Emulsion stability, effect hydrocolloid stabilizers

Dickinson, E., Matia-Merino, L. (2002). Effect of sugars on the rheological properties of acid caseinate-stabilized emulsion gels. Food Hydrocolloids, 16, 321-331. 

The presence of a thermodynamically incompatible polysaccharide in the aqueous phase can enhance the effective protein emulsifying capacity. The greater surface activity of the protein in the mixed biopolymer system facilitates the creation of smaller emulsion droplets, i.e., an increase in total surface area of the freshly prepared emulsion stabilized by the mixture of thermodynamically incompatible biopolymers (see Figure 3.4) (Dickinson and Semenova, 1992 Semenova el al., 1999a Tsapkina et al., 1992 Makri et al., 2005). It should be noted, however, that some hydrocolloids do cause a reduction in the protein emulsifying capacity by reducing the protein adsorption efficiency as a result of viscosity effects. 

Dickinson, E., Semenova, M.G., Antipova, A.S., Pelan, E. (1998). Effect of high-methoxy pectin on properties of casein-stabilized emulsions. Food Hydrocolloids, 12, 425 432. 

Chuah, A.M., Kuroiwa, T., Kobayashi, I., Nakajima, M. (2009). Effect of chitosan on the stability and properties of modified lecithin stabilized oil-in-water monodisperse emulsion prepared by microchannel emulsification. Food Hydrocolloids, 23, 600-610. 

Sun, C., Gunasekaran, S., Richards, M.P. (2007). Effect of xanthan gum on physicochemical properties of whey protein isolate stabilized oil-in-water emulsions. Food Hydrocolloids, 21, 555-564. 

Kiokias, S. and Bot, A., Effect of protein denaturation on temperature cycling stability of heat-treated acidified protein-stabilised o/w emulsions. Food Hydrocolloids, 19, 493, 2005. 

The authors of this review (46) have used BSA along with monomeric emulsifiers, both in the inner and the outer interfaces (in low concentrations of up to 0.2 wt %), and found significant improvement both in the stability and in the release of markers as compared to the use of the protein in the external phase only (Fig. 13). It was postulated that while the BSA has no stability effect at the inner phase it has strong effect on the release of the markers (mechanical film barrier). On the other hand, BSA together with small amounts of monomeric emulsifiers (or hydrocolloids) serve as good steric stabilizers, improve stability and shelf-life, and slow down the release of the markers. The BSA plays, therefore, a double role in the emulsions as film former and barrier to the release of small molecules at the internal interface, and as steric stabilizer at the external interface. The release mechanisms involving reverse micellar trans-... 

Srinivasan, M., Singh, H. and Munro, P.A. (2000) The effect of sodium chloride on the formation and stability of sodium caseinate emulsions. Food Hydrocolloid., 14,497. 

The stability of an emulsion is increased when additives are added which curtail droplet mobility. This is the basis of the stabilization effect of hydrocolloids (cf. 4.4.3) on o/w emulsions since they increase the viscosity of the outer, aqueous phase. 

Figure 5.8 Schematic representation of three alternative effects of the adsorption of stiff hydrocolloid polymers on the surface of spherical emulsion droplets, depending on the hydrocolloid concentration and the nature of the hydrocolloid-protein interaction (a) A sterically stabilized system, b) an emulsion gel, and (c) a system flocculated by macromolecular bridging (Dickinson, 2003).

Vaziri and Warburton (1994) investigated the effects of different combinations of surfactants (Span 80 and Tween 80) and hydrocolloids (acacia and gelatin) on the release rate and stability of multiple emulsions. The combination of surfactants produced stable systems and more prolonged release because a better interfacial film was formed by the emulsifiers compared with that of the multiple emulsions in which each surfactant was employed individually (see Figure 5.15 and Table 5.3). The enhanced stabilization can also be attributed to the protein content in the acacia gum. The protein provided strong adsorption interaction with the oil-water interface during emulsification. 

The effect of the WPI/xanthan or WPI/modified pectin (MP) (Garti and Wicker, 2005) ratio on stability of W/O/W multiple emulsions was examined (Tables 5.4 and 5.5) Addition of hydrocolloids caused significant improvement, mainly to the multiple emulsion droplet sizes. The droplets were smaller in comparison to droplets of multiple emulsions prepared solely with WPI. Multiple emulsion droplets stabilized with WPI and pectins are one-third the size... 

Are some polysaccharides surface-active, and can they be used as emulsifiers This is a cardinal question still in debate among scientists. Many patents have been filed on methods for preparation of food emulsions with polysaccharides as emulsifiers and stabiUzers. However, close examination of some of theses reports reveals that the stabilization effect can be derived fi om one or both of two possible effects increase in the viscosity of the dispersed phase and/or hydrocolloid surface adsorption. 

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