| 1. |
- Fernandez, Celine, et al.
(författare)
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Size, structure and scaling relationships in glycogen from various sources investigated with asymmetrical flow field-flow fractionation and 1H NMR
- 2011
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 1879-0003 .- 0141-8130. ; 49:4, s. 458-465
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate the size, structure and scaling relationships in glycogen isolated from five different animal sources. For this purpose a versatile fractionation technique, asymmetrical flow field-flow fractionation (AsFlFFF), coupled to multi-angle light scattering, is utilized. For determination of the average degree of branching 1H NMR is utilized. The results give a detailed insight into the physico-chemical properties of glycogen over the whole size distribution. The results show that glycogen is a hyper branched macromolecule with wide size distributions, and in some samples two major populations are clearly observed which most likely correspond to β- and α-particles of glycogen. The results also illustrates that glycogen is a polysaccharide showing rather diverse conformational properties, over the size distribution, depending on its origin and the extraction procedure. The ratio between root-mean-square radius and hydrodynamic radius varies depending of both sample origin the molar mass of the macromolecules, reflecting differences in conformation and scaling within the size distribution. Thus, a priori assumptions regarding the rrms/rh are difficult to make and rrms/rh based on average properties give an incomplete description of the properties. Furthermore, the results display the strength of the apparent density (as obtained from AsFlFFF-MALS-RI) as a characterization parameter for scaling in disperse macromolecules. © 2011 Elsevier B.V.
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| 2. |
- Mérida-López, Jenny, et al.
(författare)
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Comparison of the Chemical Composition of Six Canihua (Chenopodium pallidicaule) Cultivars Associated with Growth Habits and after Dehulling
- 2023
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Ingår i: Foods. - 2304-8158. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- The canihua (Chenopodium pallidicaule) is a native Andean crop that stands out for its high content of protein, fiber, and minerals and that has a good fatty acid profile. We studied six canihuas cultivars, which were compared according to their proximate, mineral, and fatty acid composition. Based on the form of stems, termed growth habit, they belonged to two groups: decumbent (Lasta Rosada, Illimani, Kullaca, and Cañawiri) and ascending (Saigua L24 and Saigua L25). Dehulling is an important process applied to this grain. However, there is no information about how it affects the chemical composition of the canihua. Dehulling resulted in two levels, whole and dehulled canihua. The highest protein and ash contents were in whole Saigua L25 (19.6 and 5.12 g/100 g, respectively), and the highest fat content was found in dehulled Saigua L25, while the whole grains of Saigua L24 presented the highest fiber content (12.5 g/100 g). Dehulling mainly affected the macro-minerals content, while micro-minerals were only slightly linked to the dehulling. The growth habit influenced the C18:1 and C18:3 contents. In conclusion, the canihua had a nutritional composition influenced by each variety, strongly influenced by dehulling, and to a lesser extent by growth habit.
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| 3. |
- Pérez, Daysi, et al.
(författare)
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Enzymatic hydrolysis of Canna indica, Manihot esculenta and Xanthosoma sagittifolium native starches below the gelatinization temperature
- 2013
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Ingår i: Stärke. - : Wiley. - 0038-9056 .- 1521-379X. ; 65:1-2, s. 151-161
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Tidskriftsartikel (refereegranskat)abstract
- The susceptibility to enzymatic hydrolysis of starch extracted from raw roots of Canna indica, Manihot esculenta and Xanthosoma sagittifolium, grown in Bolivia, were studied below the gelatinization temperature. The granule size and amylose content were as followed: C. indica>M. esculenta>X. sagittifolium. The hydrolysis showed a rapid rate at the initial stage, followed by a progressive decrease thereafter. At 30, 40 and 50 degrees C, during the initial stage, the rate of hydrolysis was observed to be influenced by the size of the granules, being the highest for the small sized granules X. sagittifolium, followed by the medium sized granules M. esculenta and the lowest rate was for the large sized granules C. indica starch. During the slow phase, A-type M. esculenta and B-type C. indica showed higher hydrolysis rates than A-type X. sagittifolium. At 60 degrees C, a positive correlation was found between the amylose content and the rate of hydrolysis among the starches. Microscopic observations showed a pattern of attack by the enzyme towards C. indica starch granules, suggesting that high amylose content is concentrated around the hilum.
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| 4. |
- Perez, Sander, et al.
