interactions between ferulic acid or catechin and starch demonstrated that phenolic type and pH level both significantly influence starch pasting properties, with ferulic acid producing a more pronounced effect than catechin. The significance of these interactions is important, especially in food matrices where phenolics are to be added as functional food ingredients. 相似文献
2.
Effect of Oil Content and pH on the Physicochemical Properties of Corn Starch‐Soybean Oil Composites
Starch‐lipid composites are a new category of fat replacers. The physicochemical properties of reconstituted corn starch and soybean oil composites (CSSBOC) were evaluated and compared with the properties of reconstituted jet‐cooked corn starch (JCCS). Gel firmness, thermal properties, and hot pasting properties at two pH levels and two oil content levels were studied. Amylose content of CSSBOC was unaffected by processing. Buffer pH significantly affected the firmness of the gels made with JCCS. Gels appeared to have a more ordered structure and were firmer at pH 3.4 than at pH 6.0. The firmness of gels made with CSSBOC was not affected by pH or oil content. Retrogradation enthalpy of the gels made with JCCS was significantly affected by pH. Differences in the thermal characteristics of gels made with CSSBOC were attributed to pH and oil content. Peak viscosity, cold paste viscosity, and breakdown viscosity changed significantly when CSSBOC pastes were reconstituted in different pH buffers. Only hot paste viscosity and cold paste viscosity changed significantly when JCCS pastes were reconstituted in different pH buffers. Results establish critical parameters for processing decisions and for the understanding of the behavior of CSSBOC in food system models in which pH is an important factor. 相似文献
3.
Xu Z Zhong F Li Y Shoemaker CF Yokoyama WH Xia W 《Journal of agricultural and food chemistry》2012,60(2):658-664
Konjac glucomannan (KG, neutral), carboxymethylcellulose (CMC, negatively charged), and chitosan (positively charged) were added to cornstarch dispersions to study the effect of polysaccharide-starch interactions on starch gelatinization properties. Pasting and retrogradation properties were measured with a rheometer and DSC. Swelling properties of the starch granules were determined by solubility index, swelling power, and particle size distribution. Depending on the nature of the different polysaccharides, viscosities of cornstarch dispersions were affected differently. The particle size distributions were not influenced by the addition of any of the polysaccharides. Swelling results showed that the KG and CMC molecules interacted with the released or partly released amylose in the cornstarch dispersions. This was correlated with the short-term retrogradation of the starch pastes being retarded by the additions of KG and CMC. However, the chitosan molecules appeared not to associate with the amylose, so the retrogradation of the chitosan-cornstarch dispersions was not retarded. 相似文献
4.
酸性土壤上易产生铝（Al）毒害作用，缓解Al毒对于污染土壤上超积累植物的生长及重金属有效削减具有重要意义。本研究比较了不同措施对镉（Cd）超积累植物伴矿景天的Al胁迫缓解作用，结果发现：① 在水培条件下，锌添加可促进了Al胁迫下伴矿景天根表Cd2+吸收速率，而添加氯化钙或柠檬酸没有显著的缓解作用；② 在盆栽试验条件下，添加石灰处理显著提高了土壤pH，促进了伴矿景天生长和地上部对Cd的吸收，但添加生物质炭或柠檬酸没有显著缓解Al毒对伴矿景天生长和Cd吸收的抑制，添加柠檬酸反而加剧了土壤酸化，提高了土壤Al的活性；③在伴矿景天与荞麦间作条件下，其一定程度上降低了土壤的Al活性，在合适的种植密度下并未显著影响伴矿景天单株地上部Cd吸收量。综上，酸性土壤上耐Al作物与修复植物间作、结合添加改良剂调控Al毒，能够不显著降低土壤Cd的有效性和修复植物的Cd吸收，进而实现污染土壤的边生产边修复。 相似文献
5.
不同介质条件对银杏淀粉糊流变特性的影响 总被引：3，自引：0，他引：3
淀粉糊流变特性是影响淀粉类食品加工品质的主要因素。该文采用布拉班德尔黏度计，考察不同介质条件如浓度、pH值、蔗糖和食盐对银杏淀粉糊黏度特性的影响。银杏淀粉糊的布拉班德尔黏度测定结果表明：随着银杏淀粉糊浓度增加,其起糊温度降低，峰值黏度增高，热稳定性、冷稳定性下降，凝沉性增强；60 g/kg银杏淀粉糊黏度性质受酸碱介质的影响较大，在pH值中性7左右，其淀粉糊黏度热稳定性最好，凝沉性最强，但冷稳定性最差；食品介质蔗糖对60 g/kg银杏淀粉糊黏度曲线影响较大，其淀粉起糊温度、峰值黏度随蔗糖浓度增加而增加，淀粉糊黏度的冷稳定性、热稳定性均降低，凝沉性增强；而食盐影响较小。该结果对银杏淀粉类食品深加工开发具有较大的指导意义。 相似文献
6.
