Arabinoxylan networks as affected by ovalbumin content

Solutions (1% w/v) of water-extractable arabinoxylans (WEAX) from wheat were mixed with ovalbumin solutions at different concentrations in order to obtain different protein/polysaccharide ratios (0, 0.6, 2.5, 5.0, 7.5 and 10.0). These mixtures were oxidized by a laccase (Pycnoporus cinnabarinus). The kinetics of gelation was monitored by rheological measurements of the storage modulus (G′) and loss modulus (G″) at 25°C during 2 h. In the different ovalbumin/WEAX mixtures, WEAX cross-linking occurred as shown by an increase in G′. However, final G′ decreased as a function of protein concentration from 17.2 Pa (WEAX) to 7.1 Pa (ovalbumin/WEAX=10), following a sigmoidal relationship. Ovalbumin is probably entrapped in a WEAX covalent network, which explains the changes in rheological properties, but it does not participate in the network formation. Ferulic acid oxidation and diferulic acid formation was delayed at ovalbumin/WEAX=5.0 until 40 min but not at the end of gelation. In the same mixture SH groups from ovalbumin oxidized more rapidly than the protein alone. Ovalbumin via SH groups are probably responsible for the FA oxidation delay and the weaker WEAX gel formed by blocking the enzymatically formed free radicals.