(författare)
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Water and Thermal Properties Characterized in Phases of Wheat Flour Dough during Thawing and Baking Conditions
- 2019
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Ingår i: Advances in Food Science and Engineering. - : Isaac Scientific Publishing Co., Ltd.. - 2520-7091 .- 2520-7105. ; 3:3, s. 48-62
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Tidskriftsartikel (refereegranskat)abstract
- Phase separation of dough is based on the thermodynamic incompatibility of its components. The studies on phase-separated systems allow to model, understand, and develop foods. Model dough systems made with water and wheat flour were disassembled into their main structural phases, i.e. liquid, gel, gluten and starch phases, by ultracentrifugation, and further characterized with differential scanning calorimetry (DSC) and microscopy. The study of phase separation, water properties and thermal transitions in phases showed that wheat flour doughs are mainly characterized by the volume fractions of liquid, gel and gluten. The different samples of flours were highly affected by flour combinations. The freezable water (FW) of each separated phase influenced the water properties of the whole dough. The FW is further related to starch thermal behaviour of dough systems at baking temperatures. The methods used here were therefore found relevant from a baking perspective for initial characterizing of flours and dough.
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| 5. |
- Rojas, Carola, et al.
(författare)
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Macromolecular geometries determined with field-flow fractionation and their impact on the overlap concentration.
- 2008
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 9:6, s. 1684-1690
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we aim to understand the size/conformation relationship in waxy barley starch, a polydisperse and ultrahigh molar mass biomacromolecule. Characterizations are performed with asymmetrical flow field-flow fractionation (AsFlFFF). Furthermore, we study the effect of homogenization on the molar mass, rms radius (r rms) and hydrodynamic radius (r h). For the untreated sample, the macromolecules are elongated objects with low apparent density. As a result of homogenization, molar mass, and r rms decrease, while r h remains unaffected. The process also induces an increase, and scaling with size, of apparent density as well as changes in conformation, represented qualitatively by r rms/ r h. Finally, results from AsFlFFF are compared with viscosimetry and discussed in terms of concentration and close-packing in relation to macromolecular shape and conformation. Hence, the results show that AsFlFFF and our novel methodology enable the determination of several physical properties with high relevance for the solution behavior of polydisperse macromolecules.
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| 6. |
- Rojas, Carola
(författare)
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Processing of raw Cassava (Manihot esculenta) - Experiments and Modelling.
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the present thesis was to understand how the quality and performance of dried cassava products could be developed by drying and other processing steps. This goal was achieved in several stages. First, a survey of the composition of six cassava varieties from Bolivia, was performed, which resulted in the report of chemical and mineral compositions of the tubers. The mineral compositions of the tubers were compared to the elemental composition of the soil in order to identify depleted and enriched elements. In a second step, an enzymatic assay for the determination of lower sugars in cassava was developed. This technique rendered it possible to measure the content of free glucose, maltose and sucrose in six varieties of cassava. The third step implied the development of a process for partial hydrolysis of non-gelatinized cassava starch. In this study, the kinetics of the enzymatic hydrolysis of raw cassava starch were described as a heterogeneous system, and the investigation involved leaching of amylose during starch granule swelling, and morphological characterizations of starch granules using SEM as well as light microscopy. Results included a model describing the kinetics of the enzymatic hydrolysis and which assumed a blocklet structure of the starch granule and reveals that the enzymatic attack occurs mainly at the interior starch-water interface of the granule. Fourth, a model describing the kinetics of the drying of cassava starch was put forward. From this investigation, a quasi steady state model was developed based on heat and mass transfer. Finally, the impact of high pressure homogenization of dissolved starch was studied, which involved the degradation and conformational changes of starch as caused by the process. The characterization was performed with AsFlFFF with MALS and RI detection. Upon high pressure homogenization, the molar mass, mean square radius and hydrodynamic radius were found to decrease. The process also induced an increase and scaling with size in the apparent density of the macromolecules in addition to alterations in the molecular conformation. Furthermore, homogenization caused an increase in the overlap concentration. During the investigations constituting this thesis, native cassava of Bolivia was discovered to be a fairly tasteless starch-rich product with a low degree of sweetness. In order to be used as a base for drinks, as is the case for chive, an interesting concept could be to partly hydrolyze the starch. In granular form its kinetics was described. Moreover, granular starch can be efficiently dried. The hydrolysis may restrict the viscosity-generating properties of the starch, and a critical parameter is the overlap concentration. The present study has shown that this parameter is not very dependent on the molar weight of the starch.
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