| 1. |
- Tornberg, Eva, et al.
(författare)
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Functional Characterization of Protein Stabilized Emulsions: Effect of Processing.
- 1977
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Ingår i: Journal of Food Science. - : Wiley. - 0022-1147 .- 1750-3841. ; 42:2, s. 468-472
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Tidskriftsartikel (refereegranskat)abstract
- In order to evaluate the emulsifying characteristics of a protein the effect of processing of a protein stabilized soybean oil‐in‐water emulsion on the creaming stability of the emulsion was investigated. Three protein systems were used, namely soybean protein isolate, sodium caseinate and whey protein concentrate (WPC). The effects of four different types of emulsifying equipment, an ultra‐turrax, a Sorvall omnimixer, a valve homogenizer and an ultrasonic apparatus were studied. It was found that the type of emulsifying apparatus, the emulsifying time and intensity had a marked influence on the properties of the protein stabilized emulsions. It was demonstrated for all the types of apparatus and proteins used, that by increasing emulsifying intensity and time better emulsions, when characterized by the creaming method, are obtained up to a certain limit whereupon there is nothing to be gained by an additional increase of these factors. The necessary emulsifying intensity and time to obtain a certain stability range differed considerably according to the various proteins investigated as well as environmental conditions. This intensity‐time dependence may be considered as an emulsifying characteristic of the protein.
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| 2. |
- Tornberg, Eva
(författare)
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Functional Characterization of Protein Stabilized Emulsions: Emulsifying Behaviour of Proteins in a Valve Homogenizer.
- 1978
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 29:10, s. 867-879
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Tidskriftsartikel (refereegranskat)abstract
- Protein stabilised emulsions have been prepared in a valve homogeniser incorporated into a recirculating emulsification system, where the power input and number of passes have been varied. The food proteins studied were a soy‐bean protein isolate, a whey protein concentrate (WPC) and a sodium caseinate. The emulsions obtained were characterized in terms of particle size distribution and amount of protein adsorbed on to the fat surface (protein load). Generally, the final fat surface area of the emulsions obtained increases more as a function of power input than as a function of number of passes. Distribution width, cs, decreases mostly with increasing power supply and number of passes, but at the highest power input cs increases. The protein load on the fat globules is largely determined by the fat surface area and by the type of protein adsorbed. The soy proteins give a high protein load and the caseinates give a low protein adsorption at small fat surface areas created. This relation is reversed at large surface areas of the fat globules. The relation between percentage protein adsorbed from bulk as a function of surface area suggests that the caseinates mainly cover the newly created interface by adsorption from the bulk, whereas the soy proteins fulfil this task mostly by spreading at the interface. Salt addition to 0.2M‐NaCl enhances protein adsorption at the fat globule interface in the case of soy protein and caseinate, but for the whey proteins protein load is higher in distilled water.
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| 3. |
- Tornberg, Eva
(författare)
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Functional Characterization of Protein Stabilized Emulsions: Standardized Emulsifying Procedure.
- 1978
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Ingår i: Journal of Food Science. - : Wiley. - 0022-1147 .- 1750-3841. ; 43:5, s. 1553-1558
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Tidskriftsartikel (refereegranskat)abstract
- Dr. Anne‐Marie Hermansson is heartily thanked for her kind interest in this work, and Dr. P. Walstra is thanked for his valuable comments. The authors are also much indebted to Ing. Ernst Braun for valuable advice during the construction of the emulsifying apparatus and for making the construction drawings. The practical construction work of the valve homogenizer and the ultra‐turrax by Jan Walter and Sune Jonsson, respectively, is gratefully acknowledged. The authors also thank Mr. Dennis Jansson for the construction of the electronic unit of the calorimeter. The investigations were made possible by grants from the Swedish Board for Technical Development. and this financial support is gratefully acknowledged.
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| 4. |
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| 5. |
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| 6. |
- Tornberg, Eva
(författare)
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Protein som emulgator.
