Influence of pH and salt concentration on the emulsifying properties of native wheat gliadins and of their chymotryptic hydrolysates

Chymotryptic hydrolysates with degrees of hydrolysis around 1% were prepare d from purified beta- and gamma-gliadins of wheat. Some functional properti es were studied at pH 4.0 and 6.5 in the absence or in the presence of 1% a nd 2% NaCl. The hydrolysates were highly soluble in all the conditions of p H and salt concentration tested, whereas the solubility of native gliadins did not exceed 20%, except at pH 4.0, 0% NaCl. The differences in emulsifyi ng properties between hydrolysates and native proteins were great in the pr esence of salt. Phase separation was almost complete immediately after emul sification with the native gliadins, but creaming was slowed down and limit ed with the hydrolysates. Furthermore, emulsions stabilized with hydrolysat es showed a very strong resistance to coalescence. Although some difference s were observed between hydrolysates of beta- and gamma-gliadins, the pepti des adsorbed at the alcane/water interface were in both cases the more hydr ophobic and charged, corresponding to the non-repetitive domain of the glia din sequences.