Waxy maize and potato starches were dispersed in pH 6.0 and 8.0 aqueous solutions (1%) of an ionic gum (sodium alginate, sodium carboxymethylcellulose, and xanthan). The mixture was dried at 45°C overnight and then heat‐treated 2 hr at 130°C. Effects on the paste viscosity of the products in a pH 7.0 buffer were examined. Heating with sodium alginate or sodium carboxymethylcellulose (CMC) increased the paste viscosity of waxy maize starch but reduced that of potato starch. In both starches, xanthan effected greater viscogram changes than did sodium alginate or CMC. Use of xanthan in the treatment produced products with restricted granular swelling and increased shear stability of the pastes. The pH of the starch‐gum mixtures affected the thermally induced viscosity changes. Mild acidity (pH 6.0) effected a viscosity decrease for the heat‐treated starch product, whereas alkalinity (pH 8.0) raised the viscosity regardless of the presence of gum. But pH 6 before heat treatment was favored for viscosity increase by sodium alginate, whereas pH 8 gave a greater increase in viscosity when xanthan was used. By using gum mixtures such as xanthan‐alginate and xanthan‐CMC, both viscosity increase and good shear‐stability were achieved. 相似文献
7.
有机酸在岩石矿物溶蚀风化及土壤形成的过程中具有较强的促进作用，了解柠檬酸对珊瑚砂的溶蚀过程对我国岛礁建设具有重要意义。本文通过不同浓度、不同pH柠檬酸溶液对珊瑚砂的溶蚀实验，研究柠檬酸对珊瑚砂的溶蚀过程，探讨其溶蚀机理。结果表明，在不同浓度柠檬酸溶液中，反应初期珊瑚砂中的Ca2+、Mg2+迅速溶出，随后大量的Ca2+与柠檬酸反应生成柠檬酸钙沉淀。平衡时溶液中Ca2+、Mg2+浓度随着柠檬酸浓度的增加而增加。在不同初始pH柠檬酸溶液中，当pH<7时，溶液中Ca2+、Mg2+的浓度随着初始pH的升高而降低，Ca2+、Mg2+主要由碳酸盐矿物与H+反应而溶出。当初始pH≥7时，Ca2+、Mg2+与柠檬酸生成络合物促进Ca2+、Mg2+的溶出，随着pH的升高，Ca2+、Mg2+浓度略有降低。珊瑚砂的溶蚀与柠檬酸钙的沉淀结晶主要受pH控制。通过XRD和SEM的分析表明，高浓度柠檬酸与珊瑚砂反应生成片状的柠檬酸钙沉淀，且饱和溶液中柠檬酸与钙离子的结晶生成平整规则的条状四水合柠檬酸钙沉淀。珊瑚砂溶蚀过程中镁方解石最先发生溶蚀，其次为文石，最后为方解石。 相似文献
8.
Calcium chloride, and to a lesser extent MgCl2, aided in the separation of membranes by centrifugation from cod (Gadus morhua) muscle homogenates solubilized at pH 3 in the presence of citric acid or malic acid but not lactic acid. Adding citric acid and Ca2+ before solubilizing the cod muscle homogenates was needed for the effect. At 1 mM citric acid, 70-80% of the phospholipid and 25-30% of the protein were removed at 10 mM Ca2+. At 8 mM Ca2+, citric acid showed an optimal effect on phospholipid removal at 5 mM with 90% of the phospholipid and 35% of the protein removed. The treatment with citric acid and Ca2+ was also effective in separating the membrane from solubilized herring (Clupea harengus) muscle homogenate. Ca2+ and citric acid might exert their influence by disconnecting linkages between membranes and cytoskeletal proteins. 相似文献
9.
