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1.
Int J Biol Macromol ; 155: 226-232, 2020 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-32224181

RESUMO

Colored brown rice shows better health benefits than polished rice, and there is great interest in the design of demanded cooking manners for brown rice. This investigation concerns how the change of cooking mode can slow starch digestion of colored brown rice by inspecting mainly starch structural changes during cooking. Compared to cooking Mode 1, the soaking of Mode 2, at higher temperature, probably enhanced water diffusion into rice matrices, thus strengthening starch lamellae without apparently altering rice morphology and ordered structures such as starch polymorphs and helices. The followed heating of Mode 2, with reduced time, more sufficiently disrupted rice structures, causing less prominent nonperiodic molecular organizations. At the final cooking stage, the braising of Mode 2, having faster temperature reduction for prolonged time, leading to similar rice morphology, reduced molecular orders (e.g., helices) and probably denser amorphous regions of nonperiodic organizations. Such features tended to increase packing density of molecular chains (mainly starch) in rice matrices, thus slowing the enzyme diffusion in rice matrices and associated binding and catalysis events. In this way, a reduced starch digestion rate and increased resistant starch (RS) and slowly digestible starch (SDS) were seen for the rice following Mode 2 cooking.

2.
Int J Biol Macromol ; 144: 373-379, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31843614

RESUMO

This work concerns the multi-scale structures and digestion behaviors of indica rice starches with apparent amylose contents (AACs) of ca. 14%-24%. A higher AAC not always allowed a lower digestion rate (k), different from previous findings that starches containing more amylose normally show slowed digestion. Here, the proportion of stable molecular orders (melting temperature above ca. 73 °C) and AAC synergistically governed starch digestion rate. With a similar AAC, a higher amount of stable orders (Rh/l, ratio of enthalpy of stable orders to that of the rest) led to a lower k. Also, with a similar Rh/l, a larger AAC caused a lower k. Consistently, JPZ starch had almost the highest AAC and Rh/l, showing the lowest k. Regarding this, amylose and stable orders played roles in increasing the bulk density of starch structure matrices, and eventually slow the diffusion, absorption and catalysis events of digestion enzymes within the matrices.

3.
Polymers (Basel) ; 11(12)2019 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-31783690

RESUMO

Different characterization methods spanning length scales from molecular to micron scale were applied to inspect the microstructures and mechanical/hydrophilic features of agar/konjac glucomannan (KGM) films prepared under different drying temperatures (40 and 60 °C). Note that the lower preparation temperature (40 °C) could increase the strength and elongation of agar/KGM films at high KGM levels (18:82 wt/wt KGM-agar, or higher). This was related to the variations in the film multi-scale structures with the increment of KGM content: the reduced crystallinity, the increased perfection of nanoscale orders at some KGM amounts, and the negligibly-changed morphology and molecular chemical structure under 40 °C preparation temperature. These structural changes initially decreased the film tensile strength, and subsequently increased the film strength and elongation with increasing KGM content. Moreover, under the higher drying temperature (60 °C), the increased KGM content could concurrently reduce the strength and elongation for the films, associated with probable phase separations on nano and smaller scales. In addition, the increased KGM amount tended to make the film more hydrophilic, whereas the changes in the film structures did not dominantly affect the changing trend of hydrophilicity.

4.
Int J Biol Macromol ; 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31759009

RESUMO

This work inspects the supramolecular/molecular structures and digestion rate of potato starches (BEM, C7H, CP2 and CP4) as affected by starch biosynthetic enzymes. Among the starches, CP2 had a lower digestion rate with a higher paste heating stability. Regarding this, predominantly enzyme-sets (i) and (ii) were revealed to produce amylopectin chains. For CP2, the reduced activity ratio of starch-branching enzymes to soluble starch synthases allowed more long amylopectin chains (polymerization degree ≥ 34). Such molecular features tended to increase the crystallites and thicken the lamellae. With similar surface morphology and amylose content, the bulk density of chain packing in CP2 supramolecular structures could be increased. Then, there were an increase in the resistance of starch structures to hydrothermal effects, and a reduction in the enzyme hydrolysis rate. Also, the increased long amylopectin chains played roles in increasing the paste stability during heating with shearing and in reducing the digestion rate.

