EMULSIFICATION AND FOAMING PROPERTIES OF HYDROPHOBICALLY-MODIFIED GELATIN

Surface active gelatins were formed by covalent attachment of hydropho bic groups to gelatin molecules by reacting N-hydroxysuccinimide ester s of various fatty acids (C-4-C-16) With the lysine groups. The surfac e activity was evaluated by emulsification and foaming properties, and by adsorption at the oil-Water interface. It was found that, in gener al, the modified gelatins are more surface active than the native gela tin. The increase in hydrophobic chain length and the number of attach ed alkyl chains per gelatin molecule leads to a decrease in the emulsi on droplet's size and to more stable emulsions. Adsorption isotherms, at the o/w interface, show much higher surface concentration, at satur ation, of the modified gelatin than the native gelatin. The modified g elatins also have high foaming ability and a high foam stability, whil e the maximal foam activity is obtained by the C-8 modified gelatin. T he foaming properties of the surface-active gelatins were also compare d to that of sodium dodecyl sulfate (SDS) and it was found that below the CMC of SDS, both foam activity and stability were higher for the m odified gelatins. On the other hand, above the CMC the foam activity o f SDS was higher, but the foam stability was lower than for C-8-C-16-m odified gelatins. (C) 1998 Academic Press.