| 1. |
- Ekberg, O., et al.
(författare)
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Effect of Barium Sulfate Contrast Medium on Rheology and Sensory Texture Attributes in a Model Food
- 2009
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 50:2, s. 131-138
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Tidskriftsartikel (refereegranskat)abstract
- Background: The swallowing process can be visualized using videoradiography, by mixing food with contrast medium, e.g., barium sulfate (BaSO4), making it radiopaque. The sensory properties of foods may be affected by adding this medium. Purpose: To evaluate if and to what extent sensory and rheological characteristics of mango puree were altered by adding barium sulfate to the food. Material and Methods: This study evaluated four food samples based on mango puree, with no or added barium sulfate contrast medium (0%, 12.5%, 25.0%, and 37.5%), by a radiographic method, and measured sensory texture properties and rheological characteristics. The sensory evaluation was performed by an external trained panel using quantitative descriptive analysis. The ease of swallowing the foods was also evaluated. Results: The sensory texture properties of mango puree were significantly affected by the added barium in all evaluated attributes, as was the perception of particles. Moreover, ease of swallowing was significantly higher in the sample without added contrast medium. All samples decreased in extensional viscosity with increasing extension rate, i.e., all samples were tension thinning. Shear viscosity was not as dependent on the concentration of BaSO4 as extensional viscosity. Conclusion: Addition of barium sulfate to a model food of mango puree has a major impact on perceived sensory texture attributes as well as on rheological parameters.
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| 2. |
- Richardson, Gisela, et al.
(författare)
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The function of alpha-crystalline emulsifiers on expanding foam surfaces
- 2004
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 18:4, s. 655-663
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Tidskriftsartikel (refereegranskat)abstract
- The expanding capacity and the stabilizing function of an alpha-crystalline emulsifier on the bubble surfaces during and after expansion of a sugar foam were examined by volume measurements, confocal laser scanning microscopy (CLSM), freeze-etching and transmission electron microscopy (TEM) and oscillatory theological measurements. 0.2-10% (w/w) emulsifier, either a polyglycerol ester mixed with monoglycerides (PGE/MG) in alpha-gel form or sodium oleate in micellar form, was mixed into a 65% sucrose solution in a specially designed vessel at a pressure of 1-5 bar. The foam produced was expanded to ambient pressure before measurements were made. The total volume of the foam was shown to increase proportionally to the expansion with both emulsifiers. With PGE/MG, small bubbles were produced (1-4 mum). With oleate, the bubbles became much larger (5-25 mum) and more coalescence could be observed. The storage modulus of the foam was shown to depend on the bubble sizes, the volume fraction of air and also the emulsifier. The foam stabilized with PGE/MG was stiff at a high concentration of emulsifier, while the micelle forming emulsifier remained more liquid-like. A possible explanation was that the alpha-crystalline PGE/MG emulsifier formed aggregates and caused an attractive bridging interaction between the bubbles, which resulted in a higher storage modulus. The micellar oleate did not cause any bubble bridging. (C) 2003 Elsevier Ltd. All rights reserved.
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| 3. |
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| 4. |
- Andersson, Helene, 1983, et al.
(författare)
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Extensional flow, viscoelasticity and baking performance of gluten-free zein-starch doughs supplemented with hydrocolloids
- 2011
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 25:6, s. 1587-1595
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Tidskriftsartikel (refereegranskat)abstract
- Viscoelastic doughs of zein and starch were prepared at 40 degrees C, above the glass transition temperature of zein. The effects of hydrocolloid supplementation with hydroxypropyl methylcellulose (HPMC) or oat bran with a high content of beta-glucan (28%) were investigated by dynamic measurements in shear, confocal laser scanning microscopy (CLSM) and Hyperbolic Contraction Flow. Zein-starch dough without hydrocolloids exhibited rapid age-related stiffening, believed to be caused by cross-links between peptide chains. A prolonged softness was attributed to doughs containing hydrocolloids, with the oat bran exhibiting the most pronounced reduction in age-related stiffening. Moreover, CLSM-images of dough microstructure revealed that a finer fibre network may be formed by increased shearing through an addition of viscosity-increasing hydrocolloids, a reduction in water content in the dough or the use of appropriate mixing equipment. The Hyperbolic Contraction Flow measurements showed that doughs containing hydrocolloids had high extensional viscosities and strain hardening, suggesting appropriate rheological properties for bread making. Zein-starch dough without hydrocolloids showed poor bread making performance while hydrocolloid additions significantly improved bread volume and height. Although the hydrocolloid supplemented doughs had similar extensional rheological properties and microstructures, a fine crumb structure was attributed only to bread containing HPMC, marking the importance of surface active components in the liquid-gas interface of dough bubble walls. Zein could not mimic the properties of gluten on its own, but hydrocolloids did positively affect the structural and rheological properties of zein, which yielded dough similar to wheat dough and bread with increased volume.
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| 5. |
- Anker, M., et al.
(författare)
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Aging of whey protein films and the effect on mechanical and barrier properties
- 2001
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 49:2, s. 989-995
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Tidskriftsartikel (refereegranskat)abstract
- This work focuses on the aging of whey protein isolate (WPI) films plasticized with glycerol (G) and sorbitol (S). The films were cast from heated aqueous solutions at pH 7 and dried at 23 °C and 50% relative humidity (RH) for 16 h. They were stored in a climate room (23 °C, 50% RH) for 120 days, and the film properties were measured at regular intervals. The moisture content (MC) of the WPI/G films decreased from 22% (2 days) to 15% (45 days) and was thereafter constant at 15% (up to 120 days). This affected the mechanical properties and caused an increased stress at break (from 2.7 to 8.3 MPa), a decreased strain at break (from 33 to 4%), and an increased glass transition temperature (T g) (from -56 to -45 °C). The barrier properties were, however, unaffected, with constant water vapor permeability and a uniform film thickness. The MC of the WPI/S films was constant at ?9%, which gave no change in film properties.
