| 1. |
- Abdel Hady, Ahmed Wagih Abdallah, 1990, et al.
(författare)
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In situ microstructural evolution of spruce wood during soda pulping using synchrotron X-ray tomography
- 2022
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 76:7, s. 611-621
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Tidskriftsartikel (refereegranskat)abstract
- A new laboratory reactor to perform in situ studies of structural changes in wood during soda pulping using synchrotron X-ray tomography is presented. The reactor is of recirculation type to provide stable reaction conditions and mimic the industrial situation. Experiments have been performed using this reactor in situ at a synchrotron microtomography beamline to provide sequences of 3D images from which measurement of wood cell wall thickness have been possible for the first time. The results showed that the cell wall thickness increased significantly in the early stage of pulping (<10 min), which is due to the transportation of cooking chemicals through the tracheids, resin channels and pits into the cell wall, which is swollen with the increased pH. Subsequently, the cell wall thickness reduces over the processing time up to 60 min with a high rate, which is inferred to be due to the dissolution and transport of lignin and hemicellulose from the secondary walls, allowing for better transportation of active chemicals deep through the cell wall layers. After 60 min processing, the cell wall thickness reduction rate reduced, as dissolution of lignin and hemicelluloses from the cell walls ceased, while the remaining dissolution occurs mainly at the middle lamella.
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| 2. |
- Abdel Hady, Ahmed Wagih Abdallah, 1990, et al.
(författare)
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Micro/nano-structural evolution in spruce wood during soda pulping
- 2021
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 75:8, s. 754-764
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Tidskriftsartikel (refereegranskat)abstract
- Alkaline delignification of wood tissue is the core of the global pulping technology and the most prominent large-scale separation of the main wood components. This work aims at improved understanding of the interplay between the topochemistry of alkaline pulping and the associated morphological changes. Morphology and chemical structure of partially soda-delignified wood chips were studied combining X-ray tomography (XRT), X-ray diffraction analysis and compositional characterization (lignin and carbohydrate content). The XRT studies of wet samples (providing 3D structural information without interfering drying effects), allowed observation of the cell wall separation as an increasing amount of lignin was removed with the increasing pulping time. Comparison between the microstructure of the surface and the central parts of the treated chips showed a more delignified microstructure at the surface, which highlights the dependence of the delignification process on the mass transport (hydroxide ions and lignin fragments) through the wood tissue. The crystallite size of cellulose increased in the <200> crystal planes during the early stage of pulping while there was little effect on the <110> plane.
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| 3. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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A novel cold biorefinery approach for isolation of high quality fish oil in parallel with gel-forming proteins
- 2020
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 332
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Tidskriftsartikel (refereegranskat)abstract
- The pH-shift process for isolation of gel-forming proteins from fish processing by-products was extended to allow parallel isolation of fish oil. Subjecting the floating emulsion layer formed during pH-shift processing of salmon by-products to pH-adjustment or freeze/thawing efficiently released the emulsified oil at 4 °C. However, for herring by-products higher temperature (10 °C) and a combination of the emulsion-breaking techniques was required for efficient oil release. Oil recovery yield using the adjusted pH-shift process was lower than with classic heat-induced oil isolation (90 °C/20 min), but pH-shift-produced oils had higher amounts of n-3 polyunsaturated fatty acids (n-3 PUFA). Also, alkaline pH-shift processing produced oils with remarkably less oxidation products and free fatty acids compared with acid pH-shift process or heat-induced isolation. Extending the pH-shift process with emulsion breaking techniques can thus be a promising biorefinery approach for parallel cold production of high-quality fish oil and gel-forming proteins from fish by-products.
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| 4. |
- Abdollahi, Mehdi, 1985
(författare)
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Comparing physico-mechanical and thermal properties of alginate nanocomposite films reinforced with organic and/or inorganic nanofillers
- 2013
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 32:2, s. 416-424
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Tidskriftsartikel (refereegranskat)abstract
- Montmorillonite (MMT) and cellulose nanoparticles (CNP) were added to alginate biopolymer to compare the properties of bionanocomposites reinforced with different organic and inorganic nanofillers in various loading contents (1, 3, and 5 wt%). Both MMT and CNP decreased the water solubility (WS) of the films. However, at all filler contents the WS of the alginate/MMT (84–61%) nanocomposites was significantly (P < 0.05) lower than that of alginate/CNP films (95–77%). Surface hydrophobicity of the nanocomposites showed a great improvement (83%) with crystalline hydrophobic CNP addition, while MMT made films' surface more hydrophilic. The addition of both nanoreinforcements similarly caused a reduction in the water vapor permeability of the alginate-based nanocomposites. Due to the similar polysaccharide structures and good interfacial interactions, the TS and E of the nanocomposite films improved with an increase in CNP content and reached a maximum at the highest loading level (5 wt%). However, when the content of MMT went beyond 1 wt% nanocomposites, a decrease in the TS was observed. Finally, these results propose that organic CNP more than ability to make a fully renewable and natural nanocomposites may also introduce some other advantages compared to inorganic nanoclay fillers when added to carbohydrate biopolymers.
