Acid gelation of soluble laccase-crosslinked corn bran arabinoxylan and possible gel formation mechanism
2019
Zhang, Xiaowei | Chen, Tingting | Lim, Jongbin | Gu, Fangting | Fang, Fang | Cheng, Lilin | Campanella, Osvaldo H. | Hamaker, Bruce R.
Here, we reveal a new food gel formed on simple pH reduction of a water-soluble crosslinked corn bran arabinoxylan complex. This is different from low pH gelling high-methoxyl pectin that requires high sugar content, and it is similar in gelling property to low acyl gellan gum though is readily soluble in water. Alkaline-solubilized corn bran arabinoxylan (CAX) with two levels of residual bound ferulic acid was treated with laccase, a crosslinking enzyme, to produce two soluble, crosslinked CAX (SCCAX) complexes of different sizes (avg. 3.5 and 4.5-mer). Both of the SCCAXs formed gels at pH 2, with the larger, more heavily feruloylated SCCAX forming the stronger gel. Gels showed shear-thinning behavior and a thermal and pH reversible property. A gel forming mechanism was proposed to occur through noncovalent crosslinking including hydrogen bonds and hydrophobic interaction among the SCCAX complexes. This mechanism was supported by structural characterization of crosslinked CAX complexes using a Zeta-sizer and FT-IR spectroscopy. Applications of SCCAX gels might be where low pH low sugar gels are desired or a beverage containing SCCAX might be taken with gelling occurring in the low pH environment of the stomach, as well as in other food gels and as a drug delivery matrix.
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