- 1979
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Ingår i: KEMISK TIDSKRIFT. - 0039-6605. ; 91:4, s. 24-24
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 7. |
- Tornberg, Eva
(författare)
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The Adsorption Behavior of Proteins at an Interface as related to their Emulsifying Properties
- 1979
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Ingår i: Functionality and Protein Structure. - WASHINGTON, D. C. : AMERICAN CHEMICAL SOCIETY. - 9780841204782 - 9780841206151 ; 92, s. 105-123
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Konferensbidrag (refereegranskat)abstract
- The emulsifying properties of proteins have been a subject concern for those dealing with functional properties of proteins. The studies so far have been restricted to two main approaches: emulsifying capacity and emulsion stability measurements. The former measures the maximum oil addition until inversion or phase separation of the emulsion occurs, whereas the latter measures the ability of the emulsion to remain unchanged. variety of empirical methods has been used, which makes it difficult to compare the results obtained by different authors. Not only methods of measurement vary, but also the way the emulsions are prepared, which strongly influences the properties of emulsions formed (1). As protein stabilized emulsions are usually very stable and the adsorption of proteins at interfaces can be considered as mainly irreversible, the emulsifying properties of the proteins during the emulsification process become increasingly important in determining the properties of the emulsion formed.
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| 8. |
- Tornberg, Eva
(författare)
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The Application of the Drop Volume Technique to Measurements of the Adsorption of Proteins at Interfaces.
- 1978
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Ingår i: Journal of Colloid and Interface Science. - 1095-7103. ; 64:3, s. 391-402
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Tidskriftsartikel (refereegranskat)abstract
- A new procedure for the application of the drop volume technique to measurements of the rate of adsorption of proteins at interfaces has been developed. The mode of adsorption of the proteins lysozyme, β-lactoglobulin and bovine serum albumin (BSA) at the air-water interface has been measured with the drop volume method and has been compared to measurements with the Wilhelmy plate technique. Due to surface enlargement of the drop throughout the process of the surface tension decay, slower kinetics of the adsorption process is obtained by the drop volume method compared to the Wilhelmy plate technique, and the proteins investigated were differently sensitive to this surface expansion. The adsorption process of the proteins has been evaluated in terms of different rate-determining processes. Different intermediate states between the native and the denatured forms have been observed.
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| 9. |
- Tornberg, Eva
(författare)
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The Interfacial Behaviour of Three Food Proteins Studied by the Drop Volume Technique.
- 1978
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 29, s. 762-762
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption behaviour of three food proteins, a soy protein isolate, a sodium casein‐ate and a whey protein concentrate, at the air‐water interface has been studied by the drop volume method. The kinetics of surface tension decay were evaluated in terms of different rate‐determining steps at different ionic strengths and concentrations. This analysis indicates the following characteristics concerning the surface behaviour of the protein systems studied. The soy proteins diffuse slowly to the interface compared to the other proteins, probably due to the large particle size of the association complex of soy proteins. For the soy proteins, diffusion is slower in distilled water than in 0.2M‐NaCl solution and spreading of molecules at the interface is most easily performed in 0.2M‐NaCl solution. The whey proteins diffuse quickly to the interface, which is in accordance with their aqueous association; mainly small molecular complexes. Diffusion is slower and spreading easier in distilled water than in 0.2M‐NaCl solution. Although the caseinate has a complex quaternary structure, like the soy proteins, it has a very different surface behaviour. The diffusion step is rapid at concentrations above 10−3 wt % and contributes to a large extent to the interfacial tension decay, especially when the caseinate is dispersed in 0.2M‐NaCl solution. At a concentration of 10−3 wt % and below, the rate of the diffusion step is slowed down drastically, with an accompanying drop in the surface activity of the protein. This type of surface behaviour can be explained if the migration of the caseinates to the interface takes place via the casein monomers in the bulk phase.
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