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| 2. |
- Bayod, Elena, et al.
(författare)
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Low shear rheology of concentrated tomato products. Effect of particle size and time
- 2007
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Ingår i: Food Biophysics. - : Springer Science and Business Media LLC. - 1557-1866 .- 1557-1858. ; 2:4, s. 146-157
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Tidskriftsartikel (refereegranskat)abstract
- Time-dependent rheological properties of three tomato paste suspensions in the concentration range of 200-1,000 g paste/kg suspension have been investigated by using the vane geometry at shear rates gamma < 10 s(-1). Creep tests were conducted to analyze the influence of the level of stress on the rheological behavior of the samples before and after homogenization. The experimental results indicate that the suspensions exhibit an elastic behavior at long times and relatively low stresses, which proves that this type of material can be characterized by a yield stress (sigma(y)). Applying stresses just beyond the yield stress, an initial rheopectic behavior appeared. This increase in viscosity at low deformations was markedly larger after homogenization, and this difference was attributed to changes in the aspect ratio, shape, and orientation of the particles induced by homogenization. These structural changes were also reflected in the transient viscosity when the samples were subjected to larger stresses (sigma >>sigma y): before homogenization the suspensions exhibited a steady-state viscosity at large deformations, whereas after homogenization, the transient viscosity continuously decreased. That behavior was attributed to flocculation of the particles.
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| 3. |
- Börjesson, Erik, et al.
(författare)
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Entrapment of air during imbibition of agglomerated powder beds
- 2017
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 201, s. 26-35
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Tidskriftsartikel (refereegranskat)abstract
- Complete wetting is crucial for efficient recombination of powders. On the powder bed scale, wetting is governed solely by capillary forces and the resistance to flow, i.e. spontaneous imbibition. Slow or incomplete imbibition of the powder bed may lead to gelling of the liquid front, which will stop the recombination process and cause the formation of lumps, which is usually undesirable. In this study, the spontaneous imbibition of powder beds consisting of spray-dried dairy powders with diverse morphologies has been investigated. Uniform radial spreading of the imbibition front was seen in all the beds, but a large amount of air was trapped in the inter-particle free space in the imbibed volume. A positive correlation was found between bed porosity and the fraction of air trapped in the bed after imbibition. Since the amount of trapped air was calculated as a fraction of the porosity of the dry bed, this relation was unexpected. The large fraction of air trapped in the bed and the uniform radial spreading of the imbibition front indicate considerable heterogeneity of bed on the microscopic scale, but a homogenous structure on the macroscopic scale. Possible explanations of the large fraction of trapped air are the presence of local dead-end structures in the bed and film flow of the imbibing liquid.
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| 4. |
- Börjesson, Erik, et al.
(författare)
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Evaluation of particle measures relevant for powder bed porosity-A study of spray dried dairy powders
- 2014
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Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910. ; 253, s. 453-463
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Tidskriftsartikel (refereegranskat)abstract
- The formation of lumps during large scale wetting of spray dried powders is a common problem in the industry. The result is a large energy demand if an efficient mixing is to be achieved at the industrial scale. If more knowledge regarding the phenomena governing lump formation is obtained, the unit operation could be optimized and made more efficient. As a part of increasing the understanding of lump formation, the wetting of the porous media that is a powder bed needs to be understood. This wetting relates to the structure and void space (porosity) of the powder bed, which is why a relation between powder bed porosity and readily obtainable powder particle morphology parameters is sought. In this study a thorough investigation of the morphology of five different spray dried milk powders, with arbitrary particle shapes, was performed using manual image analysis of scanning electron microscope (SEM) images as well as automated methods based on light scattering and projected image analysis. The results of the automated methods, when utilized on the complexly shaped samples, were validated by a comparison to the SEM image analysis. This enabled the development of a relation between powder morphology and powder bed porosity based on data from automated methods. The results indicate that automated methods based on light scattering underestimate the particle sizes of arbitrary shaped particles. Methods based on projected image analysis, however, show a better agreement with SEM image analysis. The developed relation between powder bed porosity and powder particle morphology is based on defining the bed as having either an "Agglomerates in fines", "Bicontinuous" or "Fines in agglomerates" structure. The structure of each powder is determined based on calculation of a "BedRatio" which is a function of the phi(agglomerate) and phi(fines) both shown to be readily obtainable by automated methods. The calculated porosities of the powders investigated in this study show a good agreement with experimental measurements and are considered to correspond well to earlier literature. It is, however, clear from the a experiments that care needs to be taken during bulk density measurement of spray dried powders so that no intra particle void space is taken into consideration in the calculations. (C) 2013 Elsevier B.V. All rights reserved.
