Interactions involved in ovomucin gel-forming properties: a rheological-biochemical approach

Different kinds of interactions involved in the properties of ovomucin gel formation from hen egg white were studied by combining physical and biochemical methods. A decrease in viscosity of the ovomucin gel was observed when it was subjected to chymotrypsin or sonication treatment. The viscosity decrease correlated with a change from non-Newtonian to Newtonian properties of the ovomucin gel. By treatment of the gel with either 5 M guanidinium HCl, 6 M urea, or 5% sodium dodecyl sulfate a change from non-Newtonian to Newtonian properties was also obtained. Although high ionic strength or sialic acid liberation from the ovomucin gel by neuraminidase treatment provoked a decrease in viscosity, it was not followed by a change in non-Newtonian properties. The results obtained suggest that different noncovalent interactions might be involved in gel formation. Electrostatic interactions (partially destroyed by sialic acid removal or 2 M NaCl) and hydrophobic interactions might be responsible for protein-mucin and mucin-mucin interactions. Other bonds susceptible to chymotrypsin treatment and sonication would be involved in the interaction between mucin subunits.