| 1. |
- Lindmark Månsson, Helena, et al.
(author)
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Two-dimensional gel electrophoresis of proteins and peptides in bovine milk
- 2005
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In: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 15:2, s. 111-121
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Journal article (peer-reviewed)abstract
- Proteins and peptides in bovine milk and colostrum were separated by two-dimensional gel electrophoresis (2-DE). The proteins were separated in the first dimension by isoelectric focusing in the pH ranges 4-7 and 6-11, and in the second dimension by sodium dodecyl sulphate polyacrylamide gel electrophoresis on 12.5% T homogeneous gels. The peptides were separated in the pH range 3-10 in the first dimension, while 15% T homogeneous gels were used in the second dimension. 2-DE evaluation of samples with various somatic cell counts showed an increased number of peptides with increased cell count. 2-DE analysis of samples heated at 65 and 85 degreesC for 30 min showed a decrease in the number of proteins and peptides with increased temperature. Colostrum exhibited a peptide pattern in which the intensity and number of spots decreased with time postpartum. These results show that 2-DE is a useful tool to detect variations of proteins and peptides in milk.
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| 2. |
- Marefati, Ali, et al.
(author)
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Fabrication of encapsulated oil powders from starch granule stabilized W/O/W Pickering emulsions by freeze-drying
- 2015
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In: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 51, s. 261-271
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Journal article (peer-reviewed)abstract
- The process stability of water-in-oil-in-water (W/O/W) double emulsions stabilized with food-grade OSA modified quinoa starch granules was investigated. The effect of oils with differing melting points, as well as the effect of in situ partial gelatinization of the granules, on stability of emulsions was also investigated. The physical stability and release of a tracer (carmine) from the internal aqueous phase of double emulsions were characterized after each process stage using particle size analysis, light microscopy and spectrophotometry. When liquid shea oil was used the particle sizes varied in mode of D[4,3] from 28 +/- 2 mu m for initial fresh double emulsions to 90 +/- 7 mu m for heat treated and 210 +/- 11 mu m for heat treated, freeze-dried and reconstituted emulsions. Non-heat treated emulsions collapsed on freeze-drying due to high susceptibility of liquid oil droplets towards destabilization, when the external aqueous phase is crystalized. When solid shea oil was used the mode of D[4,3] varied from 48 +/- 0 mu m in initial emulsions to 118 +/- 3 mu m for heat treated emulsions and the freeze-dried and reconstituted emulsions showed 62 +/- 3 mu m or 85 +/- 11 mu m for non-heat treated and heat treated samples respectively. Reconstituted freeze-dried emulsion retained the encapsulated marker to over 97%. Overall, application of oil phase solid at room temperature and in situ heat treatment had a positive impact on process stability towards freezing and freeze drying. The result of this study revealed the feasibility to develop food-grade oil filled powders from OSA modified starch Pickering emulsions with approximately 70 wt% oil content by freeze-drying. (C) 2015 Elsevier Ltd. All rights reserved.
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| 3. |
- Marefati, Ali, et al.
(author)
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Freezing and freeze-drying of Pickering emulsions stabilized by starch granules
- 2013
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In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 436, s. 512-520
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Journal article (peer-reviewed)abstract
- The aim of this study was to investigate the possibility to produce novel powder materials based on chemically modified starch granule stabilized Pickering oil-in-water (O/W) emulsions. This study also investigated the effect of partial starch gelatinization in situ, dispersed phase type (two oil types with different melting points), freezing method and thawing, and freeze-drying and rehydrating on the overall properties of the emulsions. The emulsions showed high freeze thaw stability. The results of this study demonstrated the feasibility of the production of oil containing hydrocolloid-based powders, through combination of heat treated or even non-heat treated starch Pickering emulsions and freeze-drying. The final powders comprised high weight percentage of oil (over 80%, w/w). Upon rehydration of powders, the starch stabilized oil drops were found to be only moderately affected by the process with some aggregation observed. (C) 2013 Elsevier B.V. All rights reserved.