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| 5. |
- Börjesson, Erik, et al.
(författare)
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The dissolution behavior of individual powder particles
- 2013
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Ingår i: Dairy Science & Technology. - : Springer Science and Business Media LLC. - 1958-5586 .- 1958-5594. ; 93:4-5, s. 357-371
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Tidskriftsartikel (refereegranskat)abstract
- The formation of lumps is a common problem during powder reconstitution in food industry. If more knowledge regarding the phenomena controlling the process could be obtained, the process of industrial powder recombination could be optimized. This demands investigation of the process at three different levels: the scale of individual powder particles, the scale of powder beds, and the scale of industrial recombination. If knowledge from all three scales could be combined, a model of the entire process could be constructed. In this study, we present a new flow-cell-based method for investigating the dissolution rate of individual powder particles in controlled liquid flow. The flow cell allows for alteration of the flow velocity and only subjects the investigated powder particles to mild stress before the analysis. The dissolution process in the cell is recorded, and data are obtained by image analysis. Sodium caseinate has been used as a model substance in these experiments. The results show that the particle dissolution rate is a function of the flow velocity of the liquid, and the results correspond to earlier established methods. The investigation of individual particles shows a variation in dissolution rate between particles resulting from the diverse particle morphology from an industrial batch of powder. The results indicate that the dissolution interface concentration of dissolving sodium caseinate particles corresponds well to the overlap concentration of the specie.
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| 6. |
- Castro, Alejandra, et al.
(författare)
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Dietary fiber, fructooligosaccharides, and physicochemical properties of homogenized aqueous suspensions of yacon (Smallanthus sonchifolius)
- 2013
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Ingår i: Food Research International. - : Elsevier BV. - 0963-9969. ; 50:1, s. 392-400
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Tidskriftsartikel (refereegranskat)abstract
- Yacon roots are a promising source of inulintype fructans (35 g/100 g dry matter) with a total amount of dietary fiber of about 45 g/100 g dry matter. The polydispersity of the particle size distribution of yacon aqueous suspension was reduced with increasing the degree of homogenization due to two phenomena: aggregation of particles, and disruption of large particles. Nonhomogenized yacon suspensions exhibited large cell clusters that were disrupted into small cell clusters, single cells, and aggregates. The most concentrated suspension exhibited mainly aggregates. The reducing effect of homogenization and the absence of a concentration effect on volume fraction were attributed to the dense packing of small particles and aggregates in between large particles thus allowing the water within the structure to be released. Yacon suspensions exhibited high elastic modulus (750 Pa) at low water insoluble solids content (0.9 % WIS). The results suggested that inulintype fructans contributed to the elastic properties of yacon suspensions. Yacon suspensions exhibited brittle flow behavior and they can be considered as semiconcentrated i.e. the yacon suspensions studied in this work represented a region immediately after the transition region where the rheological properties of yacon suspensions are dependent on concentration, particle interaction, and particle properties. Particle interactions seem to be of great importance as the elastic modulus (G’) reached 750 Pa at low water insoluble solids content (<1%).
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| 7. |
- Castro, Alejandra, et al.
(författare)
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Effect of heat tretment and homogenization on the rheological properties of aqueous parsnip suspensions
- 2013
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 117:3, s. 383-392
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Tidskriftsartikel (refereegranskat)abstract
- Parsnip (Pastinaca sativa) suspensions, at concentrations corresponding to a dilute and concentrated regime, were subjected to pasteurization, and heat treatments that favored beta-elimination reactions and pectin methyl esterase activity. The different heat treatments were combined with homogenization. Physicochemical properties such as content of insoluble/soluble material and insoluble/soluble pectin were measured together with particle and rheological properties. Pectin methyl esterase activity led to a high yield of insoluble material and insoluble pectin, whereas beta-elimination led to a high yield of soluble material and solubilized pectin. Homogenization after heat treatment resulted in increased solubilization of the pectin, especially after beta-elimination reactions. Parsnip suspensions subjected to pectin methyl esterase activity exhibited the highest elastic modulus most likely due to the cross-linked pectin conferring rigidity to the cell walls. The content of insoluble material and the particle properties such as size and rigidity are important factor for the rheological properties of concentrated parsnip suspensions.
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| 8. |
- Castro, Alejandra, et al.