5.
Food Chem ; 295: 475-483, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31174784

RESUMO

By inspecting starch hierarchical structural evolutions, this work explores how microwave cooking with storage tailors the slowly digestible features of indica (IRS) and waxy (WRS) rice starches. Particularly, relative to conventional cooking-storage, the microwave treatment especially at high powers (8 and 10 W/g) increased the molecular orders (crystallites) and periodic amorphous-crystalline structures. Such changes facilitated the formation of domains with intermediately-densely packed starch chains, being modestly accessible to the diffusion, absorption and catalysis of enzymes and dominantly showing slowly digestible features. Consistently, the microwave processed starches showed a higher SDS (slowly digestible starch) level and a lower digestion rate. This microwave-enhanced SDS generation became more prominent for IRS, and the treated IRS at 10 W/g showed the highest SDS content (ca. 54%). This is related to the enhanced reassembly of glucan chains into ordered/semicrystalline structures and the formation of slowly digestible domains as induced by the increase of amylose molecules.


Assuntos
Culinária/métodos , Armazenamento de Alimentos/métodos , Micro-Ondas , Oryza/química , Amido/química , Digestão , Amido/farmacocinética , Difração de Raios X
6.
Int J Biol Macromol ; 135: 437-444, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31145960

RESUMO

From a supramolecular structure viewpoint, we concern how concurrent microwave and heat moisture treatment (M/HMT) tailors the pasting and digestion features of indica rice starch (IRS) and waxy rice starch (WRS), using combined analytical methods such as scanning electron microscopy and small-angle X-ray scattering. The results confirm that, for the starches (especially IRS), M/HMT led to a concave granule surface, weakened alignment of helices in lamellae, loosened packing of chains in amorphous regions, and somewhat disrupted crystallites. Consequently, the susceptibility of starch structures to hydrothermal effects was insignificantly altered, as reflected by unchanged pasting temperature; the enzyme absorption/hydrolysis could be properly accelerated, as affirmed by a modestly increased digestion rate and slightly reduced enzymatic resistance. Also, compared to WRS, IRS had more amylose with relatively long branches, which probably contributed to starch chain interactions during M/HMT. This tended to reduce the paste viscosity related to the swelling degree of starch granules, and increase the paste stabilities during heating and cooling related to the robustness of swelled granules and the reorganization of glucan chains.


Assuntos
Digestão , Temperatura Alta , Micro-Ondas , Oryza/química , Amido/química , Hidrólise , Pomadas , Amido/metabolismo , Viscosidade
7.
J Agric Food Chem ; 67(22): 6302-6312, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-30925057

RESUMO

Granule-bound starch synthase I (GBSSI) and starch-branching enzymes I and II (SBEI and SBEII) are crucial enzymes that biosynthesize starches with varied apparent amylose contents and amylopectin branching structure. With a sweet potato ( Ipomoea batatas [L.] Lam. cv. Xushu22), this work shows that downregulating GBSSI (for waxy starch) or SBE (for high-amylose starch) activity allowed the formation of new semicrystalline lamellae (named Type II) in sweet potato starch in addition to the widely reported Type I lamellae. Small-angle X-ray scattering (SAXS) results show that, compared with Type I lamellae, Type II lamellae displayed increased average thickness and thickness-distribution width, with thickened amorphous and crystalline components. The size-exclusion-chromatography (SEC) data revealed mainly two enzyme sets, (i) and (ii), synthesizing amylopectin chains. Reducing the GBSSI or SBE activity increased the amounts of amylopectin long chains (degree of polymerization (DP) ≥ 33). Combined SAXS and SEC analyses indicate that parts of these long chains from enzyme set (i) could be confined to Type II lamellae, followed by DP ≤ 32 short chains in Type I lamellae and the rest of the long chains from enzyme sets (i) and (ii) spanning more than a single lamella.


