Hydrocolloids, as emulsifiers

Dickinson, E. (2009). Hydrocolloids as emulsifiers and emulsion stabilizers. Food Hydro-colloids, 23, 1473-1482. 

Garti, N. (1999). Hydrocolloids as emulsifying agents for oil-in-water emulsion. Journal of Dispersion Science and Technology, 20, 327-355. 

Akhtar, M., Dickinson, E. (2007). Whey protein-maltodextrin conjugates as emulsifying agents an alternative to gum arabic. Food Hydrocolloids, 21, 607-616. 

Both hydrocolloids and emulsifiers increase the water-binding capacity in the mix (increased % of hydrogen atoms with low T2 and decreased T2 values). A synergistic effect is observed when both ingredients are present. From studies described earlier in this chapter, the effect of hydrocolloids is assumed to be due to simple water binding and increased thickness of protein layers around the fat globules, whereas the effect of emulsifiers may be due to the increased hydration of interfacially bound protein as well as increased hydration of polar groups of emulsifier at the oil-water interface. 

The dough strengtheners which are used most often are DATEM (diacetyl tartaric esters of monoglycerides) and stearoyl lactylates. Lecithins are also used as emulsifiers. DATEM, however, is superior so far as the bread volume is concerned (Adams et al., 1991). Hydrocolloids may also improve the dough strength. The subject has been cautiously considered in several articles by Mettler et al. (1991). 

Many food emulsions are stabilized by surface-active polymers that adsorb to droplet surfaces and form protective membranes. Some of these functional polymers are integral components of more complex food ingredients used in food manufacture (e.g. milk, eggs, meat, fish, and flour), whereas others have been isolated from their normal environments and possibly modified before being sold as specialty ingredients (e.g. protein concentrates or isolates, hydrocolloid emulsifiers). In this section, we will focus primarily on those surface-active polymers that are sold as functional ingredients specifically designed for use as emulsifiers in foods. 

Many food formulations contain mixtures of surfactants (emulsifiers) and hydrocolloids. Interaction between the surfactant and polymer molecule plays a major role in the overall interaction between the particles or droplets, as well as the bulk rheology of the whole system. Such interactions are complex and require fundamental studies of their colloidal properties. As discussed later, many food products contain proteins that are used as emulsifiers. Interaction between proteins and hydrocolloids is also very important in determining the interfacial properties and bulk rheology of the system. In addition, the proteins can also interact with the emulsifiers present in the system and this interaction requires particular attention. 

Several other food emulsions can be quoted, such as coffee whiteners and cake emulsions. Coffee whiteners are O/W emulsions containing vegetable oils and fats covering the size range 1-5 pm and an oil volume fraction of 10-15%. The aqueous continuous phase contains proteins, e.g. sodium casinate, carbohydrates, e.g. maltodextrin, salts and hydrocolloids. The emulsifying system consists of blends of nonionic and anionic surfactants with adsorbed protein. 

In the formulation of emulsion systems, one normally distinguishes between two types of ingredients proteins are considered to be the emulsifying agent (or emulsifier) and hydrocolloids are considered to be stabilizers. There is a debate in the hterature as to whether hydrocolloids can serve as emulsifying agents. Several authors claim that except for some specific hydrocolloids (e.g.. 

In addition to the monomeric amphiphiles, many macromolecular amphi-philes exist in the technologist s list of options. Some macromolecules, such as proteins, adsorb onto interfaces and act as emulsifiers, imparting short-term stability. Others, such as hydrocolloids, impart long-term stability, viscosity, or gelation and are termed stabilizers. 

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. 

Sanchez, C.C., Rodriguez Patino, J.M. (2005). Interfacial, foaming and emulsifying characteristics of sodium caseinate as influenced by protein concentration in solution. Food Hydrocolloids, 19, 407 116. 

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. 

The ingredient composition and manufacturing process are important for the different types of whippable emulsions. In many industrially produced whippable emulsions, functional ingredients, such as food emulsifiers and hydrocolloids are used to improve functionality and product stability. 

The interfacially bound protein layer on fat globules is influenced greatly by the emulsifier and hydrocolloid content as well as by processing conditions. 

The desorption of thick protein layers from fat globules of ice cream mix containing emulsifiers and hydrocolloids during ageing and mechanical treatment may also be observed by transmission electron microscopy (Figure 12). The protein bound to the surface of fat globules is desorbed as a tiiick coherent skin23. 

In whippable emulsions with a high fat content, the air-water interface of the foam after whipping is dominated by adsorbed deproteinated fat globules. In whippable emulsions with a low fat content other foam stabilizing mechanisms come into play, such as protein-hydrocolloid and protein-emulsifier interactions. The former subject may be studied by... 

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