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| 5. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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Dynamic rheological, microstructural and physicochemical properties of blend fish protein recovered from kilka (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix) by the pH-shift process or washing-based technology
- 2017
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 229, s. 695-709
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to evaluate how blending pH-shift produced protein isolates from gutted kilka (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix) affected dynamic rheological and chemical properties of the proteins as well as microstructural and physico-mechanical properties of produced gels. Studied variables were protein solubilization pH (acid vs. alkaline) and blending step (before or after protein precipitation). Comparisons were made with conventionally washed minces from kilka and silver carp fillets; either alone or after blending. Rheological studies revealed that blending alkali-produced protein isolates before precipitation resulted in rapid increase of G′ reflecting the formation of intermolecular protein-protein interactions with higher rate. Furthermore, blending of alkali-produced protein isolates and washed minces, respectively, of kilka and silver carp improved physico-mechanical properties of the resultant gels compared to pure kilka proteins. However, the pH-shift method showed higher efficacy in development of blend surimi at the same blending ratio compared to the conventional washing.
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| 6. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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Effect of stabilization method and freeze/thaw-aided precipitation on structural and functional properties of proteins recovered from brown seaweed (Saccharina latissima)
- 2019
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 96, s. 140-150
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Tidskriftsartikel (refereegranskat)abstract
- - Structural, functional and nutritional properties of protein recovered from brown seaweed, S. latissima with alkaline solubilization/isoelectric precipitation as a function of different post-harvest stabilization methods were studied. The latter included freezing at −20 °C/-80 °C, oven-drying, sun-drying, freeze-drying and ensilaging. Also, the efficacy of freeze/thaw-aided precipitation (F/T) in improving protein recovery of the process was evaluated. The freeze-dried, oven-dried, and −20 °C frozen seaweeds resulted in significantly higher protein yield than the −80°C-frozen, sun-dried and ensiled biomasses. F/T increased protein precipitation and doubled total protein yield. Sun-drying and −20°C-freezing caused extensive protein degradation as revealed by SDS-PAGE and HP-SEC, while oven-drying altered the seaweed protein structure with less α-helices. Functional properties of the seaweed proteins were remarkably affected by stabilization condition and F/T, but nutritional value of the proteins was only dependent on stabilization method. Thus, to efficiently recover seaweed proteins, its post-harvest stabilization condition must be carefully chosen based on the final application of the proteins. © 2019 The Authors
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| 7. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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Minimizing lipid oxidation during pH-shift processing of fish by-products by cross-processing with lingonberry press cake, shrimp shells or brown seaweed
- 2020
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 327
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Tidskriftsartikel (refereegranskat)abstract
- The potential of cross-processing herring or salmon by-products with brown seaweed, shrimp peeling by-products and lingonberry press cake (called “helpers”) to minimize lipid oxidation during acid/alkaline pH-shift protein isolation was evaluated. Lingonberry press cake remarkably reduced levels of lipid hydroperoxides, malondialdehyde (MDA) and 4-hydroxy-trans2-hexenal (HHE) in both herring and salmon protein isolates (PI) while seaweed and shrimp by-product mitigated generation of MDA and HHE in herring PI. The salmon PI, however, by itself had very low oxidation levels. Cross-processing reduced protein yield compared with the classical pH-shift process by diminishing protein solubility, but still, the alkaline process version was promising. The color of the PIs varied greatly between different process combinations, reflecting partitioning of natural pigments into isolates. Altogether, cross-processing seems a promising tool for inhibition of lipid oxidation during pH-shift processing of sensitive fish by-products, with the alkaline version and lingonberry press cake being closest at hand for further studies.
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| 8. |
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| 9. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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Tuning the pH-shift protein-isolation method for maximum hemoglobin-removal from blood rich fish muscle
- 2016
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 212, s. 213-224
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Tidskriftsartikel (refereegranskat)abstract
- A main challenge preventing optimal use of protein isolated from unconventional raw materials (e.g., small pelagic fish and fish by-products) using the pH-shift method is the difficulty to remove enough heme-pigments. Here, the distribution of hemoglobin (Hb) in the different fractions formed during pH-shift processing was studied using Hb-fortified cod mince. Process modifications, additives and prewashing were then investigated to further facilitate Hb-removal. The alkaline pH-shift process version could remove considerably more Hb (77%) compared to the acidic version (37%) when proteins were precipitated at pH 5.5; most Hb was removed during dewatering. Protein precipitation at pH 6.5 improved total Hb removal up to 91% and 74% during alkaline and acid processing, respectively. Adding phytic acid to the first supernatant of the alkaline process version yielded 93% Hb removal. Combining one prewash with phytic acid at pH 5.5 followed by alkaline/acid pH-shift processing increased Hb removal up to 96/92%.
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| 10. |
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