Enzymatic foam, effect

It is essential to consider the physico-chemical properties of each WPC and casein product in order to effectively evaluate their emulsification properties. Otherwise, results merely indicate the previous processing conditions rather than the inherent functional properties for these various products. Those processing treatments that promote protein denaturatlon, protein-protein Interaction via disulfide interchange, enzymatic modification and other basic alterations in the physico-chemical properties of the proteins will often result in protein products with unsatisfactory emulsification properties, since they would lack the ability to unfold at the emulsion interface and thus would be unable to function. It is recommended that those factors normally considered for production of protein products to be used in foam formation and foam stabilization be considered also, since both phenomena possess similar physico-chemical and functionality requirements (30,31). 

Figure 8. Effect of enzymatic hydrolysis on specific volume of foam obtained by whipping a heated whey protein sol (4% w/w, 85°C, 6 min whipping) (43)...

The effect of temperature satisfies the Arrhenius relationship where the applicable range is relatively small because of low and high temperature effects. The effect of extreme pH values is related to the nature of enzymatic proteins as polyvalent acids and bases, with acid and basic groups (hydrophilic) concentrated on the outside of the protein. Finally, mechanical forces such as surface tension and shear can affect enzyme activity by disturbing the shape of the enzyme molecules. Since the shape of the active site of the enzyme is constructed to correspond to the shape of the substrate, small alteration in the structure can severely affect enzyme activity. Reactor s stirrer speed, flowrate, and foaming must be controlled to maintain the productivity of the enzyme. Consequently, during experimental investigations of the kinetics enzyme catalyzed reactions, temperature, shear, and pH are carefully controlled the last by use of buffered solutions. 

Fig. 5.8 Effect of two soluble yeast extracts (0.25 g/L) on the foaming properties of a model wine. Data presented are the mean of three different experiments. Model wine (control) left) model wine supplemented with the enzymatic extract (middle) and model wine supplemented with the thermal extract (right) (reprinted with permission from Martmez-Rodrfguez et al. 2007)...

Ion specific effects generally follow direct or reverse order of the so-called Hofineister series, which for monovalent anions is, SCN > CIO4 1 > Br- > Cl- > F. In many cases, interfacial effects appear to play a key role. In the simplest case of ions at the air-water interface for example, the specificity is directly reflected in the stability of foams or in the surface tension and surface potential of aqueous salt solutions. In biology, beyond protein crystallisation, the enzymatic activity can be controlled by addition of alkali halides with large differences between fluoride, chloride, bromide, or iodide. Specific types of cations are also identified together with... 

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