Shear induced molecular changes of exopolysaccharides from lactic acid bacteria
Shear induced molecular changes of exopolysaccharides from lactic acid bacteria
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DOI：
10.1016/j.foodhyd.2019.105181
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发表时间：
2019-12-01
影响因子：
10.7
通讯作者：
Rohm, Harald
中科院分区：
文献类型：
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作者：
Nachtigall, Carsten;Berger, Christiane;Rohm, Harald
产生外多糖（EPS）的乳酸菌对发酵乳制品的质地有积极的影响，它们的高水结合能力导致流变学的变化和协同作用的减少。在生产过程中，剪切会影响产品的质地，对EPS的性能有未知的影响。通过对来自嗜热链球菌DGCC7710或葡聚糖的增粘EPS水溶液进行微流化器、细胞破坏系统或齿形环分散单元的剪切处理，以施加不同的能量输入，我们研究了溶液中的大分子性质和行为。尽管共价键断裂，波谱核磁共振分析显示，重复单元结构保持不变，而大分子性质的变化，如固有粘度、水动力体积和分子质量强烈依赖于能量输入。多糖溶液动态粘度的降低与观察到的分子质量的减少显著相关，EPS对酸性凝胶形成过程中凝胶刚度的贡献等技术功能特性的影响也受到影响。因此，结果表明，应该考虑通过剪切输入的机械能，因为产品的质地可能会因EPS分子的机械分解而改变。
Exopolysaccharide (EPS) producing lactic acid bacteria are known for their positive effect on the texture of fermented dairy products, with their high water binding capacity causing changes in rheology and syneresis reduction. During manufacture, product texture is affected by shearing with an unknown impact on the properties of the EPS. By subjecting aqueous solutions of viscosity enhancing EPS from Streptococcus thermophilus DGCC7710 or dextran to defined shear treatments with a Microfluidizer, a cell disruption system or a toothed ring dispersion unit to apply different energy input, we investigated macromolecular properties and the behaviour in solution. Despite the breakage of covalent bonds, spectroscopic NMR analyses revealed that repeating unit structure remained unchanged, whereas changes in macromolecular properties such as intrinsic viscosity, hydrodynamic volume, and molecular mass strongly depended on energy input. The decrease of the dynamic viscosity of the polysaccharide solutions was significantly related to the observed decrease in molecular mass, and the impact of the EPS on technofunctional properties such as contribution to gel stiffness during acid gel formation was also affected. The results therefore indicate that mechanical energy input through shearing should be considered because product texture may be altered as a consequence of a mechanical breakdown of EPS molecules.