Surfactants in the manufacture of foods

In [140], attention is paid to the fact that experiments on the adsorption layer structure of proteins, e.g. milk protein, based on the investigation of adsorption on flat oil-water interfaces do not always adequately reflect the real processes under conditions of emulsion preparation since adsorption proceeds at a higher rate there. At the same time, these investigations predetermine, in many aspects, the choice of compositions for the preparation of emulsions. However, the properties of an emulsifier, such as P-casein, which are studied well enough, cannot be mechanistically transferred to other protein types, e.g. soya. Each protein requires extensive additional studies. 

Dickinson [141] has shown that physical emulsion properties are highly dependent on the structure of the adsorption layers at the surface of dispersed droplets. The structure of the adsorption layers of caseins, e.g. P-casein, considerably differs from the structure of globular  

The structure of adsorption layers is of great importance during preparation of food foams and emulsions. These problems have been studied in [144] for protein adsorption at the liquid/gas interfaces and in [145] for liquid/liquid interfaces. Due attention is also paid to the interaction of typical emulsifiers and proteins during preparation of food emulsions [146 - 147]. Addition of an oil-soluble emulsifier to proteins during preparation of w/o emulsions [146] increased the emulsification rate, but at high concentrations decreased it due to the increase in oil viscosity. In this case, the emulsifier displaced (3-casein from the surface easier than P-lactoglobulin. However, there was no complete displacement into the aqueous phase since multiple emulsions were formed, as mentioned above [142 -143]. Hence, the ehoice of the surfactant/protein ratio is important. 

It has been shown in [147] that aerated model emulsions of palm kernel oil, coconut oil, as well as butter, which are used in making ice-cream can be obtained at an optimum surfactant/protein ratio. A combination of Tween 60 and skimmed milk powder provided a higher stability than using mono- and diglycerides. In particular, this can be due to the fact that Tween 60, at the same time, effectively inhibited the coalescence of gas bubbles. 

Not only emulsifier composition but also the preparation process of the emulsions influence on the stability of food emulsions. It has been shown in [148] that the mode of cooling is a dominating factor. The progressive cooling at room temperature gives a better stability than the brutal cooling with a water bath. 

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