Assuntos
Enzima Ramificadora de 1,4-alfa-Glucana/genética , Ipomoea batatas/enzimologia , Proteínas de Plantas/genética , Sintase do Amido/genética , Amido/biossíntese , Amido/química , Enzima Ramificadora de 1,4-alfa-Glucana/metabolismo , Regulação para Baixo , Ipomoea batatas/genética , Ipomoea batatas/metabolismo , Proteínas de Plantas/metabolismo , Espalhamento a Baixo Ângulo , Sintase do Amido/metabolismo
8.
Carbohydr Polym ; 213: 199-207, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30879661

RESUMO

This work discloses the multi-scale structure and pasting/digestion behaviors of yam bean tuber starches (YB-GD and YB-SC). Compared to potato starch, YB starches exhibited varied pasting/digestion features that were understood from a multi-scale structural view. Especially, YB starches showed relatively polydisperse lamellae, less perfect crystallites, and fewer amylose molecules. These features should reduce the bulk density of starch chain packing, and could facilitate the water or enzyme diffusion in starch matrixes. Consistently, not only was starch's resistance to hydrothermal effects weakened (shown by reduced pasting temperature), but also the enzyme absorption to starch chains and the subsequent hydrolysis events were accelerated. Furthermore, YB starch molecules had more short chains, which played roles in reducing the paste viscosity along with the reduced granule size and in enhancing the paste stabilities during heating and cooling. Also, those molecular features tended to speed up the enzyme diffusion and digestion events.


Assuntos
Pachyrhizus/metabolismo , Tubérculos/metabolismo , Amido/metabolismo , Configuração de Carboidratos , Pachyrhizus/química , Tamanho da Partícula , Tubérculos/química , Amido/química , Propriedades de Superfície
9.
Int J Biol Macromol ; 129: 679-685, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30738897

RESUMO

This work concerns how crosslinker amount (N, N'-methylene-bisacrylamide) affects the microstructural, absorbent and rheological features of one-step prepared starch-based superabsorbent polymers at a high starch concentration (0.27:1 w/w starch-water). The increased crosslinker amount evidently altered the microstructure and the absorbent and rheological features. Then, the variations in starch-based superabsorbent polymer properties were discussed from a microstructure viewpoint. Particularly, the higher crosslinker quantity rose the crosslinking density and the ratio (GR) of grafted anhydroglucose unit on starch backbone (from 27% to 52%), but short the average polyacrylamide (PAM) chain length (LPAM). These structural features suppressed the chain stretch within starch-based superabsorbent polymer fractal gels (confirmed by smaller Rg value) and promoted the formation of smaller chain networks, thus weakening the water absorption to the starch-based superabsorbent polymer chain networks. Also, the increased GR and reduced LPAM, with lowered chain extension and elevated crosslinking density, probably decreased the flexibility and mobility of chain segments in starch-based superabsorbent polymer gel matrixes. This caused the enhanced robustness and storage modulus of the gels with reduced chain energy dissipation ability.


Assuntos
Absorção Fisico-Química , Amido/química , Acrilamidas/química , Cério/química , Reologia , Água/química
10.
Food Chem ; 271: 102-108, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-30236653

RESUMO

Herein, we concern the multi-scale structure and properties (digestibility and pasting) of highland barley starch following heat moisture treatment (HMT). With the moisture content (MC) rose, HMT reduced the molecular weight (molar mass) but increased the amylose content and the V-type polymorph. When the MC was lower than 25%, a higher MC resulted in increases in the long- (crystallites) and short-range orders (double helices, etc.); nonetheless, a further elevated MC (i.e., 30%) tended to reduce the amounts of these ordered structures. Also, the SAXS results reveal that the lamellar structure could be gradually vanished by the increased MC. These structural changes on multiple scales transformed part of rapidly digestible starch into the slowly digestible and/or resistant forms, accompanied by higher pasting temperature and lower paste viscosity. Hence, highland barley starch following HMT can serve as a food ingredient with reduced digestion rate and paste viscosity.


