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| 2. |
- Ortega-Ojeda, Fernando, et al.
(författare)
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On the dispersion and small-amplitude oscillation measurements of high amylopectin potato starch.
- 2003
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 55:3-4, s. 121-121
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Tidskriftsartikel (refereegranskat)abstract
- Differential scanning calorimetry (DSC), optical microscopy and turbidity measurements were used to define experimental conditions (time, temperature and shearing) for dissolving high amylopectin potato starch (HAPP) granules. A simple, less time consuming and non-chemical method for preparing starch samples was established. Small-amplitude oscillation measurements were used to characterise the behaviour of the resulting solutions. The DSC, microscopy and turbidity experiments showed that preparing the samples at 140 °C was necessary to dissolve HAPP, with no further detectable granule structures. Rheological measurements showed that the storage (G') and loss (G'') moduli increased with concentration. At a HAPP concentration of 2 % G'' > G' and the system behaved like a diluted solution. The frequency dependence also decreased with increasing concentration. At 14 % HAPP, the system showed more gel-like properties with G' more or less independent of frequency.
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| 3. |
- Richardson, G., et al.
(författare)
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Wheat starch gelatinization : The effects of sucrose, emulsifier and the physical state of the emulsifier
- 2003
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Ingår i: Starke (Weinheim). - 0038-9056 .- 1521-379X. ; 55:42067, s. 150-161
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Tidskriftsartikel (refereegranskat)abstract
- The effect of emulsifier and/or sucrose on the swelling of an 8% wheat starch dispersion was evaluated by microscopy. Visual observations of smeared starch pastes under the light microscope, image analysis of the starch granule sizes and viscosity measurements of the starch paste during heating were combined to explain the effects of the added ingredients. Sucrose (12 or 24%, w/w) was shown to delay the swelling of the granules at least up to 50°C. Above this temperature, the leakage of amylose and granule fragmentation were delayed, but the swelling itself seemed to be accelerated. The polyglycerol ester emulsifier (PGE/MG) at concentrations of 0.5 and 4.0% hindered amylose leakage completely up to 90°C, followed by a sudden granule rupture. The size of the granules increased up to about 70°C, but not above this temperature. The monoglyceride (MG) emulsifier in ?-form already had a restrictive effect on the swelling at low temperatures, while the same emulsifier in ?-form did not restrict the swelling until higher temperatures were reached. The emulsifier itself converted into the lamellar state at between 55 and 70°C, irrespective of the initial form, but the final viscosity was higher in the paste with MG in ?-form. Thus, the initial physical state of the emulsifier was shown to have an influence on the final properties of the gel. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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| 4. |
- Sajeev, MS, et al.
(författare)
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Gelatinisation characteristics of cassava starch settled in the presence of different chemicals
- 2003
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 55:5, s. 213-221
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Tidskriftsartikel (refereegranskat)abstract
- Addition of chemicals during the extraction of cassava starch for enhancing the settling rate, whiteness and compactness of the settled starch is an accepted commercial practice. The effect of addition of selected chemicals such as acids (sulphuric and hydrochloric acids), bleaching and oxidising agents (sodium metabisulphite and sodium hypochlorite) and alum during settling on the thermal and pasting properties of the cassava starch was examined. Treatment with sulphuric acid produced a noticeable increase in all DSC gelatinisation parameters, viz. onset gelatinisation temperature (T-o), temperature at peak minimum (T-p) and end temperature (T-e), with increasing concentration of acid, while only a marginal shift could be obtained even at higher concentration of hydrochloric acid. However, no major effect resulted from treatment with sodium metabisulphite, sodium hypochlorite and alum. The gelatinisation enthalpy was hardly affected by the treatments. An exception was hydrochloric acid, which brought about a perceptible decrease in enthalpy at higher concentrations indicating that starch crystallinity is influenced to a small extent by hydrochloric acid. Pasting characteristics studied using a Rapid Visco Analyser showed that sulphuric acid, even at the lowest concentration (5 mM), considerably affected the structural characteristics of cassava starch, while hydrochloric acid induced similar effect only at higher concentrations. Alum reduced the paste viscosity while the bleaching agents (sodium metabisulphite and sodium hypochlorite) were not so effective in modifying the starch viscosity characteristics.
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| 5. |
- Tufvesson, Fredrik, et al.
(författare)
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Formation of amylose-lipid complexes and effects of temperature treatment. Part 1: Monoglycerides.
- 2003
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 55:2, s. 61-71
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Tidskriftsartikel (refereegranskat)abstract
- The formation of amylose-lipid complexes of form I (amorphous structure) and form II (crystalline structure) during heating was studied by differential scanning calorimetry (DSC) for a range of monoglycerides and for monoglyceride mixtures. The temperature treatment applied to amylose-monoglyceride-mixtures were either the first scan in DSC (10 °C/min, 15-144 °C) or a prolonged heat treatment where the samples were kept at 100 °C for 24 h before being analysed in DSC. The temperature treatment influenced which type of complex was formed, and how much, whereas the thermal stability (as judged from the transition peak temperature) was only marginally influenced. It is shown in this study that all the investigated monoglycerides were able to give complex form I as well as complex form II, although the conditions for the formation differed between the monoglycerides. It was found that a simple DSC-scan was enough for formation of complex form II for the shortest monoglycerides (glycerol monocaprin, glycerol monolaurin and glycerol monomyristin), whereas in case of the longer monoglycerides and monoglyceride mixtures the prolonged heat treatment was required for formation of complex form II. Moreover, the monoglyceride mixtures gave only form II at conditions where the individual components in the mixtures gave both form I and form II.
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| 6. |
- Tufvesson, Fredrik, et al.
(författare)
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Formation of amylose-lipid complexes and effects of temperature treatment. Part 2. Fatty acids.
- 2003
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Ingår i: Stärke. - : Wiley. - 0038-9056. ; 55:3-4, s. 138-149
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Tidskriftsartikel (refereegranskat)abstract
- This article is the second part of research on amylose-lipid complexes, where the first article dealt with monoglycerides. Here, a variety of fatty acids with chain lengths between 3 and 22 carbons and with varying degree of unsaturation were studied regarding their ability to form amylose-lipid complexes. In the present paper it is intended to investigate the formation of different fatty acid- amylose complexes under conditions that are not optimised for complex formation. Such conditions are common in the processing of starch. Differential scanning calorimetry (DSC) was used to analyse transition temperatures and enthalpies (H). The transition enthalpy H was taken as a measure of the quantity of the complexes in the samples. Except for the two shortest fatty acids (propionic and butyric acid), all the fatty acids showed DSC-peaks corresponding to transition of amylose-lipid complexes. Form II complexes, i.e. the crystalline form of the complex, were also formed for all fatty acids with a chain length of 12, even with polyunsaturated fatty acids. In this investigation, the amount and type of complexes formed do not reflect equilibrium conditions, but are instead a result of the rate of all the different sub-processes involved in complex formation, and these are influenced by the availability of the fatty acids and the heat treatment. The highest amounts of complexes were created by arachidonic and docosahexaenoic acid when the sample had not been subjected to any previous heat treatment. Heat treatment of the sample changed this and for heat treated samples the saturated palmitic and stearic acid yielded highest total amount of complexes. However, the ratio between complexes of form II and form I differed between the fatty acids complexes and during extended temperature treatment, most form II complexes were created by arachidonic and linoleic acid. Comparing the results from each fatty acid to the corresponding monoglyceride (with chain lengths of 10-18), it can be concluded that fatty acids seem to form complexes more easily than monoglycerides do, but monoglycerides create complex form II more easily than fatty acids, especially in case of shorter-chain lipids.
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