Pasting, rheological, and water‐holding properties of buckwheat (Fagopyrum esculentum) flour obtained from whole achenes separated into three particle sizes, and three commercial flours (Fancy, Supreme, and Farinetta) were measured with or without jet‐cooking. Fancy had instantaneous paste viscosity (measured using RVA) after jet‐cooking that was not observed for Supreme or Farinetta, and paste viscosity was lower for the latter two flours. Supreme jet‐cooked flour exhibited higher peak viscosity than flour without jet‐cooking, and paste exhibited high shear‐thinning. Fancy exhibited strongest viscoelastic properties (measured using a rheometer). Jet‐cooking damaged buckwheat flour structure, thereby reducing viscoelasticity. Buckwheat flour pastes experienced shear‐thinning over a wide range of shear rates. Jet‐cooking greatly enhanced water‐holding capacity. Buckwheat flour particle size did not greatly influence paste viscosity. Study showed buckwheat flours have unique pasting and rheological characteristics that have different food applications, which could especially be useful for people with celiac disease as buckwheat is gluten‐free. 相似文献
10.
甘草根瘤菌CCNWGX035的抗逆特性及结瘤特征研究 总被引：1，自引：0，他引：1
Thirty-nine rhizobial isolates were isolated from the root nodules of Glycyrrhiza uralensis and Glyeyrrhiza glabra, growing in the arid and semiarid regions of northwestern China, to test their taxonomic position and stress tolerance and to select one promising putative inoeulant strain for further studies. On the basis of 113 physiological and biochemical characteristics, the isolates were clustered into three groups. One isolate CCNWGX035 was found to have high tolerance to NaC1, pH, and temperature. By sequencing the 16S rDNA, isolate CCNWGX035 was placed in genus Mesorhizobium. Nodulation tests demonstrated that the isolate not only formed nitrogen-fixing nodules on its original host plant Glyeyrrhiza glabra, but also on Sophora vieiifolia, Lotus cornieulatus, Trifolium repens, Melilotus suaveolens, and Sophora alopecuroides. On the basis of sequence analysis of the nodA gene, isolate CCNWGX035 was closely related to strains of the genus Mesorhizobium, exhibiting some novel characteristics of root nodule bacteria. 相似文献
11.
12.
单一及复合有机酸对土壤中镉形态的影响研究 总被引：5，自引：0，他引：5
为寻找可行的强化重金属污染土壤植物修复的方法,研究了柠檬酸与复合有机酸(苹果酸+柠檬酸)对土壤中重金属Cd各形态的影响。结果表明,对于不同污染程度的CdⅠ~CdⅣ土壤,单一与复合添加有机酸均能有效活化土壤中重金属Cd;当复合添加2.5 mmol kg-1苹果酸+7.5 mmol kg-1柠檬酸时土壤中最具活性的可交换态Cd百分含量增长率显著高于单一添加10 mmol kg-1柠檬酸时的增长率。 相似文献
13.
低分子量有机酸对高岭石中铝释放的影响 总被引：22，自引：3，他引：22
选择了几种土壤中可能存在的低分子量脂肪羧酸 ,研究了它们对高岭石中铝释放的影响。结果表明 ,有机酸可以通过络合作用促进高岭石中铝的释放。几种有机酸对体系中可溶性铝影响的大小顺序为 :草酸 >柠檬酸 >丙二酸 >苹果酸 >乳酸。草酸、柠檬酸和乳酸对可溶性铝释放的促进作用随体系pH的升高而减小 ,其中草酸体系中可溶性铝随pH的变化幅度最大。在苹果酸体系中 ,可溶性铝随pH的升高而稍有增加。体系中的可溶性铝随有机酸浓度的增加而增加 ,而交换性铝随柠檬酸浓度的增加而减少 ,先随苹果酸浓度增加而增加 ,然后又逐渐减少。与对照相比 ,柠檬酸和草酸使交换性铝的量减小 ,苹果酸和乳酸在低pH下使交换性铝明显增加 ,而苹果酸在较高pH下使交换性铝减少。有机酸影响释放出的铝在固液相间的分配比 ,苹果酸在低pH下使体系中释放出的大部分铝以交换性形态存在 ,而在较高pH下 ,大部分铝以可溶形态存在。在草酸体系中 ,释放出铝的大部分都以可溶形态存在。不同有机酸的不同表现与体系中铝的溶解平衡、铝的吸附 -解吸平衡、有机酸的吸附 -解吸平衡、有机酸的离解平衡和铝与有机酸的络合 -离解平衡有关。 相似文献
14.
