| 1. |
- Bertoft, Eric
(författare)
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A Study of the Internal Structure in Cassava and Rice Amylopectin
- 2009
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Ingår i: Starch/Stärke. - : Wiley. - 0038-9056 .- 1521-379X. ; 61, s. 557-569
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Tidskriftsartikel (refereegranskat)abstract
- Cassava and rice amylopectins and their phi,beta-limit dextrins were debranched and the unit chain compositions were analyzed by gel permeation chromatography and high performance anion-exchange chromatography The content of amylose and super-long amylopectin chains was 15 5-15.6% and 0.8-1.2% in cassava and 15.1-18.7% and 3 4-8 6% in rice starches, respectively. The internal unit chain profiles of the amylopectin samples were obtained from the phi,beta-limit dextrins Shott B-chains were subdivided into a major group (BS(major)) with a degree of polymerization (DP) of 8-25 and a minor group of "fingerprint" B-chains (B(fp)) with DP 3-7. Cassava and rice amylopectins possessed different amounts and patterns of B(fp)-chains The rice samples contained higher amounts of B(fp)-chains, which suggested larger size of its. clusters when compared with cassava. The content of the shortest "fingerprint" A-chains (A(fp)) was also variable, especially between the rice cultivars The position of the internal chains in the original amylopectin chain profile was traced The reconstructed B-chain profiles fitted well with the original profiles. This implied that most of the B-chains carried external chain segments of similar lengths, which corresponded to the experimentally measured average length.
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| 2. |
- Contado, C, et al.
(författare)
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High-speed separation and size characterization of wheat and barley starch granules by lift-hyperlayer asymmetrical flow field-flow fractionation in synergy with SPLITT fractionation
- 2006
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 58:3-4, s. 140-154
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Tidskriftsartikel (refereegranskat)abstract
- The complementary employment of two separation techniques, one analytical-scale, the other preparative-scale, i.e. the lift-hyperlayer asymmetrical flow field-flow fractionation (AsyFIFFF) and the split flow-thin cell (SPLITT) is presented for the first time as a methodology to size-separate and rapidly characterize starch granules of different botanical origins. Very rapid separation and size characterization is achieved by AsyFIFFF and the techniques are mutually used to characterize and confirm data produced by the other. Light microscopy (LM) was used to test the quality of the performed SPLITT separations and consequently to evaluate the AsyFIFFF results. The procedure was applied to wheat and barley starch.
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| 3. |
- Duanmu, Jie, et al.
(författare)
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Synthesis and preparation of crosslinked allylglycidyl ether-modified starch-wood fibre composites
- 2007
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Ingår i: Starke (Weinheim). - : Wiley. - 0038-9056 .- 1521-379X. ; 59:11, s. 523-532
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Tidskriftsartikel (refereegranskat)abstract
- Native potato starch has been modified with allylglycidyl ether (AGE) under various reaction conditions including different sodium hydroxide and AGE concentrations, reaction temperatures and times. H-1-NMR and FT-IR were used to analyze the products. AGE-modified starch, with two degrees of substitution (DS), namely DS = 1.3 and DS = 2.3, was synthesized and used for preparation of a new family of crosslinked composites reinforced with various amounts of bleached softwood fibres. Composite premixes of modified starch, wood fibres and ethylene glycol dimethacrylate (EGDA) were cured in a hot press using 2% (w/w) of benzoyl peroxide at 150 degrees C under high pressure for 10 min. The matrix with high degree of substitution exhibited good processability and was easily processed even for the highest fibre contents, up to 70% (w/w). In addition, scanning electron micrographs showed good dispersion and adhesion between the starch matrix with high degree of substitution and fibre. The original poor mechanical properties of the cured modified starch were markedly improved by the addition of wood fibres. In the extractions tests cured high-DS and low-DS composite samples showed weight losses in the range of 1 and 15% (w/w), respectively. No unreacted crosslinker ethylene glycol dimethacrylate was detected in the solutes as determined by NMR.
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| 4. |
- Ekanayakea, S, et al.
(författare)
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Effect of processing of sword beans (Canavalia gladiata) on physicochemical properties of starch
- 2006
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 58:5, s. 215-222
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Tidskriftsartikel (refereegranskat)abstract
- The effect of various processing methods on physico-chemical properties of sword bean starch was studied. Seed grits and flour were cooked with and without soaking, wet-autoclaved, and roasted. The changes in starch associated with these processing methods were studied by observing changes in granular structure, water solubility index, water absorption index, molecular size distribution and the degree of gelatinization estimated by differential scanning calorimetry. Intact, ungelatinized starch granules of raw and dry-heat treated samples were observed under the light microscope. The starch granules were elliptical in shape and had an average length and breadth of 37-40 mu m and 27 mu m, respectively. Wet-processed samples had the lowest water solubility, higher water absorption and lower gelatinization enthalpies than the raw bean flour, whereas the dry heat-treated samples showed higher water solubility and higher gelatinization enthalpies. The starch molecular size distribution pattern showed a higher amount of high molecular size carbohydrates in dry heat-treated samples and a large fraction of intermediate molecular size carbohydrates in the wet-processed samples. The low molecular size carbohydrate content was low in wet-processed samples where processing was done with excess water.
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| 5. |
- Elfstrand, Lidia, et al.