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| 4. |
- Marku, Diana, et al.
(author)
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Characterization of starch Pickering emulsions for potential applications in topical formulations.
- 2012
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In: International Journal of Pharmaceutics. - : Elsevier BV. - 1873-3476 .- 0378-5173. ; 428:1-2, s. 1-7
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Journal article (peer-reviewed)abstract
- The aim of this work has been to characterize starch based Pickering emulsions as a first step to evaluate their possible use as vehicles for topical drug delivery. A minor phase study of emulsions with high oil content has been performed. Emulsion stability against coalescence over eight weeks and after mild centrifugation treatment has been studied. The particle size, rheological properties and in vitro skin penetration of emulsions containing three different oils (Miglyol, paraffin and sheanut oil) was investigated. It was shown that it is possible to produce oil in water starched stabilised Pickering emulsions with oil content as high as 56%. Furthermore, this emulsions show good stability during storage over eight weeks and towards mild centrifugation. The particle size of the systems are only dependent on the ratio between oil and starch and for liquid oils the type of oil do not affect the particle size. The type of oil also affects the cosmetic and rheological properties of the creams but did not affect the transdermal diffusion in in vitro tests. However, it seems as if the Pickering emulsions affected the transport over the skin, as the flux was twice that of what has been previously reported for solutions.
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| 5. |
- Matos, María, et al.
(author)
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Preparation and encapsulation properties of double Pickering emulsions stabilized by quinoa starch granules
- 2013
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In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 423, s. 147-153
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Journal article (peer-reviewed)abstract
- Double emulsions have potential applications in the food, cosmetic and pharmaceutical industries as vehicles for encapsulation and delivery of nutrients during food digestion or as drug release. The major drawback of this type of emulsions is that they are often difficult to stabilize. Particle stabilized emulsions, known as Pickering emulsions, show special features, such as being extremely stable with respect to coalescence. Starch granules have proved to be a suitable stabiliser for food grade Pickering emulsions. In this work, starch double W1/O/W2 Pickering emulsions were prepared and their encapsulation stability was studied as well as the impact of varying the lipophilic emulsifier (PGPR90) content and salt concentration in the W1 inner aqueous phase. Encapsulation properties were quantified by monitoring the release of a hydrophilic dye from the inner aqueous phase spectrophotometrically. Two double emulsion systems were studied, one with an inner aqueous phase with 0.1M NaCl and the other with 0.2M NaCl. The initial encapsulation efficiency was over 98.5% immediately after emulsification production. The encapsulation stability (ES) remained over 90% after 21 days for both systems studied, where 0.1 M NaCl W1 emulsion had a ES of 95.2% and the 0.2 M NaCl W1 emulsion had a ES of 91.1% respectively.
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| 6. |
- Rayner, Marilyn, et al.
(author)
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Quinoa starch granules: a candidate for stabilising food-grade Pickering emulsions.
- 2012
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In: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 92:9, s. 1841-1847
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Journal article (peer-reviewed)abstract
- BACKGROUND: Particle-stabilised emulsions, so-called Pickering emulsions, are known to possess many beneficial properties, including being extremely stable. Starch granules isolated from quinoa have been used as emulsion stabilising particles. The granules were intact, 1-3 µm in diameter and modified with octenyl succinic anhydride to increase their hydrophobicity. Starch granules, as opposed to most other particles used to generate Pickering emulsions, are edible, abundant and derived from natural sources. RESULTS: Emulsions produced by high shear homogenisation had droplet sizes of 9-70 µm depending on the starch-to-oil ratio. Droplet size decreased with increasing starch-to-oil ratio, but was unaffected by the oil phase volume over a range of 5-33% oil (v/v). Although the drops were large and subject to creaming, their size remained unchanged over a period of 7 days. By adjusting the starch-to-oil ratio drops could be made to be buoyancy neutral to prevent creaming. Rheological characterisation indicated a gel structure with an elastic modulus in the range 200-2000 Pa depending on droplet size. CONCLUSION: This work has demonstrated the successful use of starch granules to stabilise emulsions which may find applications beyond that of food, for example in cosmetics and pharmaceutical formulations. Copyright © 2012 Society of Chemical Industry.
