| 1. |
- Lundin, Leif, et al.
(författare)
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Influence of locust bean gum on the rheological behaviour and microstructure of K-?-carrageenan
- 1995
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 28:2, s. 91-99
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Tidskriftsartikel (refereegranskat)abstract
- Mixtures of ?-carrageenan-locust bean gum (LBG) were analysed by transmission electron microscopy and dynamic viscoelastic measurements. The effect of two different mannose:galactose (M:G) ratios of LBG on the rheology and microstructure of ?-carrageenan in KCl was studied. The rheological differences observed in the mixed gel as LBGs were added were found to be dependent on M:G ratio, salt concentration and LBG content. Monolayers of dilute samples of ?-carrageenan mixed with LBGs in varying ratios in 0.10 M KCl were visualised by low-angle rotary metal shadowing for transmission electron microscopy. The results obtained showed that LBG hindered the self-association of ?-carrageenan, and that the effect was enhanced at a higher M:G ratio and as the LBG contents were increased. Small deformation viscoelastic measurements were performed on ?-carrageenan-LBG mixtures in 0.050 and 0.10 M KCl at constant temperatures of 38 and 48 °C, respectively. Increased rheological stability was observed for mixtures containing a relatively high LBG content. Mixtures with a relatively low LBG content showed a maximum in storage modulus and an increase in phase angle. The stabilising effect of LBG on the rheology of the blends was more effective for the LBG with high M:G and as the LBG content was increased. © 1996.
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| 2. |
- Lundin, Leif, et al.
(författare)
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Supermolecular aspects of xanthan - locust bean gum gels based on rheology and electron microscopy
- 1995
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Ingår i: Carbohydrates polymer. - 0346-718X .- 0144-8617 .- 1879-1344. ; 26:2, s. 129-40
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Tidskriftsartikel (refereegranskat)abstract
- The viscoelastic properties and supermolecular structure of synergistic gels, formed by xanthan and locust bean gum (LBG) of two different mannose:galactose ratios (M:G), have been investigated by small deformation viscoelastic measurements and by low angle rotary-shadowing for transmission electron microscopy. The rheological properties at 20°C for mixtures subjected to heating and cooling cycles in the temperature range 30-80°C were found to be dependent on the M:G ratio. Mixtures of xanthan and LBG mixed at temperatures ?40°C were found to form true gels with low phase angles. Blends of xanthan and LBG with a low M:G ratio did not show any increase in synergistic effects as the temperature was increased, whilst the mixture of xanthan and LBG with a high M:G ratio showed a strong increase in synergistic effects as the temperature was raised above 60°C. A difference in gelation temperature (Tg) of approx.13°C was observed between the mixtures of xanthan and the two LBG fractions. The Tg for xanthan with a high M:G ratio was approx. 53°C, whilst the Tg for mixtures of xanthan and LBG with a low M:G ratio was approx. 40°C. Results obtained using electron microscopy showed that the xanthan-LBG network was formed from xanthan supermolecular strands, and addition of LBG did not influence the xanthan structure. The observed structural features of the gels were independent of heat treatment and LBG fraction. The structural similarities and rheological differences observed between xanthan and the LBG fractions are discussed in comparison with existing interaction models at the molecular level. Based on these results, a speculative network model at the supermolecular level is presented.
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| 3. |
- Lundin, Leif, et al.
(författare)
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Rheology and microstructure of Ca- and Na-?-carrageenan and locust bean gum gels
- 1998
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 34:4, s. 365-375
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Tidskriftsartikel (refereegranskat)abstract
- The viscoelastic and microstructural influences of 0.1-0.6% locust bean gum on 0.5 or 1.0% ?-carrageenan gels, in different ionic environments, have been studied using small deformation oscillatory measurements and transmission electron microscopy (TEM). The results from the rheological measurements showed synergistic effects in the storage modulus, G?, as locust bean gum, of two different mannose to galactose ratios (3 and 5), was mixed with ion-exchanged Na-and Ca-?-carrageenan, in 0.25 M NaCl and 0.030 M CaCl2, respectively. The increase in G? was dependent on the mannose to galactose ratio, polymer concentrations, and ionic environment. At the supermolecular level, the microstructure of dilute samples has been visualised using low angle rotary metal shadowing for TEM. In the presence of sodium and calcium ions, the self-association of ?-carrageenan helices is moderate to low. Locust bean gum did not influence the supermolecular structure of ?-carrageenan to any large extent. The microstructure of the gels at the network level was studied using plastic embedding and thin sectioning for TEM. In both sodium and calcium ionic environments, the mixed gels showed a more homogeneous and connective network structure. © 1998 Elsevier Science Ltd. All rights reserved.
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| 4. |
- Rindlav-Westling, A., et al.
(författare)
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Structure, mechanical and barrier properties of amylose and amylopectin films
- 1998
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 36:42038, s. 217-224
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Tidskriftsartikel (refereegranskat)abstract
- The effect of film formation conditions on structure, mechanical properties and barrier properties of amylose and amylopectin films was studied. The films were prepared by solution-gel-casting of amylose and amylopectin from potato, with or without the addition of glycerol as plasticizer. Transmission electron micrographs showed that the network structure characteristic for the amylose gel was also found in the film state. The amylose films without glycerol plasticization exhibited a relatively high degree of B-type crystallinity, as revealed by wide-angle X-ray diffraction, whereas the unplasticized amylopectin films were amorphous. Although the addition of glycerol did not affect the crystallinity of the amylose films, glycerol-plasticized amylopectin formed B-type crystallinity, and the degree of crystallinity was dependent on the air humidity during film formation. The degree of crystallinity affected the mechanical properties of the amylopectin films, whereas the mechanical properties of the amylose films were influenced by the network microstructure. Oxygen and water vapour permeabilities were dependent neither on the degree of crystallinity in the films nor on the network structure. © 1998 Elsevier Science Ltd. All rights reserved.
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