Assuntos
Hordeum/química , Temperatura Alta , Amido/química , Amilose , Espalhamento a Baixo Ângulo , Viscosidade , Difração de Raios X
11.
J Sci Food Agric ; 99(5): 2158-2164, 2019 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-30302766

RESUMO

BACKGROUND: A decreasing freshness occurrs in Ctenopharyngodon (C.) idellus during post-mortem storage. In the present study, chitosan-glucose Maillard reaction products (CG-MRPs) were prepared by heating chitosan and glucose at different reaction temperatures and then used for preserving the freshness and quality of C. idellus fillets during cold storage (4 °C). RESULTS: High temperature enhanced the chitosan-glucose Maillard reaction and promoted the accumulation of melanoidins and intermediate compounds. The reducing power of CG-MRPs increased with an increasing reaction temperature. CG-MRPs inhibited the microbial growth rate and retarded the oxidation of proteins, lipids and nucleotides in C. idellus fillets by suppressing total bacterial count, total volatile basic nitrogen, thiobarbituric acid reactive substances and K values during cold storage. Furthermore, CG-MRPs prolonged shelf-life. The fillets treated with the CG-MRPs prepared at 120 °C showed an especially longer shelf-life (7 days). The preservative effect of CG-MRPs on fillets was the result of antibacterial components (melanoidins, reductone and furfural) in CG-MRPs and a reducing power against the oxidative degradation of proteins, nucleotides and lipids in C. idellus fillets. CONCLUSION: The present study demonstrates that, for C. idellus fillets, treatment with CG-MRPs prepared at 120 °C for 40 min could be a feasible approach for maintaining the freshness of C. idellus fillets and prolonging shelf-life during cold storage. © 2018 Society of Chemical Industry.


Assuntos
Quitosana/química , Produtos Pesqueiros/análise , Conservação de Alimentos/métodos , Conservantes de Alimentos/química , Glucose/química , Produtos Finais de Glicação Avançada/química , Animais , Carpas , Conservação de Alimentos/instrumentação , Armazenamento de Alimentos , Temperatura Alta , Humanos , Reação de Maillard , Paladar
12.
Int J Biol Macromol ; 121: 882-888, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30342129

RESUMO

With screening of Lactobacillus fermentum M9 and Candida santamariae Y11 from a natural fermentation broth (Jinjian) for rice noodle production, this work concerns how fermentation with M9:Y11 suspensions of different volume ratios affects the texture and sensory features of rice noodles. The M9:Y11 strains regulated rice structures and thus the physicochemical features of rice noodles. In particular, 5:5 and 8:2 v/v M9:Y11 strains endowed rice noodles with better texture and sensory performance than did Jinjian. The underlying mechanism regarding evolutions in rice noodle properties was discussed from a rice structural view. Specifically, the fermentation disrupted rice ordered structures (e.g., starch crystallites) and broke starch granules, which was preferable for the swelling and molecule leaching of rice noodle matrixes with enhanced molecule interactions. Such noodle matrixes were robust to resist imposed force, thus exhibiting increased hardness, chewiness and mouthfeel. More interestingly, the 5:5 and 8:2 v/v M9:Y11 strains less prominently altered starch granule integrity, contributing to increasing hardness, chewiness and mouthfeel of rice noodles associated with robustness of swollen granule shell within rice gel matrixes. These two ratios of M9:Y11 strains also improved the color, aroma and taste for rice noodles.


Assuntos
Candida/metabolismo , Fermentação , Lactobacillus/metabolismo , Oryza/química , Oryza/microbiologia , Amido/química , Manipulação de Alimentos , Paladar
13.
Int J Biol Macromol ; 116: 793-800, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29778877

RESUMO

Using combined analytical techniques, this work discloses how citric acid (CA) treatment affects the pasting features of starch from a view of multi-scale structural evolutions. The treatment induced disruption events in starch multi-level structures and thus modulated the pasting behaviors. A structure-property relationship was proposed to rationalize CA effects on starch pasting properties. Specifically, CA disrupted starch structures from molecular scale to micron scale, eventually reducing pasting temperature and paste viscosities. Interestingly, unlike previous findings that acid hydrolysis normally reduces the breakdown viscosity, the CA here resulted in regulated breakdown viscosity (paste stability under shearing and heating) related to concurrent effects from granule surface corrosion and molecule degradation. Moreover, the molecule degradation of starch weakened its chain rearrangement tendency, allowing increased paste stability during cooling. Also, simply altering CA concentration effectively regulated starch structural and pasting features. Hence, compared to untreated counterpart, the CA-treated starch may serve as food agents with reduced paste viscosity, regulated paste stability under heating and increased paste stability during cooling.


