Strain hardening of wheat flour (WF) proteins during fermentation and baking is at the basis of the excellent quality of wheat breads. Yet, there are good reasons to use rye flour (RF), such as its high content of dietary fiber and other bioactives. However, rye proteins lack the ability to form dough with sufficient strain hardening capacity under extension, which partially explains the inferior quality of rye breads. A promising strategy to make high-quality breads with high nutritional value is the use of WF and RF blends. Despite this, the rheological behavior of WF/RF bread doughs has not yet been investigated. This study examines their rheology by non-linear uniaxial extensional and small-amplitude oscillatory shear measurements, and relates these measurements to the quality of the resulting breads. The strain hardening index (SHI), derived from extensional measurements, is expressed as the transient extensional viscosity at maximum strain [η_e⁺(ε_max)] relative to the linear extensional viscosity extrapolated to maximum strain [η_e0⁺(ε_max)]. Both the SHI and bread volume decreased when the level of RF in the blend increased. As an example, replacing 60% WF by RF led to a relative decrease of the SHI and bread volume of 34 and 64%, respectively. The decrease of the SHI is correlated to an increase in η_e0⁺(ε_max). Comparison of the extensional curves of doughs made with blends of WF and RF and doughs made with blends of WF and wheat starch (WS) further revealed that RF components play a major role in the rheology of the doughs. In conclusion, it was found that WF/RF blends need to contain at least 60% WF to obtain bread of proper quality.

中文翻译：

---

由小麦和黑麦面粉混合制成的面包面团的线性和非线性流变学

小麦粉（WF）蛋白质在发酵和烘烤过程中的应变硬化是小麦面包品质卓越的基础。但是，有充分的理由使用黑麦面粉（RF），例如其高含量的膳食纤维和其他生物活性物质。然而，黑麦蛋白质缺乏在延伸下形成具有足够应变硬化能力的生面团的能力，这部分解释了黑麦面包的劣质。制作具有高营养价值的优质面包的一项有前途的策略是使用WF和RF混合物。尽管如此，尚未研究WF / RF面包面团的流变行为。这项研究通过非线性单轴拉伸和小振幅振荡剪切测量方法检查了它们的流变性能，并将这些测量值与所得面包的质量相关联。应变硬化指数（SHI），η _ë ⁺（ε_最大）]相对于线性拉伸粘度外推至最大应变[ η _E0 ⁺（ε_最大）。当掺混物中的RF水平增加时，SHI和面包体积均减少。例如，用RF代替60％的WF可使SHI和面包量分别相对减少34％和64％。所述SHI的降低被关联到在增加η _E0 ⁺（ε_最大）。比较由WF和RF的混合物制得的面团和由WF和小麦淀粉（WS）的混合物制得的面团的拉伸曲线，进一步揭示了RF组分在面团的流变学中起着重要作用。总之，发现WF / RF混合物需要至少包含60％的WF才能获得适当质量的面包。