(författare)
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Parsnip (Pastinaca sativa L.): Dietary fibre composition and physicochemical characterization of its homogenized suspensions
- 2012
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Ingår i: Food Research International. - : Elsevier BV. - 0963-9969. ; 48:2, s. 598-608
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Tidskriftsartikel (refereegranskat)abstract
- The dietary fibre composition in parsnip has been determined in the soluble and insoluble fraction, together with the physicochemical properties (morphology of particles, particle size distribution (PSD), volume fraction and rheological properties) of the parsnip suspensions at different paste concentration and degree of homogenization. The content of dietary fibre in parsnip was 30.4% of the dry matter, composed mainly by neutral sugars (18.4%), pectic substances (10.10%) and Klason lignin (1.92%). Homogenization affected the particle size distribution of parsnip suspension (p<0.001). resulting in smaller cell-clusters. By increasing the degree of homogenization, the area based diameter of large particles (d(32L)) and the volume percentage of large particles (vol(L)%) decreased, whereas the volume percentage of small particles (vol(S)%) increased. Concentration affected the rheological properties of parsnip suspensions (p<0.001). The volume fraction (phi) increased with paste concentration but was reduced with homogenization. By plotting the elastic modulus, G', as a function of volume fraction, phi, we showed the existence of a diluted and concentrated regime with a transition region at approximately phi = 19% for parsnip suspensions. Above the transition region, concentration of particles played an important role for the rheological properties. Based on the results achieved in this investigation we suggest that the gel network is mainly formed by the large particles, e.g. >100 mu m, and the smaller are preferably in the voids between the larger ones. (C) 2012 Elsevier Ltd. All rights reserved.
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| 9. |
- Castro-Alba, Vanesa, et al.
(författare)
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Effect of fermentation and dry roasting on the nutritional quality and sensory attributes of quinoa
- 2019
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Ingår i: Food Science and Nutrition. - : Wiley. - 2048-7177. ; 7:12, s. 3902-3911
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundQuinoa is a pseudocereal with relatively high content of proteins and minerals that also contains mineral inhibitors such as phytate. The aim of the present study was to evaluate lactic acid fermentation and dry roasting on the nutritional quality and sensory attributes of quinoa. Various processes were evaluated, and quinoa grains were dry-roasted, milled, and fermented, either with or without the addition of wheat phytase or activated quinoa phytase (added as back-slop starter), for 10 hr. In other processes, raw quinoa flour was fermented for 10 hr or 4 hr and dry-roasted. Hedonic sensory evaluation was then performed to evaluate the acceptability of the fermented flours prepared as porridges. ResultsThe combined dry roasting and fermentation processes significantly (p < .05) degraded phytate between 30% and 73% from initial content. The most effective process was fermentation of raw quinoa flour followed by dry roasting, which improved the estimated zinc and iron bioavailability. Particularly, estimated zinc bioavailability improved from low (Phy:Zn 25.4, PhyZn:Ca 295) to moderate (Phy:Zn 7.14, PhyZn:Ca 81.5). Phytate degradation was mainly attributed to the activation of endogenous phytase during fermentation. Dry roasting was effective in improving the sensory attributes of the fermented quinoa flour. Porridge made with raw quinoa flour fermented for 4 hr and dry-roasted was more favorable to overall acceptability than that which was fermented for 10 hr and dry-roasted. ConclusionFermentation of quinoa flour for 4 hr followed by dry roasting was successful in improving both nutritional and sensory attributes of the final product.
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| 10. |
- Chambal, Borges, et al.
(författare)
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Edible proteins from coconut milk press cake; one step alkaline extraction and characterization by electrophoresis and mass spectrometry
- 2012
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Ingår i: Food Research International. - : Elsevier BV. - 0963-9969. ; 47:2, s. 146-151
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Tidskriftsartikel (refereegranskat)abstract
- Coconut milk press cake, the spent endosperm left over after the extraction of coconut milk, was utilized to extract additional protein under alkaline conditions. The maximum protein yield was observed at 50 degrees C and pH 11 and corresponded to total endosperm protein yield of 71%, favourably comparable to yields of more complex extractions. The extract was characterized by amino acid analysis and 1D SDS-PAGE, 2D electrophoresis and MS MS spectroscopy. Coconut milk and insoluble milk sediment from the same individual nuts were also analyzed. The alkaline extract reproducibly differed from the other fractions and from those reported by others in amino acid content as seen in Principal Component Analysis, and had in particular higher threonine content The peptide found in the alkaline extract but with no counterpart in coconut milk or its sediment showed IP (approximate to 5) and mass (approximate to 40 kDa) and matched partially glutelin from oil palm. (c) 2011 Elsevier Ltd. All rights reserved.
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