Effect of the Interfacial Layer Composition on the Properties of Emulsion Creams
详细信息 查看全文
- 作者：Alan R. Mackie ; Michael J. Ridout ; Graham Moates ; Fiona A. Husband ; Peter J. Wilde
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2007
- 出版时间：July 11, 2007
- 年：2007
- 卷：55
- 期：14
- 页码：5611 - 5619
- 全文大小：388K
- 年卷期：v.55,no.14(July 11, 2007)
- ISSN：1520-5118
文摘
We have quantified observed differences in the microstructure and rheology of creaming emulsionsstabilized by protein and low molecular weight surfactants. In this study, we made two sets of emulsionsfrom a single parent emulsion, which differed only in their interfacial composition (i.e., either proteinor surfactant). The protein studied was whey protein isolate. The 
rs/zeta.gif" BORDER=0 > potential of the surfactant-stabilizedemulsion was controlled by mixing anionic (SDS) and nonionic (Brij 35) surfactants to match the rs/zeta.gif" BORDER=0 >potential of the protein-stabilized emulsion. Despite this, ultrasonic creaming measurements andconfocal microscopy showed that the structures within the cream layers were different between thetwo sets of emulsions. The protein-stabilized emulsions appeared to slow or arrest the packing withinthe cream, leading to a lower density network of emulsion droplets, whereas the surfactant emulsiondroplets rearranged more quickly into a well-packed, concentrated cream layer. Rheological analysisof the creams showed that despite the protein-stabilized emulsions having a lower dispersed phasevolume fraction, their elastic modulus was approximately 30 times greater than that of a comparablesurfactant-stabilized emulsion. These differences were caused by the ability of the protein to form ahighly viscoelastic interfacial network around the droplets which may include intermolecular covalentcross-links. At close range the adhesive nature of the interaction between the layers contributes tothe microstructure and rheology of concentrated emulsions. This is the first time that such well-defined emulsion systems have been studied in detail both noninvasively to look at the impact oncreaming and also invasively to look at the impact on bulk rheological properties.
rs/zeta.gif" BORDER=0 > potential of the surfactant-stabilizedemulsion was controlled by mixing anionic (SDS) and nonionic (Brij 35) surfactants to match the rs/zeta.gif" BORDER=0 >potential of the protein-stabilized emulsion. Despite this, ultrasonic creaming measurements andconfocal microscopy showed that the structures within the cream layers were different between thetwo sets of emulsions. The protein-stabilized emulsions appeared to slow or arrest the packing withinthe cream, leading to a lower density network of emulsion droplets, whereas the surfactant emulsiondroplets rearranged more quickly into a well-packed, concentrated cream layer. Rheological analysisof the creams showed that despite the protein-stabilized emulsions having a lower dispersed phasevolume fraction, their elastic modulus was approximately 30 times greater than that of a comparablesurfactant-stabilized emulsion. These differences were caused by the ability of the protein to form ahighly viscoelastic interfacial network around the droplets which may include intermolecular covalentcross-links. At close range the adhesive nature of the interaction between the layers contributes tothe microstructure and rheology of concentrated emulsions. This is the first time that such well-defined emulsion systems have been studied in detail both noninvasively to look at the impact oncreaming and also invasively to look at the impact on bulk rheological properties.