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| 7. |
- Rayner, Marilyn, et al.
(author)
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Quinoa starch granules as stabilizing particles for production of Pickering emulsions
- 2012
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In: Faraday Discussions. - 1364-5498. ; 158, s. 139-155
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Journal article (peer-reviewed)abstract
- Intact starch granules isolated from quinoa (Chenopodium quinoa Willd.) were used to stabilize emulsion drops in so-called Pickering emulsions. Miglyol 812 was used as dispersed phase and a phosphate buffer (pH7) with different salt (NaCl) concentrations was used as the continuous phase. The starch granules were hydrophobically modified to different degrees by octenyl succinic anhydride (OSA) or by dry heat treatment at 120 [degree]C in order to study the effect on the resulting emulsion drop size. The degree of OSA-modification had a low to moderate impact on drop size. The highest level of modification (4.66%) showed the largest mean drop size, and lowest amount of free starch, which could be an effect of a higher degree of aggregation of the starch granules and, thereby, also the emulsion drops stabilized by them. The heat treated starch granules had a poor stabilizing ability and only the starch heated for the longest time (150 min at 120 [degree]C) had a better emulsifying capacity than the un-modified native starch granules. The effect of salt concentration was rather limited. However, an increased concentration of salt slightly increased the mean drop size and the elastic modulus.
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| 8. |
- Timgren, Anna, et al.
(author)
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A model for drop size prediction during cross-flow emulsification
- 2010
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In: Chemical Engineering Research & Design. - : Elsevier BV. - 0263-8762. ; 88:2, s. 229-238
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Journal article (peer-reviewed)abstract
- The formation of drops is a topic of great interest in a wide variety of engineering applications, such as membrane emulsification. In order to develop an improved force balance model that is capable of predicting the final size of the detached drop, the formation of drops into a cross-flowing continuous phase has been studied with computational fluid dynamics (CFD). The force balance developed takes into account the drop deformation that occurs as the drop approaches detachment. The results given by the model have been compared with CFD simulations, and the drop diameters agree within 10%, except at low wall shear stresses. The model has also been compared with experimental results on drop formation using various membranes, cross-flow velocities and surfactants. The difference between the model and experimental results is mainly due to the adsorption of surfactants onto the drop interface and the shape of the membrane pores.
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| 9. |
- Timgren, Anna, et al.
(author)
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Application of the PIV technique to measurements around and inside a forming drop in a liquid–liquid system
- 2008
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In: Experiments in Fluids. - : Springer Science and Business Media LLC. - 1432-1114 .- 0723-4864. ; 44:4, s. 565-575
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Journal article (peer-reviewed)abstract
- A particle image velocimetry (PIV) method has been developed to measure the velocity field inside and around a forming drop with a final diameter of 1 mm. The system, including a microscope, was used to image silicon oil drops forming in a continuous phase of water and glycerol. Fluorescent particles with a diameter of 1 μm were used as seeding particles. The oil was forced through a 200 μm diameter glass capillary into a laminar cross-flow in a rectangular channel. The velocity field was computed with a double-frame cross-correlation function down to a spatial resolution of 21 × 21 μm. The method can be used to calculate the shear stress induced at the interface by the cross-flow of the continuous phase and the main forces involved in the drop formation process.
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| 10. |
- Timgren, Anna, et al.
(author)
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CFD modelling of drop formation in a liquid-liquid system
- 2007
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In: 6th International Conference on Multiphase Flow. - 9783860109137 ; , s. 1-8
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Conference paper (peer-reviewed)abstract
- The formation of an oil drop from a single capillary in a continuous phase flowing perpendicular to the capillary opening has been studied numerically. The shear stress at the interface of the forming drop, the angular velocity inside the drop and the pressure field around the drop have been determined in a cross section of the drop formation area. The results show a maximum pressure in the continuous phase near the stagnation point and a maximum shear stress in both phases nearer the top of the forming drop. The lowest pressures were found behind the top of the drop, where the surrounding flow starts to separate from the interface of the drop. The shear stress outside the drop causes a drag which, together with the drag originated from the pressure field around the drop, promotes drop detachment.
