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| 3. |
- Georgopoulos, Theofanis, et al.
(författare)
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A comparison of the rheological properties of wheat flour dough and its gluten prepared by ultracentrifugation
- 2004
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Ingår i: Food Hydrocolloids. - 0268-005X. ; 18:1, s. 143-151
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Tidskriftsartikel (refereegranskat)abstract
- Ultracentrifugation has been used as a tool for separating dough into different phases and as dough can be described as a bicontinuous system, gluten forms one phase, and starch another. The aim of this study is to investigate the possibility of using ultracentrifugation to extract gluten from dough. By using this method disadvantages such as excess washing, drying and reconstitution of dried gluten (involving a second mixing) were avoided. Gluten samples were obtained by this method (doughs differing in water content from 42.6 to 47.1%) and the rheological properties of dough and the corresponding gluten were studied in frequency sweep. The gluten coming from dough after ultracentrifugation had water contents in the range of 54.2–58.8%. An increase in water content reduced the storage modulus to a greater extent than the loss modulus for the studied dough. The gluten was not affected to the same extent by an increase in water content, as was the dough. The ratios of G′dough/G′gluten and G″dough/G″gluten approached the value of 1 when the amount of dough water increased. The slope of log G″ versus log for gluten (n″gluten) were always higher than n′gluten. For dough the slope of log G″ versus log (n″dough) were on the same level or higher than (n′dough). It was concluded that both the frequency dependency and the values of G′ and G″ were more or less independent of water content for gluten. On the contrary dough showed a strong dependency of water content in particular for the value of G′ and the frequency dependency of G′.
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- Ortega-Ojeda, Fernando, et al.
(författare)
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Gel formation in mixtures of amylose and high amylopectin potato starch
- 2004
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 57:1, s. 55-66
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Tidskriftsartikel (refereegranskat)abstract
- The influence of amylopectin (Ap) (in the form of high amylopectin potato starch, HAPP) on the rheological properties of its mixtures with amylose (Am) has been studied in small-deformation oscillatory rheometry during relatively long times (6 h). The absence of HAPP granule remnants in the samples has been considered important; therefore HAPP, Am, and HAPP-Am mixtures have been prepared at 140degreesC. A higher amount of HAPP in the HAPP-Am mixture resulted in a lower value of G' of the formed systems. This trend was stronger at 10 and 8%, than at 6% total polysaccharide concentration. The rheological properties of the mixtures with the lowest amount of Am resulted in a theological behaviour that was similar to that of HAPP at identical concentration. With increasing Am concentration in the Am-HAPP mixtures, the behaviour was comparable to pure Am. HAPP did not seem to increase the effective concentration of Am and act as a precipitator. The frequency dependence of G'(n') strongly drop with increasing Am concentration until a certain ratio of Am:HAPP was reached, approaching zero. This implied a drastic liquid-solid transition, which was clearer at higher total polysaccharide concentrations. The values of G' for pure Am increased more rapidly and at considerably lower concentrations than for pure HAPP. For HAPP the decrease in n' with increasing concentration was gradual, in three different stages. First a strong decrease in n' and W to a more or less constant value (similar to0.5) and then, at the highest concentration, n' decreased even further, and approached zero. For Am, the values of n' decreased abruptly from similar to1 to similar to0 with increasing concentration, which implies a distinct liquid to solid transition. (C) 2004 Elsevier Ltd. All rights reserved.
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| 5. |
- 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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| 6. |
- Waller, John, et al.
(författare)
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Knowledge of osteoporosis in a Swedish municipality : a prospective study
- 2002
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Ingår i: Preventive Medicine. - : Elsevier BV. - 0091-7435 .- 1096-0260. ; 34:4, s. 485-491
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Tidskriftsartikel (refereegranskat)abstract
- Background. As a part of the Vadstena Osteoporosis Prevention Project, the knowledge of osteoporosis was examined before the intervention program started, after 5 and 10 years.Methods. At baseline (in 1989) 15% of the population in two Swedish municipalities was randomly invited to the study. The participants in the study group were invited for examination by forearm bone densitometry and a questionnaire concerning lifestyle and risk factors for osteoporosis and also knowledge of osteoporosis, while the subjects in the control group were examined only by questionnaire. Follow-ups were made in 1994 and in 1999. Meanwhile education about osteoporosis was given to the study group, to the public, and to various professionals in the study community.Results. There was a difference in the level of knowledge between the groups prior to the intervention. The rate of increment did not differ significantly between the groups for the study period. Previous participants had 0.58 higher score than new participants in the study group in 1994 (P = 0.031) and 0.76 higher score in 1999 (P < 0.001) regarding the total number of correct answers. The women in the study group had 0.63 higher score than the men in 1994 (P = 0.016) and 1.03 higher score in 1999 (P < 0.001) regarding the total number of correct answers.Conclusion. There was no significant effect of a general intervention program concerning the knowledge of osteoporosis in participants in the intervention area compared to the control area.
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| 7. |
- Watanabe, A, et al.
(författare)
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Effect of physical state of nonpolar lipids on rheology and microstructure of gluten-starch and wheat flour doughs
- 2002
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Ingår i: Cereal Chemistry. - 0009-0352. ; 79:2, s. 203-209
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Tidskriftsartikel (refereegranskat)abstract
- To clarify the effects of solid fat and liquid oil on dough in more detail in a simpler system, gluten-starch doughs with different gluten contents were investigated. The results from rheological measurements indicate that dough with a higher starch content has less resistance to strain and dough with a lower starch content has a rubber-like structure. The effects of the physical state of nonpolar lipids such as fat and oil on gluten-starch doughs and wheat flour doughs were investigated using rheological measurements and scanning electron microscopy. Fat-containing dough had more gas cells and a very smooth gluten gel surface with few holes, which may provide higher tolerance to strain. Moreover, the fat seemed to uniformly distribute the gluten gel between the starch granules in the dough, which reduced the friction between starch granules and led to a lower storage modulus. A mechanism governing the effect of fats on loaf volume is proposed based on the phenomena observed in the fat-containing dough.
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