and emulsification (8)(9)(10)(11)(12). Shimada et al. (7) showed that Surface active gelatins were formed by covalent attachment of enzymatically modified gelatins reduced surface tension hydrophobic groups to gelatin molecules by reacting N-hydroxymore efficiently than a conventional nonionic surfactant, succinimide esters of various fatty acids (C 4 -C 16 ) with the lysine ethoxylated sorbitan mono stearate. Improvement in surface groups. The surface activity was evaluated by emulsification and tension reduction by chemically modified gelatin was refoaming properties, and by adsorption at the oil-water interface.
ported recently (13), while a linear correlation was found It was found that, in general, the modified gelatins are more surbetween the surface tension at equilibrium and the hydrophoface active than the native gelatin. The increase in hydrophobic bicity index of the modified proteins.
chain length and the number of attached alkyl chains per gelatin
The foaming and emulsifying activities of native and modmolecule leads to a decrease in the emulsion droplet's size and to more stable emulsions. Adsorption isotherms, at the o/w interface, ified gelatins and other proteins were studied by several show much higher surface concentration, at saturation, of the researchers (9-18). Shimada et al. found that the optimal modified gelatin than the native gelatin. The modified gelatins foam stability is obtained by attachment of C 6 alkyl chains. also have high foaming ability and a high foam stability, while Haque and Kito reported that the foaming activity was dethe maximal foam activity is obtained by the C 8 modified gelatin. pendent on the number of the hydrophobic groups attached The foaming properties of the surface-active gelatins were also to the casein molecules, while the foam stability increased compared to that of sodium dodecyl sulfate (SDS) and it was with the increase in the number of attached hydrophobic found that below the CMC of SDS, both foam activity and stability groups (16-18). It was found that the modified casein was were higher for the modified gelatins. On the other hand, above also a better emulsifying agent, while the improvement was the CMC the foam activity of SDS was higher, but the foam obtained even at very low degree of modification, e.g., 0.3 stability was lower than for C 8 -C 16 -modified gelatins. แญง 1998 groups per casein molecule. Magdassi et al. (3) also reported Academic Press