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| 11. |
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| 12. |
- Timgren, Anna, et al.
(author)
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Effects of pore spacing on drop size during cross-flow membrane emulsification—A numerical study
- 2009
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In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388. ; 337, s. 232-239
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Journal article (peer-reviewed)abstract
- The design and pore distribution of the membrane are important factors in cross-flow membrane emulsification. To determine the effects of hydrodynamics and drop interaction on drop size, drop formation has been studied numerically using computational fluid dynamics (CFD). Oil with a viscosity of 7.0 mPa s was used as the dispersed phase and water was used as the continuous phase. The conditions studied were pore spacing of 10, 15 and 20 times the pore diameter (20 μm) at a highly dispersed phase velocity of 0.18 m/s, and 10 times the pore diameter at a low velocity of 0.019 m/s. In the case of short pore separation and a low dispersed phase velocity, the drop formation process was uniform, resulting in an emulsion with a narrow drop size distribution, and a dispersed phase flux of 500 L/m2 h. At the higher dispersed phase velocity, the shortest pore separation gave a polydispersed emulsion, whereas pore separations of 15 and 20 times the pore diameter gave nearly monodispersed emulsions, and the flux of the dispersed phase reached 3400 L/m2 h.
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| 13. |
- Timgren, Anna, et al.
(author)
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Emulsion stabilizing capacity of intact starch granules modified by heat treatment or octenyl succinic anhydride
- 2013
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In: Food Science & Nutrition. - : Wiley. - 2048-7177. ; 1:2, s. 71-157
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Journal article (peer-reviewed)abstract
- Starch granules are an interesting stabilizer candidate for food-grade Pickering emulsions. The stabilizing capacity of seven different intact starch granules for making oil-in-water emulsions has been the topic of this screening study. The starches were from quinoa; rice; maize; waxy varieties of rice, maize, and barley; and high-amylose maize. The starches were studied in their native state, heat treated, and modified by octenyl succinic anhydride (OSA). The effect of varying the continuous phase, both with and without salt in a phosphate buffer, was also studied. Quinoa, which had the smallest granule size, had the best capacity to stabilize oil drops, especially when the granules had been hydrophobically modified by heat treatment or by OSA. The average drop diameter (d 32) in these emulsions varied from 270 to 50 μm, where decreasing drop size and less aggregation was promoted by high starch concentration and absence of salt in the system. Of all the starch varieties studied, quinoa had the best overall emulsifying capacity, and OSA modified quinoa starch in particular. Although the size of the drops was relatively large, the drops themselves were in many instances extremely stable. In the cases where the system could stabilize droplets, even when they were so large that they were visible to the naked eye, they remained stable and the measured droplet sizes after 2 years of storage were essentially unchanged from the initial droplet size. This somewhat surprising result has been attributed to the thickness of the adsorbed starch layer providing steric stabilization. The starch particle-stabilized Pickering emulsion systems studied in this work has potential practical application such as being suitable for encapsulation of ingredients in food and pharmaceutical products.