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| 6. |
- Anker, M., et al.
(författare)
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Effects of pH and the gel state on the mechanical properties, moisture contents, and glass transition temperatures of whey protein films
- 1999
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 47:5, s. 1878-1886
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties, moisture contents (MC), and glass transition temperature (T(g)) of whey protein isolate (WPI) films were studied at various pH values using sorbitol (S) as a plasticizer. The films were cast from heated aqueous solutions and dried in a climate chamber at 23 °C and 50% relative humidity (RH) for 16 h. The critical gel concentrations (c(g)) for the cooled aqueous solutions were found to be 11.7, 12.1, and 11.3% (w/w) WPI for pH 7, 8, and 9, respectively. The cooling rate influenced the c(g), in that a lower amount of WPI was needed for gelation when a slower cooling rate was applied. Both cooling rates used in this study showed a maximum in the c(g) at pH 8. The influence of the polymer network on the film properties was elucidated by varying the concentration of WPI over and under the c(g). Strain at break (?(b)) showed a maximum at the c(g) for all pH values, thus implying that the most favorable structure regarding the ability of the films to stretch is formed at this concentration. Young's modulus (E) and stress at break (?(b)) showed a maximum at c(g) for pH 7 and 8. The MC and ?(b) increased when pH increased from 7 to 9, whereas T(g) decreased. Hence, T(g) values were -17, -18, and -21 °C for pH 7, 8, and 9, respectively. E and ?(b) decreased and ?(b) and thickness increased when the surrounding RH increased. The thickness of the WPI films also increased with the concentration of WPI.
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| 7. |
- Anker, M., et al.
(författare)
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Improved water vapor barrier of whey protein films by addition of an acetylated monoglyceride
- 2002
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Ingår i: Innovative Food Science & Emerging Technologies. - 1466-8564 .- 1878-5522. ; 3:1, s. 81-92
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to determine to what extent the water-vapor barrier of whey protein isolate (WPI) films could be improved by adding a lipid and make laminate and emulsion films. The laminate whey protein-lipid film decreased the water vapor permeability (WVP) 70 times compared with the WPI film. The WVP of the emulsion films was half the value of the WPI film and was not affected by changes in lipid concentration, whereas an increased homogenization led to a slight reduction in WVP. The mechanical properties showed that the lipid functioned as an apparent plasticizer by enhancing the fracture properties of the emulsion films. This effect increased with homogenization. The maximum strain at break was 117% compared with 50% for the less-homogenized emulsion films and 20% for the pure WPI films. Phase-separated emulsion films were produced with a concentration gradient of fat through the films, but pure bilayer films were not formed. © 2002 Elsevier Science Ltd. All rights reserved.
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| 8. |
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| 9. |
- Anker, M., et al.
(författare)
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Mechanical Properties, Water Vapor Permeability, and Moisture Contents of ?-Lactoglobulin and Whey Protein Films Using Multivariate Analysis
- 1998
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Ingår i: Journal of Agricultural and Food Chemistry. - 0021-8561 .- 1520-5118. ; 46:5, s. 1820-1829
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical and barrier properties of ?-lactoglobulin (?-Lg) and whey protein isolate (WPI) films were studied using sorbitol (S) as a plasticizer. The films were cast from heated aqueous solutions and dried in a climate chamber at 23 °C and 50% relative humidity for 16 h. The multivariate analysis used has proved to be a valuable tool for evaluating and quantifying the influences of the variables in the specified experimental domain. Two identical factorial designs were applied to evaluate the influence of the concentration of ?-Lg and WPI, the concentration of S, and the pH. The two materials, ?-Lg and WPI, show similar results, which can be attributed to the dominating protein ?-lactoglobulin. At pH 9, Young's modulus and stress at break are not affected when the concentration of ?-Lg, WPI, or S varies. At pH 7 and 8, Young's modulus and stress at break increase when the concentration of ?-Lg and WPI increases, and they decrease when the concentration of S increases. Strain at break increases when pH increases from 7 to 9, a more pronounced effect being observed for the WPI films. Water vapor permeability (WVP) decreases and increases for pH 7 and 9, respectively, as the concentration of ?-Lg and WPI increases. This contrast in behavior at different pH values is probably due to a structural difference that occurs above pH 8. Moisture content and WVP increase when S increases. Here a clear distinction can be observed between the two film materials: the ?-Lg films show higher values for both moisture content and WVP measurements.
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| 10. |
- Anker, M., et al.
(författare)
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Relationship between the microstructure and the mechanical and barrier properties of whey protein films
- 2000
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 48:9, s. 3806-3816
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Tidskriftsartikel (refereegranskat)abstract
- This work was focused on the relationship between the microstructure and the mechanical and barrier properties of whey protein isolate (WPI) films. Sorbitol (S) and glycerol (G) were used as plasticizers and the pH was varied between 7 and 9. The films were cast from heated aqueous solutions and dried in a climate room at 23 °C and 50% relative humidity for 16 h. The microstructure of the films was found to be dependent on the concentration, the plasticizers, and the pH. When the concentration increased, a more aggregated structure was formed, with a denser protein network and larger pores. This resulted in increased water vapor permeability (WVP) and decreased oxygen permeability (OP). When G was used as a plasticizer instead of S, the microstructure was different, and the moisture content and WVP approximately doubled. When the pH increased from 7 to 9, a denser protein structure was formed, the strain at break increased, and the OP decreased.
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