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Bubble inclusion is one of the fastest growing operations practiced in the food industry. A variety of aerated foods is currently available in supermarkets, and newer products are emerging all the time. This paper aims to combine knowledge on chocolate aeration with studies performed on bubble formation and dispersion characteristics. More specifically, we have investigated bubble formation induced by applying vacuum. Experimental methods to determine gas hold-up (volume fraction of air), bubble section distributions along specific planes, and chocolate rheological properties are presented. This study concludes that decreasing pressures elevate gas hold-up values due to an increase in the number of bubble nuclei being formed and release of a greater volume of dissolved gases. Furthermore, bubbles are observed to be larger at lower pressures for a set amount of gas because the internal pressure needs to be in equilibrium with the surrounding pressures. Temperature-induced changes to the properties of the chocolate have less of an effect on bubble formation. On the other hand, when different fats and emulsifiers are added to a standard chocolate recipe, milk fat was found to increase, significantly, the gas hold-up values and the mean bubble-section diameters. It is hypothesized that this behavior is related to the way milk fats, which contain different fatty acids to cocoa butter, crystallize and influence the setting properties of the final product. It is highlighted that apparent viscosity values at low shear rate, as well as setting behavior, play an important role in terms of bubble formation and entrainment.

Protein partitioning kinetics was measured for the semibatch extraction of lysozyme in a laboratory-scale, liquid-liquid spray column. The organic, isooctane phase contained reverse micelles formed from the anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate. For the extraction of protein fi om aqueous to reverse micellar phases, experiments were performed over a range of dispersed-phase flow rates for cases of the organic- or aqueous-phase dispersion. The influence of aqueous-phase pH and ionic strength, which influence electrostatic interactions between protein and reverse micelles, was also investigated. Results were interpreted in terms of a two-film model of mass transfer. The nature of the dispersed phase could significantly influence the partitioning kinetics, while study of the droplet hydrodynamics suggested that stagnant drops were formed regardless of which phase was dispersed. Literature correlations for describing the droplet-formation process and droplet hydrodynamics predicted measured values satisfactorily. Attempts were also made to predict overall mass-transfer coefficients based on existing correlations describing mass transfer during droplet formation, free rise (or fall), and coalescence. Predicted values of K-L were 2-10 times greater than measured values, probably because of large concentrations of surfactant used to formulate the reverse micelle phases. This approach did, however, provide detailed information on the quantity of protein transferred during the successive processes of droplet formation, fi ee rise (or fall) and coalescence.