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| 14. |
- Timgren, Anna
(author)
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Numerical and Experimental Studies on the Effects of Flow on Drop Formation in Cross-flow Membrane Emulsification
- 2009
-
Doctoral thesis (other academic/artistic)abstract
- Membrane emulsification is a gentle process that produces emulsions with a narrow drop size distribution, which increases the stability of the emulsion. The dispersed phase is forced through the pores in a membrane and drops are formed at the other side of the membrane where a continuous phase, flowing along the membrane surface, sweeps away the forming drops. The growth and detachment of drops is a complex phenomenon that is dependent on the process conditions, which affect the size of the drops and the drop formation time. The main objective with the project work presented in this thesis was to develop experimental and numerical tools for investigation of the effects of selected process conditions. The particle image velocimetry technique was used to measure the velocity field inside and around a drop during formation from a single pore with a diameter of 200 µm. The system included a microscope and an objective with a narrow focal depth that made measurements possible in a cross-section of the drop formation volume when the two liquids had matching refractive indices. The drop formation process was also modeled with the computational fluid dynamics (CFD) program Fluent. The drop formation time and the size of the detached drop were used as validation parameters and the results from the two methods corresponded well, with a difference of less than 5% for the drop formation time and the drop diameter. The cross-flow velocity has a major impact on drop size, which decreases as the cross-flow increases. An increase in cross-flow, oil viscosity and pore pressure displace the position of necking and drop detachment away from the pore opening, which will have a decreasing effect on the final size of the drop. A force balance model that takes into account the drop deformation that occurs as the drop approaches detachment was developed. The results given by the model was compared with CFD simulations, and the drop diameters agreed within 10%, except at low wall shear stresses. The model was also compared with experimental results on drop formation using various membranes, cross-flow velocities and surfactants. The difference between the model and experimental results is mainly due to the adsorption of surfactants onto the drop interface and the shape of the membrane pores. The effects of hydrodynamics and drop interaction on drop size were determined by studying simultaneous drop formation using CFD. The conditions studied were pore spacing of 10, 15 and 20 times the pore diameter (20 µm) at a highly dispersed phase velocity of 0.18 m/s, and 10 times the pore diameter at a low velocity of 0.019 m/s. In the case of short pore separation and a low dispersed phase velocity, the drop formation process was uniform, resulting in an emulsion with a narrow drop size distribution. At the higher dispersed phase velocity, the shortest pore separation gave a polydispersed emulsion, whereas larger pore separations gave nearly monodispersed emulsions.
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| 15. |
- Timgren, Anna, et al.
(author)
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PIV and CFD measurements of internal velocity in a forming drop in a liquid-liquid system
- 2007
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In: 7th International Symposium on Particle Image Velocimetry. ; , s. 1-10
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Conference paper (peer-reviewed)abstract
- A PIV method has been used to determine the internal motion in an oil drop during formation and to validate a numerical simulation of the drop formation process. The PIV system included a microscope attached to the camera, which gave a focal depth of 50 µm and a possibility to measure the velocity in the centre cross section of the drop. Oil was forced through a capillary with a diameter of 200 µm into a channel with a cross-flowing continuous phase that induced a shear at the interface of the forming drop, which resulted in a rotational motion inside the drop. The angular velocity in the drop reached a maximum after 1/4 of the drop formation time and approached a steady state before drop detachment when a neck was formed above the capillary opening. The velocity of oil out of the capillary was also investigated. A clear dependence on the pressure inside the forming drop was obtained.
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| 16. |
- Timgren, Anna, et al.
(author)
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Starch particles for food based Pickering emulsions
- 2011
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In: Procedia Food Science. - : Elsevier BV. - 2211-601X. ; 1, s. 95-103
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Journal article (peer-reviewed)abstract
- Intact starch granules are a new source of particles for stabilizing emulsions, so called Pickering emulsions. Small (1-2 μm) and uni-modal starch granules at various concentrations have been used in this study to investigate the stability of the emulsions, the drop size dependence of the starch concentration and the barrier properties of the stabilizing starch layer upon heating. The granules were modified with octenyl succinic anhydride (OSA) to increase the hydrophobicity. The drops in the emulsions prepared in this study were in the 10-100 μm range depending on the starch concentration, and the drop size decreased with an increased amount of added starch granules. During the 8 week storage, the emulsion drops were stable to coalescence and the volume occluded by the emulsion phase was unaffected or even increased. In order to increase the barrier properties at the oil-water interface the emulsions were gently heated, which induced a partial gelatinization of the starch granules. The efficiency of the barrier was characterized by a lipolysis experiment where the activity of lipase was measured. The activity of lipase was decreased with nearly 70% compared to an unheated starch stabilized emulsion, which will be useful in applications where a controlled release of specific substances in the gastro intestinal tract is desirable.
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