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1.
Food Chem ; 336: 127716, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32768910

RESUMO

Jackfruit seed starch (JFSS) was modified by an improved extrusion cooking technology (IECT), and the supramolecular structure, molecular weight, debranched chain length distributions, relative crystallinity (Rc), and amylose content, were studied. During IECT, the α-1.4-glycosidic bond in amylopectin was broken, which led to decreased radius of gyration (Rg), number-average molar mass (Mn), weight-average molar mass (Mw), long chains and Rc. The medium and short chains and PI (Mw/Mn) increased, while the amylose content hardly changed. The crystalline structure of JFSS was converted from A-type to V-type. Increasing the temperature and screw speed during the treatment significantly increased the medium and short chains and Rg, while it decreased the long chains, amylose, Mn, Mw, PI, and Rc. However, the opposite effect was observed when increasing the moisture content. The in vitro digestibility of JFSS was significantly improved after IECT, due to destruction of starch supramolecular structure according to principal component analysis.


Assuntos
Artocarpus/química , Sementes/química , Amido/química , Amilopectina/química , Amilose/análise , Amilose/química , Culinária/métodos , Digestão , Peso Molecular , Análise de Componente Principal , Temperatura
2.
Food Chem ; 336: 127711, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32777656

RESUMO

Wrinkled and round peas (two varieties each type) cultivated in two locations were milled to obtain fine and coarse wrinkled (WPF) and round pea flour (RPF). WPF exhibited markedly increased pasting viscosities at 120 and 140 °C compared with 95 °C. Overall, the pasting properties of WPF were considerably lower than those of RPF. Resistant starch (RS) contents of cooked WPF (17.2-22.2%, dsb) were significantly larger than those of RPF (7.9-11.4%), resulting from higher starch gelatinization temperatures, greater amylose contents, and presence of more protein and fiber in WPF. The two particle sizes affected the water-holding capacity (WHC) of WPF, gelatinization enthalpy changes (ΔH) of WPF and RPF, and pasting properties and starch digestibility of RPF. Pearson correlation and principal component analysis (PCA) were conducted to reveal the relationships among the techno-functional parameters of pea flours. Wrinkled pea showed promise to generate new pea flours with distinct functionality and enhanced nutritional value.


Assuntos
Farinha , Ervilhas/química , Amilose/química , Fibras na Dieta/metabolismo , Digestão , Farinha/análise , Valor Nutritivo , Tamanho da Partícula , Proteínas de Vegetais Comestíveis/análise , Amido/química , Amido/farmacocinética , Temperatura , Viscosidade
3.
J Chromatogr A ; 1625: 461303, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709346

RESUMO

The chromatographic performances of four coated and immobilized amylose phenylcarbamate-based chiral columns were evaluated and compared under normal phase (NP) elution conditions by using chiral 4,4'-bipyridine derivatives as analytes. n-Hexane/2-propanol 90:10 and n-hexane/2-propanol/methanol 90:5:5 mixtures were employed as mobile phases (MPs), and the effect of adding methanol in the MP on retention and selectivity was considered. The effect of temperature on retention and selectivity was also evaluated, and overall thermodynamic parameters associated with the analyte adsorption onto the CSP surface were derived from van't Hoff plots. Interesting cases of enantiomer elution order (EEO) reversal, which are dependent on the nature of polar modifier, analyte structure, column-type, and temperature, were observed. The impact of substitution pattern and electronic properties of analytes and selectors on the separation behaviour was investigated by correlating chromatographic parameters and molecular properties determined by using density functional theory (DFT) calculations. Both coated and immobilized amylose tris(3,5-dimethylphenylcarbamate) columns allowed for the baseline enantioseparation (2.0 ≤ RS ≤ 4.9) of all 4,4'-bipyridines considered in this study. These results appear particularly useful because both enantiomers of these 4,4'-bipyridine derivatives are currently under investigation as new inhibitors of transthyretin fibrillogenesis, a biochemical phenomenon which is implicated to cause amyloid diseases.