Assuntos
Ácido Cítrico/química , Oryza/química , Amido/química
14.
Int J Biol Macromol ; 112: 761-766, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29410072

RESUMO

The surface hydrophobicity of starch-based films could be regulated using a two-step surface modification method. Such modification was realized by grafting with alkanols of different chain lengths (hexanol, dodecanol and octadecanol) on the surface of starch-based films. The grafting of alkanol increased the mobility of glycerol as the plasticizer within the film surface. Also, this grafting increased the mass ratio of carbon to oxygen on the film surface but reduced the mass ratio of carbon to nitrogen. Under the same reaction conditions, there were fewer dodecyl chains grafted onto the film surface than hexyl or octadecyl chains. Furthermore, the results revealed that the surface hydrophobicity of starch-based films could be enhanced by simply increasing the alkyl chain length. Also, fewer alkyl chains tended to reduce the surface hydrophobicity of the films. These results are valuable for the rational design of starch-based materials with demanded hydrophobic properties.


Assuntos
Álcoois Graxos/química , Interações Hidrofóbicas e Hidrofílicas , Amido/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície
15.
Carbohydr Polym ; 181: 528-535, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29254003

RESUMO

This work discloses the multi-level structure and thermal behaviors of hydrophobic, propionylated starch-based films as affected by the amylose contents of starch materials used. Scanning electron microscopy results showed that amylose promoted the formation of more compact structure within the film matrices. Also, small and wide angle X-ray scattering analysis revealed that higher amylose content was preferable for the formation of new orders on nanoscale and crystallites. With these structural changes, the viscoelasticity of amorphous short chains was enhanced and the glass transition temperature was reduced by the increased amylose content; but the depolymerization of macromolecules and the decomposition of molecular bonds were postponed, since the increase in starch crystallites restricted the motion of adjacent amorphous regions. Hence, this work provides valuable information for rational design of hydrophobic starch-based films with desired thermal features by simply regulating the amylose content of starch raw materials.

16.
Nat Commun ; 8(1): 734, 2017 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-28963505

RESUMO

Sleep control is ascribed to a two-process model, a widely accepted concept that posits homoeostatic drive and a circadian process as the major sleep-regulating factors. Cognitive and emotional factors also influence sleep-wake behaviour; however, the precise circuit mechanisms underlying their effects on sleep control are unknown. Previous studies suggest that adenosine has a role affecting behavioural arousal in the nucleus accumbens (NAc), a brain area critical for reinforcement and reward. Here, we show that chemogenetic or optogenetic activation of excitatory adenosine A2A receptor-expressing indirect pathway neurons in the core region of the NAc strongly induces slow-wave sleep. Chemogenetic inhibition of the NAc indirect pathway neurons prevents the sleep induction, but does not affect the homoeostatic sleep rebound. In addition, motivational stimuli inhibit the activity of ventral pallidum-projecting NAc indirect pathway neurons and suppress sleep. Our findings reveal a prominent contribution of this indirect pathway to sleep control associated with motivation.In addition to circadian and homoeostatic drives, motivational levels influence sleep-wake cycles. Here the authors demonstrate that adenosine receptor-expressing neurons in the nucleus accumbens core that project to the ventral pallidum are inhibited by motivational stimuli and are causally involved in the control of slow-wave sleep.


Assuntos
Núcleo Accumbens/fisiologia , Sono/fisiologia , Animais , Ritmo Circadiano , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Motivação , Técnicas de Patch-Clamp , Proteínas Proto-Oncogênicas c-fos/metabolismo , Receptor A2A de Adenosina/metabolismo , Receptor A2A de Adenosina/fisiologia
17.
Carbohydr Polym ; 175: 141-148, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-28917849