Ornanong S. Kittipongpatana Waree Chaitep Nisit Kittipongpatana Reinhard Laenger Klanarong Sriroth 《Cereal Chemistry》2007,84(4):331-336
Carboxymethyl rice starches (CMRS) were prepared from nine strains of native rice starches with amylose contents of 14.7–29.1%. The reaction was conducted at 50°C for 120 min using monochloroacetic acid as a reagent under alkaline conditions and 1-propanol as a solvent. After determining the degree of substitution (DS), the physicochemical properties including water solubility, pH, and viscosity of 1% (w/v) solution, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses of the granules, as well as some pharmaceutical properties of CMRS powders and pastes were investigated. The DS range was 0.25–0.40. All CMRS dissolved in unheated water and formed viscous gel. A good positive correlation was observed between amylose content and DS (r = 0.9278) but not viscosity. SEM and XRD concurrently revealed significant physical alteration of CMRS granules compared with those of native starches, which reflected the changes in the properties of CMRS. At 3% (w/w), CMRS can function as tablet binder in the wet granulation of both water-soluble and water-insoluble diluents. The tablets compressed from these granules showed good hardness with fewer capping problems compared with those prepared using the pregelatinized native rice starch as a binder. In addition, most CMRS pastes formed clear films with varying film characteristics, depending upon the amylose content of the native starches. This type of modified rice starch can potentially be employed as a tablet binder and film-former for pharmaceutical dosage formulations. 相似文献
15.
采用批量培养和平衡吸附法,选取原土及微团聚体颗粒组为对象,研究Zn(II)、Cd(II)单一存在、二元竞争及竞争体系中加入柠檬酸(0.1,1,10mmol/L)等3种处理的等温吸附特性及影响。结果表明:(1)以专性吸附方式为主的多层吸附随Zn~(2+)、Cd~(2+)强度增加逐渐饱和,吸附能力以0.002mm最优、0.05~0.002mm和原土次之,0.25~0.05mm和2~0.25mm结合能力稍差,不同条件下Cd较Zn更易积累。吸附过程为自发吸热反应,热力学Freundlich方程(Zn:R2=0.960~0.997;Cd:R2=0.957~0.995)拟合结果优于Langmiur方程(Zn:R2=0.952~0.995;Cd:R2=0.913~0.991)。最大吸附量与有机质含量具有显著相关性。(2)单一处理Zn、Cd的固持效果明显、共存处理时Zn、Cd竞争行为表现为彼此削弱,Zn对Cd的吸附具有更强抑制作用。(3)添加不同浓度柠檬酸后Zn、Cd吸附水平介于单一及共存处理之间呈动态变化(Zn、Cd接近),0.1~1mmol/L利于Zn、Cd固持,增至10mmol/L后加速淋洗,仅0.002mm粒径富集量持续提升。表明柠檬酸作为一种调节剂,能适度保持土壤Zn供给并弱化Cd迁移活性,缓解茶园土壤复合污染。 相似文献
16.
This study was conducted to investigate the kinetics of Hg adsorption by noncrystalline Al hydroxide as influenced by various pH conditions and cysteine (cys), glycine (gly), and citric acid (cit), which have different structures and functionalities, as low-molecular-weight organic ligands using the GEOCHEM-PC software. The influence of these organic ligands on the kinetics of Hg adsorption varied according to their concentration, structure, and functionality and pH. The adsorption of Hg followed multiple first order kinetics with initial rapid adsorption, followed by slow adsorption. Cysteine suppressed or enhanced Hg adsorption, depending on pH and its concentration. Glycine and citric acid exerted suppressing and enhancing effects, respectively, with the exception of at pH 4.5 and at lower concentrations, at which no influence was observed as compared to the control. Two mechanisms were thought to mediate the adsorption of Hg(II); specific surface complexation in the control, cysteine and glycine systems, and ligand exchange in the citric acid system. The Hg adsorption at all levels of organic ligands decreased with increasing pH, with the exception of at the higher concentration of cysteine, at which the reverse trend was observed. The influence of organic ligands on the dynamics of Hg in the freshwater environment merits further study. 相似文献
17.