Assuntos
Amilose/química , Piridinas/química , 2-Propanol/química , Adsorção , Hexanos/química , Metanol/química , Modelos Moleculares , Fenilcarbamatos/química , Eletricidade Estática , Estereoisomerismo , Temperatura
4.
J Chromatogr A ; 1625: 461280, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709331

RESUMO

Polysaccharide-based chiral stationary phases (CSPs) are outstandingly suitable to play a key role in chiral HPLC method selection strategies, since they provide high success rates. One reason for this ability is that they adopt a diversity of higher order structures in various eluents, resulting in versatile chiral environments. A potential to extend this versatility further was expected and examined in the present study, based on the recently discovered hysteretic behavior of a widely used chiral selector (CS), amylose tris(3,5-dimethylphenylcarbamate). The hindered transitions of its structure, which are behind the history dependence of its separation ability, were used as a tool to identify distinct states of the chiral selector in order to exploit an extended selectivity space. The identification was carried out using a single diagnostic compound, as opposed to the common approach where testing a library of compounds is required. Eluent mixtures consisting of 2-propanol and either methanol or ethanol were scrutinized in terms of stability and robustness of the observed retentions. The solvent mixtures that were eligible for practical application in these respects were used to construct a screening sequence, including identical compositions combined with different column pretreatment. The gain achievable by using the proposed sequence was then evaluated using 15 enantiomer pairs with focus on resolution, enantiomer elution order and chemoselectivity.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Compostos Orgânicos/química , 2-Propanol/química , Amilose/análogos & derivados , Amilose/química , Etanol/química , Indanos/química , Metanol/química , Oxidiazóis/química , Fenilcarbamatos/química , Solventes/química , Estereoisomerismo , Estilbenos/química
5.
J Chromatogr A ; 1625: 461281, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709332

RESUMO

Polysaccharide-based chiral stationary phases (CSPs) are the most used chiral selectors in HPLC. These CSPs can be used in normal, polar organic and aqueous-organic mobile phases. However, normal and polar organic mobile phases are not adequate for chiral separation of polar compounds, for the analysis of aqueous samples and for MS detection. In these situations, reversed phase conditions, without the usual non-volatile additives incompatible with MS detection, are preferable. Moreover, in most of the reported chiral chromatographic methods, retention is too large for routine work. In this paper, the chiral separation of 53 structurally unrelated compounds is studied using three commercial amylose-based CSPs -coated amylose tris(3,5-dimethylphenylcarbamate) (Am1), coated amylose tris(5-chloro-2-methylphenylcarbamate) (Am2), and immobilised amylose tris(3-chloro-5-methylphenylcarbamate) (Am3)-. Chiral separations are carried out using acetonitrile/ammonium bicarbonate (pH = 8.0) mixtures, reversed mobile phases compatible with MS detection. To provide realistic conditions for routine analysis, maximum retention factors are set to 15. Retention and enantioresolution behaviour of compounds in those CSPs are compared. On the other hand, to compare and describe the resolution ability of these CSPs, 58 structural variables of the compounds are tested to model for the first time a categorical enantioresolution (CRs) for Am1 and Am3 CSPs. Discriminant partial least squares, for one response categorical variable (DPLS1) is used for feature selection, modelling. The final DPLS1 models showed good descriptive ability.


Assuntos
Amilose/química , Cromatografia de Fase Reversa/métodos , Espectrometria de Massas/métodos , Modelos Químicos , Cromatografia Líquida de Alta Pressão , Análise dos Mínimos Quadrados , Análise de Regressão , Estereoisomerismo
6.
J Chromatogr A ; 1624: 461218, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540066

