Making Dense Covalent Arabinoxylan Gels with High Swelling Properties: A Strategy Based on Water Extraction through Osmotic Compression

Enzymatic oxidation of water-extractable feruloylated arabinoxylan (WEAX) solutions produces covalent irreversible gels that are stable versus time, pH, and T °C. These hydrogels have a huge water holding capacity, which makes them powerful encapsulation matrices. However, the high viscosity of the polymer makes it difficult to prepare concentrated WEAX solutions before gelation as well as impacts the enzymatic efficiency during gelation. This results in low concentrated gels─6% (w/v) max─that are mechanically brittle. In this study, we propose a strategy for producing more concentrated and less fragile hydrogels. It is based on the extraction of water from 1% (w/v) WEAX enzymatic gels using osmotic compression. This approach aims to reinforce the mechanical resistance of the gels before swelling while preserving their covalent network and swelling capacity. WEAX gels were concentrated in this way up to 12–22% (w/v). The compressed gels have viscoelastic properties that are 2 orders of magnitude higher than uncompressed ones. Interestingly, the compression also leads to a slight increase in gel connectivity, presumably through the creation of additional cross-links upon compression. This increase in connectivity has only a small impact on the swelling capacity of the gels, while it has the benefit of increasing their mechanical resistance after swelling. The swollen gels have a homogeneous structure with mesh sizes of ∼200 nm, making them suitable for encapsulation applications. In addition, the compressed gels swell 10–20 times their initial volume, which is another interesting property that may be used for other specific applications.