低分子量有机酸强化烟草修复镉污染土壤的适用性研究 总被引：6，自引：1，他引：5
采用盆栽试验,以0.125mmol/kg EDTA为对照,研究3种低分子量有机酸(酒石酸、柠檬酸和草酸)在强化烟草修复镉污染土壤中应用的可行性。3种低分子量有机酸(LMWOA)均可显著降低土壤pH,提高镉的有效含量,酒石酸和草酸对镉在烟草中转运有抑制作用,柠檬酸在酸性土壤中促进镉在烟草中转运,在中性土壤中则起抑制作用。31.25mmol/kg LMWOA对烟草地上部的生长有一定的促进作用,该浓度的柠檬酸和草酸使酸性土壤中烟草地上部镉累积量分别提高42.95%和28.67%,柠檬酸还使中性土壤中烟草地上部镉的累积量提高40.91%,所有酒石酸处理镉在烟草地上部的累积量均降低,EDTA使酸性土壤中烟草地上部镉的累积量提高24.56%,对中性土壤中烟草地上部镉累积量的影响不显著。表明柠檬酸和草酸具有强化烟草地上部对镉的吸收、提高烟草提取土壤镉效率的作用,但要获得与EDTA相当的效果,需大大提高其用量,这必然导致修复成本大大提高,故不宜用于强化烟草修复镉污染土壤。 相似文献
18.
采用室内模拟试验研究了低分子量有机酸(柠檬酸、草酸、苹果酸、酒石酸)对红壤磷酸单酯酶活性的影响。结果表明,低浓度有机酸(<1μmol g-1)对磷酸单酯酶活性有促进作用,且促进作用大小依次为柠檬酸≈草酸>苹果酸>酒石酸;而高浓度有机酸(>5μmol g-1)则为抑制作用,且抑制作用大小依次为柠檬酸>草酸>苹果酸>酒石酸。当体系pH趋向酶促反应最佳pH时,磷酸单酯酶活性增强;反之,当体系pH远离酶促反应最佳pH时,磷酸单酯酶活性减弱。有机酸根一方面通过羧基的辅助作用提高磷酸单酯酶活性;另一方面通过释放土壤A l3+、Fe3+等金属离子,对土壤磷酸单酯酶活性有一定的抑制作用。 相似文献
19.
低分子有机酸/盐对森林暗棕壤铁的释放效应 总被引：1，自引：0，他引：1
模拟森林凋落物淋洗液中草酸/草酸盐和柠檬酸/柠檬酸盐的浓度范围,设计了不同浓度草酸/草酸盐和柠檬酸/柠檬酸盐溶液一次性浸提和多次连续浸提等系列实验,结果表明,草酸/草酸盐和柠檬酸/柠檬酸盐对暗棕壤铁具有活化作用,活化作用大小因有机酸/盐种类、浓度和土壤性质而异。随着低分子有机酸/盐浓度的增加,A1层和B层暗棕壤活化释放的铁也逐渐增多。pH 5.16的低分子有机盐溶液对A1层和B层暗棕壤铁的活化作用强于同浓度的相应低分子有机酸,即柠檬酸盐>柠檬酸,草酸盐>草酸,因此推断草酸盐和柠檬酸盐溶液促进暗棕壤铁活化释放的机理主要在于低分子有机酸阴离子的配位反应。柠檬酸/柠檬酸盐对A1层和B层暗棕壤铁的活化作用强于同浓度的草酸/草酸盐,即柠檬酸>草酸,柠檬酸盐>草酸盐,这主要与柠檬酸对铁较强的络合能力及较大的离解常数有关。A1层与B层相比,草酸/草酸盐和柠檬酸/柠檬酸盐均对B层暗棕壤释放的铁量较高。另外,低分子有机酸对暗棕壤铁的释放并不是一次就能完成的,第一次以后的连续4次浸提仍源源不断释放出数量可观的铁。 相似文献
20.
不同pH下有机酸对针铁矿和膨润土吸附Cd2+、Pb2+的影响 总被引：1，自引：0，他引：1
用平衡吸附法研究了不同pH下,三种有机酸(乙酸、酒石酸和柠檬酸)对针铁矿和膨润土等温吸附Cd2 、Pb2 的影响。结果表明:在加入的Cd2 、Pb2 浓度分别小于0.2 mmol L-1和4.0 mmol L-1时,针铁矿和膨润土吸附平衡体系的pH随加入重金属浓度的增加而降低,膨润土体系的pH降低更明显。在有机酸作用下,pH对针铁矿和膨润土吸附Cd2 、Pb2 的影响差异显著。3酒石酸>乙酸,其对膨润土吸附的影响差异不明显。 相似文献