RESUMO

In this study, amylose- and cellulose-phenylcarbamate-based chiral columns with different chiral-selector (CS) chemistries were compared to each other for the separation of enantiomers of basic chiral analytes in acetonitrile and aqueous-acetonitrile mobile phases in HPLC. For two chemistries the amylose-based columns with coated and immobilized CSs were also compared. The comparison of CSs containing only electron-donating or electron-withdrawing substituents with those containing both electron-donating and electron-withdrawing substituents showed opposite results for the studied set of chiral analytes in the case of amylose and cellulose derivatives. Along with the chemistry of CS the focus was on the behavior of polysaccharide phenylcarbamates in acetonitrile versus aqueous acetonitrile as eluents. In agreement with earlier results, it was found that in contrast to the commonly accepted view, polysaccharide phenylcarbamates do not behave as typical reversed-phase materials for basic analytes either. In the range of water content in the mobile phase of up to 20-30% v/v the behavior of these CSs is similar to hydrophilic interaction liquid chromatography (HILIC)-type adsorbents. This means that with increasing water content in the mobile phase up to 20-30% v/v, the retention of analytes mostly decreases. The important finding of this study is that the separation efficiency improves for most analytes when switching from pure acetonitrile to aqueous acetonitrile. Therefore, in spite of reduced retention, the separation of enantiomers improves and thus, the HILIC-range of mobile phase composition, offering shorter analysis time and better peak resolution, is advantageous over pure polar-organic solvent mode. Interesting examples of enantiomer elution order (EEO) reversal were observed for some analytes based on the content of water in the mobile phase on Lux Cellulose-1 and Lux Amylose-2 columns.


Assuntos
Amilose/química , Celulose/química , Cromatografia Líquida de Alta Pressão/métodos , Preparações Farmacêuticas/isolamento & purificação , Fenilcarbamatos/química , Acetonitrilos/química , Elétrons , Etanolaminas/análise , Etanolaminas/isolamento & purificação , Preparações Farmacêuticas/análise , Propanolaminas/análise , Propanolaminas/isolamento & purificação , Propranolol/análise , Propranolol/isolamento & purificação , Estereoisomerismo , Água/química
7.
J Chromatogr A ; 1624: 461240, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540078

RESUMO

In this work, the use of different solvents and temperatures was explored, aiming to evaluate their influence on the enantioseparation of pesticides by HPLC in polar-organic conditions, employing a column containing immobilized amylose tris(3-chloro-5-methylphenyl-carbamate). The chiral separation of seventeen different pesticides widely used as herbicides, fungicides, insecticides and precursors were studied. The mobile phases included methanol, ethanol, iso-propanol, n-propanol and acetonitrile; either pure or containing additives such as diethylamine, trifluoroacetic acid, formic acid, acetic acid or mixtures thereof. We studied the influence of these eluents on chiral separation of those pesticides in terms of retention factor, enantioselectivity, enantioresolution and peak symmetry. Regarding temperature influence, evaluated within the range 5 - 40 °C, nearly all the compounds decreased their retention and selectivity factors with the increase in temperature, although the effect was dependent on the mobile phase solvent. Moreover, estimation of thermodynamic parameters was performed based on linear van´t Hoff plots.


Assuntos
Amilose/análogos & derivados , Compostos Orgânicos/química , Praguicidas/química , Praguicidas/isolamento & purificação , Fenilcarbamatos/química , Temperatura , Amilose/química , Cromatografia Líquida de Alta Pressão , Padrões de Referência , Solventes/química , Estereoisomerismo
8.
Food Chem ; 330: 127328, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32569940

RESUMO

Granular protein is an important structural feature in determining starch digestibility. High-amylose wheat starch (HAWS) with >80% amylose content contains more granular protein than wild-type starch. As analyzed by mass spectrometry-based proteomics, granular-bound starch synthase (GBSS) is the major granular protein in isolated starch materials. GBSS content increases with amylose content (Spearman's correlation, p < 0.05), whereas the abundance relative to other proteins is similar among starches. Multiple amylase inhibitors were also identified. From Michaelis-Menten analysis, HAWS has a similar Km (Michaelis constant) as wild type, suggesting initial enzymatic binding is similar. After the pre-digestion of proteins, wild type had a greater change in starch digestibility than HAWS, probably due to the latter having 'thicker' granular-protein layers and higher enzymatic resistance of substrate per se. Overall, the study suggests that the greater granular protein content in HAWS is a factor that contributes to slower amylolysis compared to wild type.