(författare)
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From starch to starch microspheres: Factors controlling the microspheres quality
- 2006
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 58:8, s. 381-390
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Tidskriftsartikel (refereegranskat)abstract
- Starch microparticle is a dosage form suitable for encapsulation of protein drugs. The microparticle characteristics can be influential factors for consecutive sustained drug release from the starch matrix and impact its ability to be coated by poly(D,L-lactide-co-glycolide). In this study, six types of starch microparticles were investigated and characterized. Desired qualities of the microspheres such as spherical form of the particles, well-defined and sharp particle contours were coincident with coarse surface morphology, sharp and distinct peaks in DSC and X-ray graphs. It was concluded that the quality of the starch microparticles was influenced by molecular properties of the starch material as well as type of buffer, and these factors were related to recrystallization kinetics, amount and quality of ordered/crystalline structure of final starch microspheres and their microscopic appearance.
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| 6. |
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| 7. |
- Jonhed, Anna, 1975-, et al.
(författare)
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The interaction between surfactants and 2-hydroxy-3-(N,N-dimethyl-N-dodecylammonium) propyloxy starches
- 2006
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Ingår i: Starch. - : Wiley. - 1521-379X. ; 58:11, s. 561-571
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Tidskriftsartikel (refereegranskat)abstract
- The phase behavior of temperature-responsive hydrophobically modified starches and the interaction between oxidized potato amylose and hydrophobically modified potato amylopectin have been investigated by rheology, turbidity measurements and differential scanning calorimetry. When oxidized amylose was mixed with hydrophobically modified amylopectin, a viscosity peak was observed, indicative of a guest-host interaction between the oxidized amylose and the hydrophobically modified amylopectin. A series of oxidized and hydrophobically modified potato starches were investigated in the presence of an anionic and cationic surfactant. A coil-helix transition of the investigated starches was observed in the presence of surfactant, with the exception of a cationic surfactant combined with a hydrophobically modified zwitterionic starch of high positive net charge. The destabilizing mechanism (the phase separation) of the hydrophobically modified starches was studied as well as the difference in stabilizing capacity between the investigated cationic and anionic surfactants.
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| 8. |
- Melander, Claes, et al.
(författare)
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Hydrolysis of maltoheptaose in flow through silicon wafer microreactors containing immobilised alpha-amylase and glycoamylase
- 2006
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 58:5, s. 231-242
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Tidskriftsartikel (refereegranskat)abstract
- In this study,a silicon micro immobilised enzyme reactor (mu IMER) has been applied for hydrolysis of maltoheptaose as a model maltodextrin and starch using immobilised otamylase (from Aspergillus oryzae) and glycoamylase (from Aspergillus niger). The influence of several parameters was investigated such as immobilisation chemistry, buffer constituents, pH, temperature, flow rate and substrate concentration. The conversion efficiency profile of the substrate was measured and the long-term stability of the reactor was tested. For separation and detection of the formed hydrolysis products, high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was used. The results show that the mu IMERs can also be used for hydrolysis of starch and also additionally be connected directly on-line with, e.g., liquid chromatography, making it possible to perform on-line characterisation and analysis of starch hydrolysis products.
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| 9. |
- Modig, Gustaf, et al.
(författare)
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Influence of jet-cooking temperature and ionic strength on size and structure of cationic potato amylopectin starch as measured by asymmetrical flow field-flow fractionation multi-angle light scattering
- 2006
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 58:2, s. 55-65
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Tidskriftsartikel (refereegranskat)abstract
- Asymmetrical flow field-flow fractionation (AsFIFFF) in combination with multi-angle light scattering (MALS) was applied to cationic potato amylopectin (CPAP) to investigate how molar mass, root-mean-square (r.m.s.) radius and shape was influenced by different conditions of jet-cooking. The effect of different jet-cooking temperatures in the range 110 degrees C - 140 degrees C was studied in an excess steam jet-cooker. This equipment is used in the industry for dissolution of starch and starch derivatives before technical application. The effect of different ionic strengths conditions was examined in the range of 10-200 mM. The weight-average molar mass decreased from about 34 x 10(7) g/mol to 2.6 x 10(7) g/mol when the jet-cooking temperature was increased from 110 degrees C to 140 degrees C. Concurrently the root-mean-square radius decreased from ca 380 nm to 90 nm. The decrease in size was reflected by a decrease in viscosity with increasing temperature. The root-mean-square radius was reduced when increasing the ionic strength. This decrease in size was correlated with a decrease in viscosity. Conformation and Kratky plots showed that at low ionic strength (<= 10 mM) CPAP behaved as a flexible chain with high degree of branching, close to hyperbranching. Increase of the ionic strength gave a more compact structure and changes in the internal structure were observed as well. Consequently, by using AsFIFFF - MAILS the effect of technical processing on the molar mass, molecular radius, conformational structure, and shape could be determined in a size region where standard methodology commonly fails.
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| 10. |
- Moorthy, SN, et al.
(författare)
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Determination of amylose content in different starches using modulated differential scanning calorimetry
- 2006
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 58:5, s. 209-214
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Tidskriftsartikel (refereegranskat)abstract
- A simple calorimetric method for determination of amylose content in starch is reported. Starches were heated in the presence of two common surfactants, viz., sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB), and the enthalpies of melting of the amylose-surfactant complexes were determined using Modulated Differential Scanning Calorimetry (MDSC). A large number of native starches including cereal, root and pea starches were examined. The results were compared with those obtained by iodimetry and gel permeation chromatography (GPC) for all the starches. There was a good correlation between the values from iodimetry and GPC with those obtained using the surfactants. Both surfactants seemed to work equally well, even for those starches with about 40% amylose content. However, in case of SIDS higher standard deviations were usually obtained than for CTAB in the determination of transition enthalpies.
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