Control of surface properties and efficiency of some antifoaming agents used in beet sugar manufacturing

摘要

In a sugar factory, foam formation occurs at all stages of processing, beginning with beet washing. In this work different antifoaming agents were compared by studying their mechanism of action and optimizing the most efficient doses. The relative efficacy of six samples of antifoaming agents was determined as a function of concentration and temperature. It was shown that the efficiency increases with concentration and exhibits a threshold. The effect of temperature resides in the need that antifoaming agents are added at a temperature above the turbidity (cloud point). Likewise, antifoaming agents were classified as a function of their hydrophobicity and efficiency at normal temperature. It was shown that efficiency increases with hydrophobicity. The more efficient an antifoaming agent, the slower its adsorption at the air/liquid interface. A mechanism of trapping of juice surface-active molecules by antifoaming agents is proposed. Finally, adsorption kinetics were studied at high temperature forantifoaming agents which were quickly adsorbed at normal temperature. It was found that increasing temperature facilitates the adsorption of antifoaming agents at the interface. Such an adsorption is the more important the more efficient the antifoamingagents at normal temperature. A decrease in the activation energy for the adsorption of antifoaming agents from subsurface to interface was proposed as a possible explanation of antifoaming agent behavior at interfaces.