Assuntos
Amilose/metabolismo , Proteínas de Plantas/metabolismo , Sintase do Amido/metabolismo , Amido/química , Triticum/química , Amilose/análise , Amilose/química , Digestão , Hidrólise , Cinética , Proteínas de Plantas/análise , Amido/metabolismo , Sintase do Amido/análise , Espectrometria de Massas em Tandem , Triticum/metabolismo , alfa-Amilases/química , alfa-Amilases/metabolismo
9.
J Chromatogr A ; 1623: 461213, 2020 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-32505297

RESUMO

In the present study separation of enantiomers of some chiral neutral, basic and weakly acidic analytes was investigated on the chiral stationary phase (CSP) made by covalent immobilization of amylose tris(3-chloro-5-methylphenylcarbamate) onto aminopropylsilanized (APS) silica in nano-liquid chromatography (nano-LC) in aqueous methanol or acetonitrile mixtures. It has been shown that similar to high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) this chiral selector is useful for separation of enantiomers of neutral, basic and acidic analytes also in nano-LC. In comparison to our previous research, in which the chiral selector (CS) was bonded on native silica, in this study, the CS was immobilized on APS silica in order to improve chromatographic performance towards basic analytes. In fact, some improvement was observed and surprisingly not only for basic but also for neutral and acidic analytes. Again, quite unexpectedly almost no electroosmotic flow (EOF) was observed in capillaries packed with ca. 20% (w/w) amylose tris(3-chloro-5-methylphenylcarbamate) immobilized onto APS silica although the same APS silica before attachment of chiral selector exhibited significant EOF. In order to generate EOF in the capillaries with the CSP and enable capillary electrochromatographic (CEC) experiment on it, the short segment of the capillary column was packed with APS silica without chiral selector. The EOF in such capillary enabled CEC experiment and some preliminary results are reported here.


Assuntos
Amilose/análogos & derivados , Eletrocromatografia Capilar/métodos , Cromatografia Líquida/métodos , Fenilcarbamatos/química , Dióxido de Silício/química , Ácidos/química , Amilose/química , Flavanonas/análise , Estereoisomerismo
10.
Food Chem ; 324: 126858, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32353656

RESUMO

Wheat flour noodles are sometimes fortified with ß-glucan for nutritional value, but this can decrease eating quality. The contributions of ß-glucan and starch molecular fine structure to physicochemical properties of wholemeal oat flour and to the texture of oat-fortified white salted noodles were investigated here. Hardness of oat-fortified noodles was controlled by the longer amylopectin chains (DP ≥ 26) and amount of longer amylose chains (DP ≥ 1000). Higher levels of ß-glucan, in the range from 3.1 to 5.2%, result in increased noodle hardness. Pasting viscosities of wholemeal oat flour positively correlate with the hardness of oat-fortified noodles. The swelling power of oat flour is not correlated with either pasting viscosities of oat flour or noodle hardness. Longer amylopectin chains and the amount of longer amylose chains both control the pasting viscosities of oat flour, which in turn affect noodle texture. This provides new means, based on starch and ß-glucan molecular structure, to choose oats with optimal starch structure and ß-glucan content for targeted oat-fortified noodle quality.


Assuntos
Avena/metabolismo , Amido/química , Triticum/metabolismo , beta-Glucanas/química , Amilopectina/química , Amilose/química , Farinha/análise , Dureza , Viscosidade
11.
Food Chem ; 327: 127047, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32454269

RESUMO

For more effective using of HHP (high hydrostatic pressure) in starch processing, in this study, molecular dynamics simulation was used to explore the effects of pressure on amylose molecular conformation at the atomic level. The results shown that, firstly, high pressure decreased the intramolecular hydrogen bonds and increased the amylose-solvent hydrogen bonds, which is consistent with the process of high pressure starch gelatinization. Secondly, high pressure made amylose polymers more "stout". Meanwhile, high pressure decreased the angle of α-1,4 glycosidic linkage and increased the dihedral angles of α-1,4 glycosidic linkage, which indicates that pressure has obvious effects on amylose molecular conformation. Thirdly, high pressure made amylose polymers more stable. Moreover, in view of the results of energies, HHP may have an opposite gelatinization mechanism to heating. The results may be complementary to the existing experimental phenomena and provide theoretical guidance value for the using of HHP in starch processing.


