| 1. |
- Altskär, Annika, et al.
(författare)
-
Some effects of processing on the molecular structure and morphology of thermoplastic starch
- 2008
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 71:4, s. 591-597
-
Tidskriftsartikel (refereegranskat)abstract
- Hydroxypropylated and oxidised potato starch (HONPS) was used together with glycerol and water to produce thermoplastic starch. The amount of glycerol was kept constant at 22 parts by weight per 100 parts of dry starch. The thermoplastic starch was converted into films/sheets using three different processing techniques; casting, compression moulding and film blowing. The last two methods represent typical thermoplastic conversion techniques requiring elevated processing temperatures. By means of size-exclusion chromatography, it was found that compression moulding and film blowing led to some degradation of high-molecular weight amylopectin as well as of high-molecular weight amylose-like molecules. The degradation was significantly less pronounced for the cast films. The morphology of the specimens was quite complex and phase separations on different levels were identified. In the cast films and, to a lesser extent, in the compression-moulded specimens, a fine network structure could be distinguished. Such a structure could however not be ascertained in the film-blown material and this is discussed in terms of the thermo-mechanical treatment of the starch materials. © 2007 Elsevier Ltd. All rights reserved.
|
|
| 2. |
- Bertoft, Eric, et al.
(författare)
-
Building block organisation of clusters in amylopectin from different structural types
- 2012
-
Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 50, s. 1212-1223
-
Tidskriftsartikel (refereegranskat)abstract
- Clusters of chains consisting of tightly branched units of building blocks were isolated from 10 amylopectin samples possessing the 4 types of amylopectin with different internal unit chain profiles previously described. It was shown that clusters in types 1 and 2 amylopectins are larger than in types 3 and 4, but the average cluster size did not correspond to the ratio of short to long chains of the amylopectins. The size-distribution of the building blocks, having one or several branches, possessed generally only small differences between samples. However, the length of the interblock segments followed the type of amylopectin structure, so that type 1 amylopectins had shortest and type 4 the longest segments. The chains in the clusters were divided into characteristic groups probably being involved in the interconnection of two, three, and four - or more - building blocks. Long chains were typically found in high amounts in clusters from type 4 amylopectins, however, all cluster samples contained long chains. The results are discussed in terms of the building block structure of amylopectin, in which the blocks together with the interblock segments participate in a branched backbone building up the amorphous lamellae inside growth rings of the starch granules. In such a model, amylopectins with proportionally less long chains (types 1 and 2) possess a more extensively branched backbone compared to those with more long chains (types 3 and 4). (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Eriksson, Estelle, et al.
(författare)
-
Evaluation of the physical and sensory characteristics of bread produced from three varieties of cassava and wheat composite flours
- 2014
-
Ingår i: Food and Public Health. - 2162-9412 .- 2162-8440. ; 4, s. 214-222
-
Tidskriftsartikel (refereegranskat)abstract
- This study determines the most suitable cassava variety and an acceptable maximum substitution level of wheat flour with cassava flour for bread production in terms of baking and organoleptic characteristics using three varieties of cassava. High Quality Cassava Flour produced from three cassava varieties (Afisiafi, Bankye hemmaa and Doku duade) was used together with wheat in composite at 10%, 20% and 30% substitution levels. Bread samples were baked from the resulting composites and examined for its specific volume, density and hardness. The products were also subjected to sensory analysis for appearance, taste, texture and overall acceptability by a semi-trained panel of consumers. Increasing proportion of cassava flour in the composite bread reduced bread specific volume and increased density and hardness. Increasing the content of cassava in the composite resulted in bread that was less springy and difficult to chew. Springiness of bread substituted with 10% and 20% cassava flour compared well with the control, while those with 30% cassava were significantly less springy than the control. A substitution level of 10% Afisiafi and 20 % Bankye hemmaa cassava flour in composite bread on overall acceptable was similar to 100% wheat bread and therefore has the most suitable potential to replace part of wheat flour in bakery products.
|
|
| 6. |
- Eriksson, Estelle, et al.
(författare)
-
Physicochemical, functional and pasting characteristics of three varieties of cassava in wheat composite flours
- 2014
-
Ingår i: British Journal of Applied Science and Technology. - 2231-0843. ; 4, s. 1609-1621
-
Tidskriftsartikel (refereegranskat)abstract
- Aims: The aim of this study was to examine the physicochemical and functional properties of cassava flour and in composite with wheat flour for bakery products. Study Design: A 3 x 3 factorial design of High Quality Cassava Flour and levels of inclusion in wheat flour were designed for the studies. Place and Duration of Study: Food Processing and Engineering Division of the CSIR-Food Research Institute, Accra and Department of Food Science, BioCenter, Swedish University of Agricultural Sciences, Uppsala, Sweden between January, 2012 and January 2013. Methodology: High quality cassava flour was processed from three cassava varieties asAfisiafi, Bankye hemmaaandDoku duade,formulated into composite flours at 10, 20 and 30% inclusion levels with wheat flour. The Physicochemical, functional and pasting properties of the flours were characterized. Results:Cassava flour appeared whiter and less yellowish had higher pH and lower water activity compared to wheat flour but moisture and starch content of the flours showed no significant differences (p>0.05). Flour from onlyDoku duadehad significantly igher amylose content than wheat flour. Generally, swelling power, solubility index, solubility volume and water binding capacity were greater in cassava flours than wheat flour. Increasing trend in these parameters was observed as cassava flour inclusion increased in the composite flour. Pasting performance in RVA showed a higher peak viscosity for cassava flour (3500–4089 cP) but lower paste stability and pasting temperature compared to wheat flour. Peak viscosity of the various composites were however comparable to that wheat flour but increasing cassava fraction resulted in early gelatinization and reduced retrogradation of the composite. Conclusion:The performance of cassava flour and its composite with wheat shows that it can be successfully adopted to replace a significant fraction of wheat flour.