RESUMO

From a microstructural view, the focus of this work was on the water absorption rate of starch-based superabsorbent polymers (starch-SAPs) prepared under high starch concentration (0.27:1w/w starch:water). The effects of starch amylose/amylopectin ratio were disclosed. The increase in amylopectin reduced the amount (CPAM) of polyacrylamide (PAM) in starch-SAPs but increased the ratio of starch carbons grafted with PAM, which eventually decreased the average length (LPAM) of PAM chains. The shorter PAM chains could reduce starch-SAP chain flexibility, thus inducing larger mass fractal gels in swollen starch-SAPs. In general, the increases in CPAM and LPAM were preferable for a higher water absorbent capacity (WAC), whereas the denser fractal gels reduced WAC. Interestingly, all starch-SAPs had a dual-phase absorption process with the first stage showing a higher rate than the second phase (k1>k2). The shorter PAM chains caused increases in k1 and k2.

18.
Int J Biol Macromol ; 104(Pt A): 837-845, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28684348

RESUMO

The multi-scale structures and pasting properties of starch in WWF were investigated after superfine grinding. Five particle size distributions of WWF and their corresponding starch were obtained. The grinding process reduced the particle size of WWF and starch. However, a slight increase of fragments from starch granules was observed with enhanced grinding strength because of the small decrease in starch particle size and the existence of other WWF components that undertook some of shearing force and friction during grinding. A prominent reduction in starch crystallinity was resulted due to the destruction of crystalline structure by grinding. Small-angle X-ray scattering analyses indicated the disordering in starch semi-crystalline lamellae with thinner lamellae thickness. Additionally, the 13C Nuclear Magnetic Resonance spectra demonstrated the alterations in starch chain conformation by varying peak areas of starch carbons (C1 and C4). Along with these structural changes, Starch pasting characteristics showed substantial variations, indicating decreased viscosities and higher pasting stability. The results suggest that the grinding treatments influenced the structures and pasting properties of starch even at a non-separated state, the changes in starch structures were related to the variations in starch gelatinization characteristics.


Assuntos
Farinha , Manipulação de Alimentos/métodos , Fenômenos Mecânicos , Amido/química , Triticum/química , Pomadas , Tamanho da Partícula
19.
Food Chem ; 233: 450-456, 2017 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-28530598

RESUMO

Here we concern the molecular fine structure of intermediate material (IM) fraction in regular maize starch (RMS) and Starpro 40 maize starch (S40). IM had a branching degree and a molar mass (Mw) somewhere between amylopectin (AP) and amylose (AM). Compared with AP, IM had more extra-long (Fr I) and long (Fr II) chains and fb3-chains (degree of polymerization (DP)>36), with a higher average chain length (CL). Also, IM contained less A-chains but more B-chains (both BS-chains with DP 3-25 and BL-chains with DP≥26), accompanied by longer B- and BL-chains, total internal chains (TICL) and average internal chains (ICL), and a similar average external chain length (ECL). Furthermore, relative to RMS-IM, the IM of S40 (with higher apparent amylose content than RMS) showed increases in relatively-long chains, e.g., Fr II, fb3-chains and BL-chains, but reductions in Mw, relatively-short chains (those with DP 6-12, etc.).


Assuntos
Amido/química , Zea mays/química , Amilopectina/química , Amilose/química , Estrutura Molecular
20.
Int J Biol Macromol ; 103: 152-157, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28476597

RESUMO

With synchrotron small/wide-angle X-ray scattering (SAXS/WAXS), we revealed that post-harvest hydration at ambient conditions can further alter the starch crystalline structure. The hydration process induced the alignment of starch helices into crystalline lamellae, irrespective of the starch type (A- or B-). In this process, non-crystalline helices were probably packed with water molecules to form new crystal units, thereby enhancing the overall concentration of starch crystallinity. In particular, a fraction of the monoclinic crystal units of the A-type starches encapsulated water molecules during hydration, leading to the outward movement of starch helices. Such movement resulted in the transformation of monoclinic units into hexagonal units, which was associated with the B-type crystallites. Hence, the hydration under ambient conditions could enhance the B-polymorphic features for both A-type and B-type starches. The new knowledge obtained here may guide the design of biopolymer-based liquid crystal materials with controlled lattice regularity and demanded features.


Assuntos
Amido/química , Cristalização , Espalhamento a Baixo Ângulo , Síncrotrons , Temperatura , Água/química , Difração de Raios X
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