Assuntos
Amilose/química , Simulação de Dinâmica Molecular , Ligação de Hidrogênio , Pressão Hidrostática , Conformação Molecular , Solventes/química
12.
J Chromatogr A ; 1621: 461053, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32276857

RESUMO

The chromatographic properties of a new coated amylose tris(3-chloro-5-methylphenylcarbamate) were evaluated in supercritical fluid chromatography for the separation of enantiomers of chiral 1-aryl-5-aryl-pyrrolidin-2-one derivatives, potential anticancer agents, and some commercial drugs. The mobile phase consisted of CO2-modifier mixtures with 30% of either methanol or ethanol, the flow rate was 3 mL/min. The column oven temperature was 40 °C and the outlet pressure was 15 MPa, in order to limit the compressibility of the CO2, thus limiting density variation along the column. The obtained results were then compared to those observed toward 3 other stationary phases: the coated amylose tris(3,5-dimethylphenylcarbamate), the immobilized amylose tris(3,5-dimethylphenylcarbamate) and the coated amylose tris(5-chloro-2-methylphenylcarbamate). It was shown that the new coated amylose tris(3-chloro-5-methylphenylcarbamate) was the most retentive column whatever the studied compounds, particularly for thalidomide and omeprazole with retention factors up to 73.3 and 29.5for the second enantiomer, respectively. Concerning the enantioselectivity, even most of the compounds are separated on all the four columns, the coated amylose tris(3-chloro-5-methylphenylcarbamate) allows the best resolution for most of the ten studied analytes (except omeprazole for which the resolution values are equal to 7.8 and 9.7 on the coated amylose tris(3-chloro-5-methylphenylcarbamate) and amylose tris(3,5-dimethylphenylcarbamate), respectively). Acting in complementary ways, the two chlorinated stationary phases permitted the complete separation of enantiomers of nine compounds out of the ten.


Assuntos
Amilose/análogos & derivados , Cromatografia com Fluido Supercrítico/métodos , Amilose/química , Antineoplásicos/análise , Antineoplásicos/isolamento & purificação , Carbamatos/química , Preparações Farmacêuticas/análise , Preparações Farmacêuticas/isolamento & purificação , Fenilcarbamatos/química , Pirrolidinonas/análise , Pirrolidinonas/isolamento & purificação , Dióxido de Silício/química , Estereoisomerismo
13.
Food Chem ; 318: 126489, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32135425

RESUMO

In the present study, starches isolated from heat-moisture treated (HMT) adlay seeds were characterized with hierarchical structures and digestibility to understand the relationships in structural and digestible behaviors of starches in a HMT starch-based food system. The results indicated that HMT not only caused the disorganizations of hierarchical structures, but also promoted the molecular rearrangements and reassembly of starch chains to form a new ordered molecular aggregation architecture (i.e., highly ordered molecular structure, amylose-lipids complexes and thicker crystalline lamella). And the reinforced molecular interactions between starch molecules during HMT occurred to form more densely ordered structure, thus reducing the digestibility and digestion rate coefficients (k) of adlay starch. Particularly, HMT applied directly in adlay seeds with 30% moisture content displayed the highest resistant starch level (20.6%) and lowest k (2.74 × 10-3 min-1). Thus, the results are useful to realize the desired regulation of starch digestibility in adlay products following HMT.


Assuntos
Amilose/química , Coix/química , Lipídeos/química , Estrutura Molecular , Amido/química , Digestão , Temperatura Alta , Microscopia Eletrônica de Varredura , Sementes/química , Amido/ultraestrutura , Água/química
14.
Food Chem ; 318: 126490, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32146307

RESUMO

This study examined the contribution of amylose to the organization of each starch fraction in recrystallized starch. Amylosucrase (AS)-modified waxy potato starches with different branch chain lengths were completely solubilized with amylose (3:1 ratio) and recrystallized at 4 °C for 48 h. The content of rapidly digestible starch and resistant starch (RS) showed linear change with degree of AS modification, while slowly digestible starch (SDS) did not. The changes in structural characteristics were tracked according to serial removal of each fraction. Results from iodine binding property, branch chain length, X-ray diffraction, and thermal property analysis indicated that branch chain length of amylopectin determined the length of the amylose-amylopectin double helix and the mobility of amylose and that formation of SDS or RS could be induced by controlling the length of amylopectin chains. These findings could be used for production of customized starches with specific digestive properties for health benefits.


