Physicochemical Properties of Food Emulsions

PHYSICOCHEMICAL PROPERTIES OF FOOD EMULSIONS 5.1. Emulsion Stability... 

Many of the unique physicochemical and sensory properties of food emulsions are determined by the presence of the droplets they contain. The most important characteristics of emulsion droplets are therefore discussed below. 

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. 

Weiss, J. 1999. Effect of Mass Transport Processes on Physicochemical Properties of Surfactant-Stabilized Emulsions. Department of Food Science, University of Massachusetts, Amherst. 280. 

Starch is an abundant, inexpensive polysaccharide that is readily available from staple crops such as com or maize and is thus is mostly important as food. Industrially, starch is also widely used in papermaking, the production of adhesives or as additives in plastics. For a number of these applications, it is desirable to chemically modify the starch to increase its hydrophobicity. Starch modification can thus prevent retrodegradation improve gel texture, clarity and sheen improve film formation and stabilize emulsions [108], This may, for example, be achieved by partial acetylation, alkyl siliconation or esterification however, these methods typically require environmentally unfriendly stoichiometric reagents and produce waste. Catalytic modification, such as the palladium-catalyzed telomerization (Scheme 18), of starch may provide a green atom-efficient way for creating chemically modified starches. The physicochemical properties of thus modified starches are discussed by Bouquillon et al. [22]. 

Kanno, C., Shimomura, Y., Takano, E. 1991. Physicochemical properties of milk fat emulsions stabilized with bovine milk fat globule membrane. J. Food Sci. 56, 1219-1223. 

The size of the droplets in an emulsion has a strong influence on many of its physicochemical and sensory properties, e.g., shelf life, appearance, texture, and flavor (1,2, 4). For example, the stability of an emulsion to gravitational separation or droplet aggregation can be greatly improved by decreasing the droplet size. This is because the velocity of sedimentation is proportional to the square of the droplet size. The size of the droplets in an emulsion is largely determined by the emulsifier type and concentration, the physicochemical properties of the component phases, and the homogenization conditions (4). A food manufacturer normally specifies a preestablished desirable droplet size distribution for a particular product. If the product does not meet this specification, it typically must be reprocessed or even discarded. 

Rheological properties. Viscosity, an important physicochemical property of many foods, can be modified by proteins or polysaccharides. The caseins form rather viscous solutions, a reflection of their rather open structure and relatively high water-binding capacity. While the high viscosity of caseinate may be of some importance in casein-stabilized emulsions, it causes production problems for example, due to very high viscosity, not more than about 20% protein can be dissolved even at a high temperature. The low protein content of caseinate solution increases the cost of drying and results in low-density powders which are difficult to handle. 

Demetriades, K., Coupland, J.N. and McClements, D.J. (1997) Physicochemical properties of whey protein stabilized emulsions as affected by heating and ionic strength. /. Food Sci., 62, 462. 

A great number of patents involve the use of CyDs in the formulation of emulsions intended for pharmaceutical, cosmetic, or food products. (Pharmaceutical applications of CyDs are discussed in Chapter 14, while those in cosmetic and food products are presented in Section 16.2.) Unfortunately, most often there is no clear explanation of their role. Of course, sometimes they are used for their ability to include molecules, conferring on them new improved physicochemical properties. In some cases they are presented as stabilizers, without any explanation of the mechanism involved. 

Food scientists are interested in the colloidal properties of emulsions because of their influence on the overall quality and physicochemical properties (texture, stability, appearance, and taste) of products. The emulsion properties most important in determining the bulk properties of the... 

Initially, this chapter will begin with a description of the major factors influencing the formation, physicochemical properties, and stability of oil-in-water emulsions, as this will facilitate the understanding of the influence of water soluble polymers on emulsion characteristics. The physicochemical basis of the surface activity and film forming properties of water soluble polymers will then be covered. Finally, the characteristics of some of the most important water soluble polymers used as emulsifiers in the food industry will be discussed. 

Khouryieh H, Puli G, Williams K, Aramouni F. Effects of xanthan-locust bean gum mixtures on the physicochemical properties and oxidative stability of whey protein stabilised oil-in-water emulsions. Food Chem. 167 340-348,2015. 

Proteins are the most important foams and emulsifiers used in food technology since they fulfill both a practical and a nutritional aspect. Often, surfactants and polymers are added to the system to improve its stability. Food dispersions can be very complex, such as solid foams, in which the system is solidified after heating, such as cakes or bread, or after freezing, such as ice creams. Furthermore, ice creams are even more complex since they consist of foam made from an emulsion. However, this chapter is devoted to the study of the structure of foams and emulsions on the basis of their fundamental physicochemical properties. Hence, we will focus on liquid foams and emulsions. 

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