Temperature foam volume increase rate

As the mass increases in volume due to the production of gas, a competition between the gas pressure and the gel strength of the polymer ensues. If the former is higher than the latter, a point will be reached at which the foam will collapse. The easiest way to demonstrate this is by increasing the temperature. The reason relates to the activation energies of the two reactions (polymerization and abstraction of CO2). If the temperature is increased, the rate of gas evolution increases faster than the polymerization or gelation. 

In Fig. 2 the key parameters are presented for recombinant E. coli batch cultivation in a 60-1 working volume airUft tower loop reactor at constant aeration rate up to 16 h, whereupon the temperature was increased from 30 to 42 °C and gene expression was induced. At the same time concentrated Luxia-Bertani (LB) medium was added to the reactor. To avoid oxygen limitation, the aeration rate was increased (Fig. 2 a). At 12 h the foaming increased and SE9 was added to the medium. The bubble velocities (Fig. 2b) and the specific gas/liquid interfacial area (Fig. 2 c) quickly increased and passed a narrow maximum, but kLa dropped and the OTR was not influenced (Fig. 2d). After the induction of the gene expression by a temperature increase and medium supplement the dissolved oxygen concentration with respect to the saturation increased due to the elevation of the aeration rate (Fig. 2 a) the mean bubble velocity (Fig. 2 b) and specific interfacial area (Fig. 2 c) decreased, OTR increased and kLa remained at low values (Fig. 2d). The mass transfer coefficient with respect to the liquid phase kL dropped from about 1.67 to 0.67 ms after the addition of SE9 to the medium [51]. 

Lather volume depends upon the amount and the type of soap dissolved in the soap liquor during lathering. The mobility of the soap molecules, in addition to their surface properties, contributes to foaming. It is therefore possible that the soaps with very short chains (sodium caprylate and sodium caprate) may have an additional lather benefit. However, the proposed benefit should be restricted to low wash temperatures. The source of the short chain soaps is the coconut or palm kernel oil component of the fat charge. The amount of soap in solution in the wash liquor increases as the level of soluble soap in the bar increases. However, because the lather depends on the very short transient hydration period, it is the amount of soap which goes into solution over this period that is important. This amount also increases as the rates of dissolution of the solid soluble phases of the bar structure increase. 

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