Assuntos
Amilopectina/química , Amilose/química , Glucosiltransferases/química , Solanum tuberosum/química , Amido/química , Cristalização , Digestão , Estrutura Molecular , Difração de Raios X
15.
Food Chem ; 318: 126477, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32126465

RESUMO

Water-extractable arabinoxylan (WEAX) could effectively improve the cereal food quality, while its regulatory effect on wheat starch properties has yet to be well-understood. This study selected the WEAX with different molecular weight (Mw) but same branched degree, and comparatively investigated their effects on the gelatinization and retrogradation behavior of wheat starch. The decreased degree of swelling power, solubility and peak viscosity suggested that low Mw WEAX (L-WEAX) could hinder starch gelatinization more evidently compared with high Mw WEAX (H-WEAX), due to the pronounced inhibition effect on amylose leaching and amylose-lipid complex formation. L-WEAX suppressed the recrystallization of amylose and thus the short-term retrogradation. However, H-WEAX mainly retarded the recrystallization of amylopectin, exerting a more significant inhibition effect on the long-term retrogradation. This study could provide a theoretical basis for enhancing the quality and extending the shelf life of starchy foods by selecting the optimum structure of WEAX.


Assuntos
Amido/química , Triticum/química , Xilanos/isolamento & purificação , Amilopectina/química , Amilose/química , Varredura Diferencial de Calorimetria , Cristalização , Gelatina/química , Microscopia Confocal , Peso Molecular , Viscosidade , Água/química , Difração de Raios X , Xilanos/química , alfa-Amilases/química , alfa-Amilases/metabolismo
16.
J Chromatogr A ; 1621: 461054, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32204880

RESUMO

The enantioselective separation of newly prepared, pharmacologically significant isopulegol-based ß-amino lactones and ß-amino amides has been studied by carrying out high-performance liquid chromatography on diverse amylose and cellulose tris-(phenylcarbamate)-based chiral stationary phases (CSPs) in n-hexane/alcohol/diethylamine or n-heptane/alcohol/ diethylamine mobile phase systems. For the elucidation of mechanistic details of the chiral recognition, seven polysaccharide-based CSPs were employed under normal-phase conditions. The effect of the nature of selector backbone (amylose or cellulose) and the position of substituents of the tris-(phenylcarbamate) moiety was evaluated. Due to the complex structure and solvation state of polysaccharide-based selectors and the resulting enantioselective interaction sites, the chromatographic conditions (e.g., the nature and content of alcohol modifier) were found to exert a strong influence on the chiral recognition process, resulting in a particular elution order of the resolved enantiomers. Since no prediction can be made for the observed enantiomeric resolution, special attention has been paid to the identification of the elution sequences. The comparison between the effectiveness of covalently immobilized and coated polysaccharide phases allows the conclusion that, in several cases, the application of coated phases can be more advantageous. However, in general, the immobilized phases may be preferred due to their increased robustness. Thermodynamic parameters derived from the temperature-dependence of the selectivity revealed enthalpically-driven separations in most cases, but unusual temperature behavior was also observed.


Assuntos
Amilose/análogos & derivados , Celulose/análogos & derivados , Cromatografia Líquida de Alta Pressão/métodos , Monoterpenos Cicloexânicos/química , Amidas/química , Amidas/isolamento & purificação , Amilose/química , Celulose/química , Lactonas/química , Lactonas/isolamento & purificação , Fenilcarbamatos , Estereoisomerismo , Temperatura , Termodinâmica
17.
Food Chem ; 320: 126609, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32222658

RESUMO

Bread crumb firming is largely determined by the properties of gluten and starch, and the transformations they undergo during bread making and storage. Amylose (AM) and amylopectin (AP) functionality in fresh and stored bread was investigated with NMR relaxometry. Bread was prepared from flours containing normal and atypical starches, e.g., flour from wheat line 5-5, with or without the inclusion of Bacillus stearothermophilus α-amylase. Initial crumb firmness increased with higher levels of AM or shorter AM chains. Both less extended AM and gluten networks and too rigid AM networks led to low crumb resilience. AP retrogradation during storage increased when crumb contained more AP or longer AP branch chains. Shorter AP branch chains, which were present at higher levels in 5-5 than in regular bread, were less prone to retrogradation, thereby limiting gluten network dehydration due to gluten to starch moisture migration. Correspondingly, crumb firming in 5-5 bread was restricted.


