The enzyme laccase is a copper-containing oxidoreductase with the ability to oxidize a wide range of substrates, such as ferulic acid. Thus, the ferulic acid-containing sugar beet pectin (SBP) can be cross-linked through laccase-mediated oxidation. As cross-linking increases viscosity, it could be applied to stabilize SBP-containing foams. In this study, laccase-mediated cross-linking of SBP was investigated under conditions of a high-pressure foaming process. Shear, presence of CO₂, and pressure were simulated in a rheometer equipped with a high-pressure cell. At rest, addition of laccase to SBP solution led to the formation of a stiff gel. Application of shear upon mixing of laccase and SBP solution decreased the storage modulus with increasing shear duration and shear rate. This can be attributed to the formation of a fluid gel. However, when shear was stopped before all available ferulic acid groups were cross-linked, a stronger and more coherent network was formed. Pressure exerted by CO₂ did not affect cross-linking. Additionally, this approach was tested in a stirred high-pressure vessel where SBP was foamed through CO₂ dissolution under pressure and shear followed by controlled pressure release. While pure SBP foam was highly unstable, addition of laccase decelerated collapse. Highest stability was reached when laccase and SBP were mixed prior to depressurization. At the point of foam formation, the continuous phase was thereby viscous enough to increase foam stability. At the same time, continuation of cross-linking at rest caused gel templating of the foam structure.

中文翻译：

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果胶在高压发泡过程中的酶促交联

漆酶是一种含铜的氧化还原酶，具有氧化多种底物（如阿魏酸）的能力。因此，含阿魏酸的甜菜果胶（SBP）可以通过漆酶介导的氧化交联。当交联增加粘度时，可用于稳定含SBP的泡沫。在这项研究中，在高压发泡条件下研究了漆酶介导的SBP交联。剪切，CO _2的存在，并在配备高压电池的流变仪中模拟压力。静止时，将漆酶添加到SBP溶液中导致形成坚硬的凝胶。在漆酶和SBP溶液混合时施加剪切力会随着剪切持续时间和剪切速率的增加而降低储能模量。这可以归因于流体凝胶的形成。但是，在所有可用的阿魏酸基团交联之前停止剪切时，会形成一个更牢固且更紧密的网络。CO ₂施加的压力不影响交联。此外，该方法在搅拌高压容器中进行了测试，在该容器中SBP通过CO ₂发泡在压力和剪切力下溶解，然后控制压力释放。尽管纯净的SBP泡沫非常不稳定，但添加漆酶可降低塌陷。在降压之前将漆酶和SBP混合时，可以达到最高的稳定性。因此在泡沫形成点，连续相足够粘稠以增加泡沫稳定性。同时，静止时交联的继续引起泡沫结构的凝胶模板。