|
|
| 7. |
|
|
| 8. |
- Kenward, Ben, et al.
(författare)
-
Saccadic reaction times in infants and adults : Spatiotemporal factors, gender, and interlaboratory variation.
- 2017
-
Ingår i: Developmental Psychology. - : American Psychological Association (APA). - 0012-1649 .- 1939-0599. ; 53:9, s. 1750-1764
-
Tidskriftsartikel (refereegranskat)abstract
- Saccade latency is widely used across infant psychology to investigate infants’ understanding of events. Interpreting particular latency values requires knowledge of standard saccadic RTs, but there is no consensus as to typical values. This study provides standard estimates of infants’ (n = 194, ages 9 to 15 months) saccadic RTs under a range of different spatiotemporal conditions. To investigate the reliability of such standard estimates, data is collected at 4 laboratories in 3 countries. Results indicate that reactions to the appearance of a new object are much faster than reactions to the deflection of a currently fixated moving object; upward saccades are slower than downward or horizontal saccades; reactions to more peripheral stimuli are much slower; and this slowdown is greater for boys than girls. There was little decrease in saccadic RTs between 9 and 15 months, indicating that the period of slow development which is protracted into adolescence begins in late infancy. Except for appearance and deflection differences, infant effects were weak or absent in adults (n = 40). Latency estimates and spatiotemporal effects on latency were generally consistent across laboratories, but a number of lab differences in factors such as individual variation were found. Some but not all differences were attributed to minor procedural differences, highlighting the importance of replication. Confidence intervals (95%) for infants’ median reaction latencies for appearance stimuli were 242 to 250 ms and for deflection stimuli 350 to 367 ms. (PsycINFO Database Record (c) 2017 APA, all rights reserved)
|
|
| 9. |
- Koch, Kristine, et al.
(författare)
-
Amylose and amylopectin molecular fractions and chain length distribution of amylopectin in 12 varieties of Ghanaian sweet potato (Ipomoea batatas) flours
- 2017
-
Ingår i: International Journal of Food Properties. - : Informa UK Limited. - 1094-2912 .- 1532-2386. ; 20, s. 3225-3233
-
Tidskriftsartikel (refereegranskat)abstract
- Sweet potato (Ipomoea batatas) is a commonly cultivated root crop in tropical and subtropical regions, including Ghana. Different varieties of sweet potato have been bred, in order to expand its utilisation within the food and industrial sector. This study analysed flours made from 12 recently developed Ghanaian sweet potato varieties in terms of their amylose and amylopectin molecular fractions and amylopectin chain length distribution. Starch content of the sweet potato flours ranged from 49 to 77 g/100 g dry matter, with 11 of the varieties containing above 60 g/100 g dry matter. An orange-fleshed variety, Apomuden, had the lowest amount of starch (48.9 g/100 g dry matter), while the cream-fleshed variety Histarch had the highest (77.3 g/100 g dry matter). The flours from the 12 sweet potato varieties had intermediate amounts of amylose, within the range 10-30 g/100 g dry matter, and showed typical molecular distribution according to size-exclusion chromatography (SEC). The fine structures of amylopectin, as revealed by anion-exchange chromatography, contained features common for starches of C-type X-ray pattern, but some structural differences were also observed.
|
|
| 10. |
- Koch, Kristine, et al.
(författare)
-
Material properties and molecular aspects of highly acetylated starch-based films
- 2014
-
Ingår i: Journal of Renewable Materials. - : Scrivener Publishing LLC. - 2164-6325 .- 2164-6341. ; 2:2, s. 134-144
-
Tidskriftsartikel (refereegranskat)abstract
- Properties of starch triacetate films from different botanical origins were evaluated. Tensile and barrier properties, glass transition temperatures and moisture uptake were measured, and the molecular structure was characterised. High-amylose starches were good film formers, normal potato starch formed continuous but brittle films and potato amylopectin formed very brittle films even after plasticisation. Barley amylopectin did not form continuous films. Different plasticisers were studied and diacetin was shown to perform better than the standard plasticiser triacetin. All films were water resistant, and the best films gave water vapour barriers in the range of films of polylactic acid, cellulose acetates and gluten. The inherent oxygen barrier of native starches was lost when the starches were highly acetylated. Starch triacetates are commonly dissolved in organic solvents such as chloroform. When testing different approaches to dissolve the starch triacetates it was found that acetic acid as well as acetylacetone were good solvents without imposing negative effects on material properties.
|
|