Assuntos
Amilopectina/química , Amilose/química , Pão/análise , Armazenamento de Alimentos , Amilopectina/metabolismo , Amilose/metabolismo , Proteínas de Bactérias , Farinha/análise , Geobacillus stearothermophilus/enzimologia , Glutens/química , Espectroscopia de Ressonância Magnética , Amido/química , Triticum/química , Água , alfa-Amilases/metabolismo
18.
Carbohydr Polym ; 235: 115846, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32122519

RESUMO

It is well established that amylose folds in a helix conformation in presence of lipids. Structural features of such molecular complexes are often analysed using 13C NMR spectroscopy. The large size of amylose used to make such analysis doesn't allow to unambiguously correlate structure of polymers and spectroscopic signals. We present structural analysis of small sized amyloses complexed to palmitic acid using classical molecular dynamics. 15 glucoses residues are necessary for the amylose to fold around the palmitic acid in a well-established helix conformation. Simulating 13C NMR spectra using quantum chemical DFT approach, we demonstrate that these spectra are affected by amylose size and specific intramolecular hydrogen bonds. By mean of theoretical NMR spectra of a 19-residues amylose, we precise the attribution of each characteristic resonances. One chemical shift that is usually attributed to a specific carbon may be related to the existence of different inter or intramolecular hydrogen bonds.


Assuntos
Amilose/química , Teoria da Densidade Funcional , Lipídeos/química , Simulação de Dinâmica Molecular , Espectroscopia de Ressonância Magnética , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
19.
Carbohydr Polym ; 234: 115892, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32070512

RESUMO

The limited reactivity of starch towards maleic anhydride (MA) affords maleate with a low degree of MA substitutions (CC and COOH groups). In this study, we investigated the relationship between the starch structure, controlled by its amylose (AM)/amylopectin (AP) ratio, and the DS of starch maleates using C4[mim]Cl as the recyclable media, and catalyst. The results indicated that starches with varying AM/AP ratio produced maleates with comparable CC groups (DSNMR = 0.06-0.07). Following dissolution, the high amylose (DStitration = 1.17, yield = 69.2 %) and regular starches (DStitration = 1.17; yield = 59.3 %) produced high DStitration maleates (COOH groups) at MA/AGU ratio of 12:1 (80 °C, 10 min). Comparatively, DStitration value of waxy starch maleates (DStitration = 0.88, yield = 59.3 %) was lower than AM-based starches, possibly due to the crosslinking tendency of AP branches consisting of carboxylic end-groups. Interestingly, DStitration value for EHCS (1.17) ranged between its bulk (DSNMR: 0.06) and surface distribution of MA (DSSXPS 1.7); therefore, we considered it reliable for future reference.


Assuntos
Amilose/química , Imidazóis/química , Anidridos Maleicos/química , Amido/química , Esterificação , Estrutura Molecular , Tamanho da Partícula , Propriedades de Superfície
20.
Food Chem ; 315: 126245, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32004980

RESUMO

Our objective was to investigate the correlation between processing conditions and structural properties of lotus seed starch-lecithin complexes by dynamic high-pressure homogenization and explore the formation mechanism. The complexes formed with 5% lecithin at 90 MPa had the highest complex index among samples, thus protecting the integrity of the particles. The complexes inhibited the degradation of amylopectin and retrogradation of amylose, and displayed different V6II-, V6I- and A-type crystalline patterns. Additionally, the double helix structure was enhanced with increasing pressure, and the addition of lecithin contributed to the formation of single-helix amylose-lecithin complexes. These complexes prevented the single helix structure of starch to further form double helix structures, as demonstrated by visual correlation analysis. Moreover, a formation mechanism was established, and lotus seed starch-lecithin complexes with V6I-type crystalline were formed under appropriate conditions, but a homogenization pressure either too low or too high was not conducive to complex formation.


Assuntos
Manipulação de Alimentos/métodos , Lecitinas/química , Lotus/química , Amido/química , Amilopectina/química , Amilose/química , Cromatografia em Gel , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Varredura , Pressão , Espalhamento a Baixo Ângulo , Sementes/química , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
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