Dispersions of commercial casein and whey protein and laboratory-prepared soybean protein were studied in mixed dispersants of water with various aliphatic alcohols, methanol, ethanol, n-propanol and 2-propanol. Supernatant and protein sediments were separated by centrifugation in two steps: 1800 rpm 10 min, followed by centrifugation of the supernatant at 50000 rpm for 60 min (125000xg). A gel-like protein sediment obtained at low alcohol concentration by high-g centrifugation increased in amounts as a function of the alcohol concentration until it progressively transformed, with higher alcohol concentrations, into an opaque flock (precipitate), sedimenting at 1800 rpm. It was concluded that the sediment obtained by ultracentrifugation was a protein of increased density which was produced by partial and progressive dehydration and alcohol binding. The conversion of the sediment into a flock or precipitate is discussed in terms of the hydrophilic-lipophilic balance of the protein and of the polar-nonpolar character of the dispersant.

The emulsifying properties of six commercial milk protein products were studied. The products were separated into one of two groups depending on whether they contained aggregated (micellar) casein or disordered protein (casein or whey protein). Disordered proteins had a greater emulsifying ability than aggregated proteins. Dispersion of aggregated protein in dissociating buffer improved the emulsifying ability. Comparison of emulsion properties in simple oil-in-water emulsions with those in a model coffee whitener formulation showed that the lower emulsifying ability of aggregated protein could be partially compensated by other ingredients.

The effects of cellulose powder and water activity (aw) on the equilibrium water content, glass transition temperature (Tg), mechanical relaxation, and caking of freeze-dried amorphous carbohydrate blend powders (dextrin-glucose mixture) were investigated. Water sorption isotherm and Tg-curve were obtained, and critical water activity (awc) was determined as the aw at Tg = 25 °C. There was a minor effect of cellulose powder on the awc. The degree of caking was negligible below the awc (glassy state), but increased remarkably above the awc (rubbery state). Cellulose powder played a dispersive role in the powder, and thus diminished the degree of caking. The caking behavior could be described by a stretched exponential function, and an experimental formula to predict the degree of caking as a function of aw/awc was obtained. The results for a food powder, with a more complex composition, largely deviated from the formula. Mechanical relaxation was evaluated as a force-reduction during isothermal compression. It was found that the relationship between the degree of caking and force-reduction could be described as a linear function independent of aw and cellulose powder content. The results for the food powder partially followed the linear relationship.